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-rw-r--r--Documentation/PCI/acpi-info.rst192
-rw-r--r--Documentation/PCI/boot-interrupts.rst159
-rw-r--r--Documentation/PCI/endpoint/function/binding/pci-test.rst26
-rw-r--r--Documentation/PCI/endpoint/index.rst15
-rw-r--r--Documentation/PCI/endpoint/pci-endpoint-cfs.rst118
-rw-r--r--Documentation/PCI/endpoint/pci-endpoint.rst231
-rw-r--r--Documentation/PCI/endpoint/pci-test-function.rst103
-rw-r--r--Documentation/PCI/endpoint/pci-test-howto.rst235
-rw-r--r--Documentation/PCI/index.rst20
-rw-r--r--Documentation/PCI/msi-howto.rst287
-rw-r--r--Documentation/PCI/pci-error-recovery.rst426
-rw-r--r--Documentation/PCI/pci-iov-howto.rst172
-rw-r--r--Documentation/PCI/pci.rst577
-rw-r--r--Documentation/PCI/pcieaer-howto.rst300
-rw-r--r--Documentation/PCI/pciebus-howto.rst220
-rw-r--r--Documentation/PCI/sysfs-pci.rst138
16 files changed, 3219 insertions, 0 deletions
diff --git a/Documentation/PCI/acpi-info.rst b/Documentation/PCI/acpi-info.rst
new file mode 100644
index 000000000..060217081
--- /dev/null
+++ b/Documentation/PCI/acpi-info.rst
@@ -0,0 +1,192 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================================
+ACPI considerations for PCI host bridges
+========================================
+
+The general rule is that the ACPI namespace should describe everything the
+OS might use unless there's another way for the OS to find it [1, 2].
+
+For example, there's no standard hardware mechanism for enumerating PCI
+host bridges, so the ACPI namespace must describe each host bridge, the
+method for accessing PCI config space below it, the address space windows
+the host bridge forwards to PCI (using _CRS), and the routing of legacy
+INTx interrupts (using _PRT).
+
+PCI devices, which are below the host bridge, generally do not need to be
+described via ACPI. The OS can discover them via the standard PCI
+enumeration mechanism, using config accesses to discover and identify
+devices and read and size their BARs. However, ACPI may describe PCI
+devices if it provides power management or hotplug functionality for them
+or if the device has INTx interrupts connected by platform interrupt
+controllers and a _PRT is needed to describe those connections.
+
+ACPI resource description is done via _CRS objects of devices in the ACPI
+namespace [2].   The _CRS is like a generalized PCI BAR: the OS can read
+_CRS and figure out what resource is being consumed even if it doesn't have
+a driver for the device [3].  That's important because it means an old OS
+can work correctly even on a system with new devices unknown to the OS.
+The new devices might not do anything, but the OS can at least make sure no
+resources conflict with them.
+
+Static tables like MCFG, HPET, ECDT, etc., are *not* mechanisms for
+reserving address space. The static tables are for things the OS needs to
+know early in boot, before it can parse the ACPI namespace. If a new table
+is defined, an old OS needs to operate correctly even though it ignores the
+table. _CRS allows that because it is generic and understood by the old
+OS; a static table does not.
+
+If the OS is expected to manage a non-discoverable device described via
+ACPI, that device will have a specific _HID/_CID that tells the OS what
+driver to bind to it, and the _CRS tells the OS and the driver where the
+device's registers are.
+
+PCI host bridges are PNP0A03 or PNP0A08 devices.  Their _CRS should
+describe all the address space they consume.  This includes all the windows
+they forward down to the PCI bus, as well as registers of the host bridge
+itself that are not forwarded to PCI.  The host bridge registers include
+things like secondary/subordinate bus registers that determine the bus
+range below the bridge, window registers that describe the apertures, etc.
+These are all device-specific, non-architected things, so the only way a
+PNP0A03/PNP0A08 driver can manage them is via _PRS/_CRS/_SRS, which contain
+the device-specific details.  The host bridge registers also include ECAM
+space, since it is consumed by the host bridge.
+
+ACPI defines a Consumer/Producer bit to distinguish the bridge registers
+("Consumer") from the bridge apertures ("Producer") [4, 5], but early
+BIOSes didn't use that bit correctly. The result is that the current ACPI
+spec defines Consumer/Producer only for the Extended Address Space
+descriptors; the bit should be ignored in the older QWord/DWord/Word
+Address Space descriptors. Consequently, OSes have to assume all
+QWord/DWord/Word descriptors are windows.
+
+Prior to the addition of Extended Address Space descriptors, the failure of
+Consumer/Producer meant there was no way to describe bridge registers in
+the PNP0A03/PNP0A08 device itself. The workaround was to describe the
+bridge registers (including ECAM space) in PNP0C02 catch-all devices [6].
+With the exception of ECAM, the bridge register space is device-specific
+anyway, so the generic PNP0A03/PNP0A08 driver (pci_root.c) has no need to
+know about it.  
+
+New architectures should be able to use "Consumer" Extended Address Space
+descriptors in the PNP0A03 device for bridge registers, including ECAM,
+although a strict interpretation of [6] might prohibit this. Old x86 and
+ia64 kernels assume all address space descriptors, including "Consumer"
+Extended Address Space ones, are windows, so it would not be safe to
+describe bridge registers this way on those architectures.
+
+PNP0C02 "motherboard" devices are basically a catch-all.  There's no
+programming model for them other than "don't use these resources for
+anything else."  So a PNP0C02 _CRS should claim any address space that is
+(1) not claimed by _CRS under any other device object in the ACPI namespace
+and (2) should not be assigned by the OS to something else.
+
+The PCIe spec requires the Enhanced Configuration Access Method (ECAM)
+unless there's a standard firmware interface for config access, e.g., the
+ia64 SAL interface [7]. A host bridge consumes ECAM memory address space
+and converts memory accesses into PCI configuration accesses. The spec
+defines the ECAM address space layout and functionality; only the base of
+the address space is device-specific. An ACPI OS learns the base address
+from either the static MCFG table or a _CBA method in the PNP0A03 device.
+
+The MCFG table must describe the ECAM space of non-hot pluggable host
+bridges [8]. Since MCFG is a static table and can't be updated by hotplug,
+a _CBA method in the PNP0A03 device describes the ECAM space of a
+hot-pluggable host bridge [9]. Note that for both MCFG and _CBA, the base
+address always corresponds to bus 0, even if the bus range below the bridge
+(which is reported via _CRS) doesn't start at 0.
+
+
+[1] ACPI 6.2, sec 6.1:
+ For any device that is on a non-enumerable type of bus (for example, an
+ ISA bus), OSPM enumerates the devices' identifier(s) and the ACPI
+ system firmware must supply an _HID object ... for each device to
+ enable OSPM to do that.
+
+[2] ACPI 6.2, sec 3.7:
+ The OS enumerates motherboard devices simply by reading through the
+ ACPI Namespace looking for devices with hardware IDs.
+
+ Each device enumerated by ACPI includes ACPI-defined objects in the
+ ACPI Namespace that report the hardware resources the device could
+ occupy [_PRS], an object that reports the resources that are currently
+ used by the device [_CRS], and objects for configuring those resources
+ [_SRS]. The information is used by the Plug and Play OS (OSPM) to
+ configure the devices.
+
+[3] ACPI 6.2, sec 6.2:
+ OSPM uses device configuration objects to configure hardware resources
+ for devices enumerated via ACPI. Device configuration objects provide
+ information about current and possible resource requirements, the
+ relationship between shared resources, and methods for configuring
+ hardware resources.
+
+ When OSPM enumerates a device, it calls _PRS to determine the resource
+ requirements of the device. It may also call _CRS to find the current
+ resource settings for the device. Using this information, the Plug and
+ Play system determines what resources the device should consume and
+ sets those resources by calling the device’s _SRS control method.
+
+ In ACPI, devices can consume resources (for example, legacy keyboards),
+ provide resources (for example, a proprietary PCI bridge), or do both.
+ Unless otherwise specified, resources for a device are assumed to be
+ taken from the nearest matching resource above the device in the device
+ hierarchy.
+
+[4] ACPI 6.2, sec 6.4.3.5.1, 2, 3, 4:
+ QWord/DWord/Word Address Space Descriptor (.1, .2, .3)
+ General Flags: Bit [0] Ignored
+
+ Extended Address Space Descriptor (.4)
+ General Flags: Bit [0] Consumer/Producer:
+
+ * 1 – This device consumes this resource
+ * 0 – This device produces and consumes this resource
+
+[5] ACPI 6.2, sec 19.6.43:
+ ResourceUsage specifies whether the Memory range is consumed by
+ this device (ResourceConsumer) or passed on to child devices
+ (ResourceProducer). If nothing is specified, then
+ ResourceConsumer is assumed.
+
+[6] PCI Firmware 3.2, sec 4.1.2:
+ If the operating system does not natively comprehend reserving the
+ MMCFG region, the MMCFG region must be reserved by firmware. The
+ address range reported in the MCFG table or by _CBA method (see Section
+ 4.1.3) must be reserved by declaring a motherboard resource. For most
+ systems, the motherboard resource would appear at the root of the ACPI
+ namespace (under \_SB) in a node with a _HID of EISAID (PNP0C02), and
+ the resources in this case should not be claimed in the root PCI bus’s
+ _CRS. The resources can optionally be returned in Int15 E820 or
+ EFIGetMemoryMap as reserved memory but must always be reported through
+ ACPI as a motherboard resource.
+
+[7] PCI Express 4.0, sec 7.2.2:
+ For systems that are PC-compatible, or that do not implement a
+ processor-architecture-specific firmware interface standard that allows
+ access to the Configuration Space, the ECAM is required as defined in
+ this section.
+
+[8] PCI Firmware 3.2, sec 4.1.2:
+ The MCFG table is an ACPI table that is used to communicate the base
+ addresses corresponding to the non-hot removable PCI Segment Groups
+ range within a PCI Segment Group available to the operating system at
+ boot. This is required for the PC-compatible systems.
+
+ The MCFG table is only used to communicate the base addresses
+ corresponding to the PCI Segment Groups available to the system at
+ boot.
+
+[9] PCI Firmware 3.2, sec 4.1.3:
+ The _CBA (Memory mapped Configuration Base Address) control method is
+ an optional ACPI object that returns the 64-bit memory mapped
+ configuration base address for the hot plug capable host bridge. The
+ base address returned by _CBA is processor-relative address. The _CBA
+ control method evaluates to an Integer.
+
+ This control method appears under a host bridge object. When the _CBA
+ method appears under an active host bridge object, the operating system
+ evaluates this structure to identify the memory mapped configuration
+ base address corresponding to the PCI Segment Group for the bus number
+ range specified in _CRS method. An ACPI name space object that contains
+ the _CBA method must also contain a corresponding _SEG method.
diff --git a/Documentation/PCI/boot-interrupts.rst b/Documentation/PCI/boot-interrupts.rst
new file mode 100644
index 000000000..2ec70121b
--- /dev/null
+++ b/Documentation/PCI/boot-interrupts.rst
@@ -0,0 +1,159 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+Boot Interrupts
+===============
+
+:Author: - Sean V Kelley <sean.v.kelley@linux.intel.com>
+
+Overview
+========
+
+On PCI Express, interrupts are represented with either MSI or inbound
+interrupt messages (Assert_INTx/Deassert_INTx). The integrated IO-APIC in a
+given Core IO converts the legacy interrupt messages from PCI Express to
+MSI interrupts. If the IO-APIC is disabled (via the mask bits in the
+IO-APIC table entries), the messages are routed to the legacy PCH. This
+in-band interrupt mechanism was traditionally necessary for systems that
+did not support the IO-APIC and for boot. Intel in the past has used the
+term "boot interrupts" to describe this mechanism. Further, the PCI Express
+protocol describes this in-band legacy wire-interrupt INTx mechanism for
+I/O devices to signal PCI-style level interrupts. The subsequent paragraphs
+describe problems with the Core IO handling of INTx message routing to the
+PCH and mitigation within BIOS and the OS.
+
+
+Issue
+=====
+
+When in-band legacy INTx messages are forwarded to the PCH, they in turn
+trigger a new interrupt for which the OS likely lacks a handler. When an
+interrupt goes unhandled over time, they are tracked by the Linux kernel as
+Spurious Interrupts. The IRQ will be disabled by the Linux kernel after it
+reaches a specific count with the error "nobody cared". This disabled IRQ
+now prevents valid usage by an existing interrupt which may happen to share
+the IRQ line::
+
+ irq 19: nobody cared (try booting with the "irqpoll" option)
+ CPU: 0 PID: 2988 Comm: irq/34-nipalk Tainted: 4.14.87-rt49-02410-g4a640ec-dirty #1
+ Hardware name: National Instruments NI PXIe-8880/NI PXIe-8880, BIOS 2.1.5f1 01/09/2020
+ Call Trace:
+
+ <IRQ>
+ ? dump_stack+0x46/0x5e
+ ? __report_bad_irq+0x2e/0xb0
+ ? note_interrupt+0x242/0x290
+ ? nNIKAL100_memoryRead16+0x8/0x10 [nikal]
+ ? handle_irq_event_percpu+0x55/0x70
+ ? handle_irq_event+0x4f/0x80
+ ? handle_fasteoi_irq+0x81/0x180
+ ? handle_irq+0x1c/0x30
+ ? do_IRQ+0x41/0xd0
+ ? common_interrupt+0x84/0x84
+ </IRQ>
+
+ handlers:
+ irq_default_primary_handler threaded usb_hcd_irq
+ Disabling IRQ #19
+
+
+Conditions
+==========
+
+The use of threaded interrupts is the most likely condition to trigger
+this problem today. Threaded interrupts may not be reenabled after the IRQ
+handler wakes. These "one shot" conditions mean that the threaded interrupt
+needs to keep the interrupt line masked until the threaded handler has run.
+Especially when dealing with high data rate interrupts, the thread needs to
+run to completion; otherwise some handlers will end up in stack overflows
+since the interrupt of the issuing device is still active.
+
+Affected Chipsets
+=================
+
+The legacy interrupt forwarding mechanism exists today in a number of
+devices including but not limited to chipsets from AMD/ATI, Broadcom, and
+Intel. Changes made through the mitigations below have been applied to
+drivers/pci/quirks.c
+
+Starting with ICX there are no longer any IO-APICs in the Core IO's
+devices. IO-APIC is only in the PCH. Devices connected to the Core IO's
+PCIe Root Ports will use native MSI/MSI-X mechanisms.
+
+Mitigations
+===========
+
+The mitigations take the form of PCI quirks. The preference has been to
+first identify and make use of a means to disable the routing to the PCH.
+In such a case a quirk to disable boot interrupt generation can be
+added. [1]_
+
+Intel® 6300ESB I/O Controller Hub
+ Alternate Base Address Register:
+ BIE: Boot Interrupt Enable
+
+ == ===========================
+ 0 Boot interrupt is enabled.
+ 1 Boot interrupt is disabled.
+ == ===========================
+
+Intel® Sandy Bridge through Sky Lake based Xeon servers:
+ Coherent Interface Protocol Interrupt Control
+ dis_intx_route2pch/dis_intx_route2ich/dis_intx_route2dmi2:
+ When this bit is set. Local INTx messages received from the
+ Intel® Quick Data DMA/PCI Express ports are not routed to legacy
+ PCH - they are either converted into MSI via the integrated IO-APIC
+ (if the IO-APIC mask bit is clear in the appropriate entries)
+ or cause no further action (when mask bit is set)
+
+In the absence of a way to directly disable the routing, another approach
+has been to make use of PCI Interrupt pin to INTx routing tables for
+purposes of redirecting the interrupt handler to the rerouted interrupt
+line by default. Therefore, on chipsets where this INTx routing cannot be
+disabled, the Linux kernel will reroute the valid interrupt to its legacy
+interrupt. This redirection of the handler will prevent the occurrence of
+the spurious interrupt detection which would ordinarily disable the IRQ
+line due to excessive unhandled counts. [2]_
+
+The config option X86_REROUTE_FOR_BROKEN_BOOT_IRQS exists to enable (or
+disable) the redirection of the interrupt handler to the PCH interrupt
+line. The option can be overridden by either pci=ioapicreroute or
+pci=noioapicreroute. [3]_
+
+
+More Documentation
+==================
+
+There is an overview of the legacy interrupt handling in several datasheets
+(6300ESB and 6700PXH below). While largely the same, it provides insight
+into the evolution of its handling with chipsets.
+
+Example of disabling of the boot interrupt
+------------------------------------------
+
+ - Intel® 6300ESB I/O Controller Hub (Document # 300641-004US)
+ 5.7.3 Boot Interrupt
+ https://www.intel.com/content/dam/doc/datasheet/6300esb-io-controller-hub-datasheet.pdf
+
+ - Intel® Xeon® Processor E5-1600/2400/2600/4600 v3 Product Families
+ Datasheet - Volume 2: Registers (Document # 330784-003)
+ 6.6.41 cipintrc Coherent Interface Protocol Interrupt Control
+ https://www.intel.com/content/dam/www/public/us/en/documents/datasheets/xeon-e5-v3-datasheet-vol-2.pdf
+
+Example of handler rerouting
+----------------------------
+
+ - Intel® 6700PXH 64-bit PCI Hub (Document # 302628)
+ 2.15.2 PCI Express Legacy INTx Support and Boot Interrupt
+ https://www.intel.com/content/dam/doc/datasheet/6700pxh-64-bit-pci-hub-datasheet.pdf
+
+
+If you have any legacy PCI interrupt questions that aren't answered, email me.
+
+Cheers,
+ Sean V Kelley
+ sean.v.kelley@linux.intel.com
+
+.. [1] https://lore.kernel.org/r/12131949181903-git-send-email-sassmann@suse.de/
+.. [2] https://lore.kernel.org/r/12131949182094-git-send-email-sassmann@suse.de/
+.. [3] https://lore.kernel.org/r/487C8EA7.6020205@suse.de/
diff --git a/Documentation/PCI/endpoint/function/binding/pci-test.rst b/Documentation/PCI/endpoint/function/binding/pci-test.rst
new file mode 100644
index 000000000..57ee866fb
--- /dev/null
+++ b/Documentation/PCI/endpoint/function/binding/pci-test.rst
@@ -0,0 +1,26 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==========================
+PCI Test Endpoint Function
+==========================
+
+name: Should be "pci_epf_test" to bind to the pci_epf_test driver.
+
+Configurable Fields:
+
+================ ===========================================================
+vendorid should be 0x104c
+deviceid should be 0xb500 for DRA74x and 0xb501 for DRA72x
+revid don't care
+progif_code don't care
+subclass_code don't care
+baseclass_code should be 0xff
+cache_line_size don't care
+subsys_vendor_id don't care
+subsys_id don't care
+interrupt_pin Should be 1 - INTA, 2 - INTB, 3 - INTC, 4 -INTD
+msi_interrupts Should be 1 to 32 depending on the number of MSI interrupts
+ to test
+msix_interrupts Should be 1 to 2048 depending on the number of MSI-X
+ interrupts to test
+================ ===========================================================
diff --git a/Documentation/PCI/endpoint/index.rst b/Documentation/PCI/endpoint/index.rst
new file mode 100644
index 000000000..4ca7439fb
--- /dev/null
+++ b/Documentation/PCI/endpoint/index.rst
@@ -0,0 +1,15 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+======================
+PCI Endpoint Framework
+======================
+
+.. toctree::
+ :maxdepth: 2
+
+ pci-endpoint
+ pci-endpoint-cfs
+ pci-test-function
+ pci-test-howto
+
+ function/binding/pci-test
diff --git a/Documentation/PCI/endpoint/pci-endpoint-cfs.rst b/Documentation/PCI/endpoint/pci-endpoint-cfs.rst
new file mode 100644
index 000000000..1bbd81ed0
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-endpoint-cfs.rst
@@ -0,0 +1,118 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================================
+Configuring PCI Endpoint Using CONFIGFS
+=======================================
+
+:Author: Kishon Vijay Abraham I <kishon@ti.com>
+
+The PCI Endpoint Core exposes configfs entry (pci_ep) to configure the
+PCI endpoint function and to bind the endpoint function
+with the endpoint controller. (For introducing other mechanisms to
+configure the PCI Endpoint Function refer to [1]).
+
+Mounting configfs
+=================
+
+The PCI Endpoint Core layer creates pci_ep directory in the mounted configfs
+directory. configfs can be mounted using the following command::
+
+ mount -t configfs none /sys/kernel/config
+
+Directory Structure
+===================
+
+The pci_ep configfs has two directories at its root: controllers and
+functions. Every EPC device present in the system will have an entry in
+the *controllers* directory and every EPF driver present in the system
+will have an entry in the *functions* directory.
+::
+
+ /sys/kernel/config/pci_ep/
+ .. controllers/
+ .. functions/
+
+Creating EPF Device
+===================
+
+Every registered EPF driver will be listed in controllers directory. The
+entries corresponding to EPF driver will be created by the EPF core.
+::
+
+ /sys/kernel/config/pci_ep/functions/
+ .. <EPF Driver1>/
+ ... <EPF Device 11>/
+ ... <EPF Device 21>/
+ .. <EPF Driver2>/
+ ... <EPF Device 12>/
+ ... <EPF Device 22>/
+
+In order to create a <EPF device> of the type probed by <EPF Driver>, the
+user has to create a directory inside <EPF DriverN>.
+
+Every <EPF device> directory consists of the following entries that can be
+used to configure the standard configuration header of the endpoint function.
+(These entries are created by the framework when any new <EPF Device> is
+created)
+::
+
+ .. <EPF Driver1>/
+ ... <EPF Device 11>/
+ ... vendorid
+ ... deviceid
+ ... revid
+ ... progif_code
+ ... subclass_code
+ ... baseclass_code
+ ... cache_line_size
+ ... subsys_vendor_id
+ ... subsys_id
+ ... interrupt_pin
+
+EPC Device
+==========
+
+Every registered EPC device will be listed in controllers directory. The
+entries corresponding to EPC device will be created by the EPC core.
+::
+
+ /sys/kernel/config/pci_ep/controllers/
+ .. <EPC Device1>/
+ ... <Symlink EPF Device11>/
+ ... <Symlink EPF Device12>/
+ ... start
+ .. <EPC Device2>/
+ ... <Symlink EPF Device21>/
+ ... <Symlink EPF Device22>/
+ ... start
+
+The <EPC Device> directory will have a list of symbolic links to
+<EPF Device>. These symbolic links should be created by the user to
+represent the functions present in the endpoint device.
+
+The <EPC Device> directory will also have a *start* field. Once
+"1" is written to this field, the endpoint device will be ready to
+establish the link with the host. This is usually done after
+all the EPF devices are created and linked with the EPC device.
+::
+
+ | controllers/
+ | <Directory: EPC name>/
+ | <Symbolic Link: Function>
+ | start
+ | functions/
+ | <Directory: EPF driver>/
+ | <Directory: EPF device>/
+ | vendorid
+ | deviceid
+ | revid
+ | progif_code
+ | subclass_code
+ | baseclass_code
+ | cache_line_size
+ | subsys_vendor_id
+ | subsys_id
+ | interrupt_pin
+ | function
+
+[1] :doc:`pci-endpoint`
diff --git a/Documentation/PCI/endpoint/pci-endpoint.rst b/Documentation/PCI/endpoint/pci-endpoint.rst
new file mode 100644
index 000000000..4f5622a65
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-endpoint.rst
@@ -0,0 +1,231 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+:Author: Kishon Vijay Abraham I <kishon@ti.com>
+
+This document is a guide to use the PCI Endpoint Framework in order to create
+endpoint controller driver, endpoint function driver, and using configfs
+interface to bind the function driver to the controller driver.
+
+Introduction
+============
+
+Linux has a comprehensive PCI subsystem to support PCI controllers that
+operates in Root Complex mode. The subsystem has capability to scan PCI bus,
+assign memory resources and IRQ resources, load PCI driver (based on
+vendor ID, device ID), support other services like hot-plug, power management,
+advanced error reporting and virtual channels.
+
+However the PCI controller IP integrated in some SoCs is capable of operating
+either in Root Complex mode or Endpoint mode. PCI Endpoint Framework will
+add endpoint mode support in Linux. This will help to run Linux in an
+EP system which can have a wide variety of use cases from testing or
+validation, co-processor accelerator, etc.
+
+PCI Endpoint Core
+=================
+
+The PCI Endpoint Core layer comprises 3 components: the Endpoint Controller
+library, the Endpoint Function library, and the configfs layer to bind the
+endpoint function with the endpoint controller.
+
+PCI Endpoint Controller(EPC) Library
+------------------------------------
+
+The EPC library provides APIs to be used by the controller that can operate
+in endpoint mode. It also provides APIs to be used by function driver/library
+in order to implement a particular endpoint function.
+
+APIs for the PCI controller Driver
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This section lists the APIs that the PCI Endpoint core provides to be used
+by the PCI controller driver.
+
+* devm_pci_epc_create()/pci_epc_create()
+
+ The PCI controller driver should implement the following ops:
+
+ * write_header: ops to populate configuration space header
+ * set_bar: ops to configure the BAR
+ * clear_bar: ops to reset the BAR
+ * alloc_addr_space: ops to allocate in PCI controller address space
+ * free_addr_space: ops to free the allocated address space
+ * raise_irq: ops to raise a legacy, MSI or MSI-X interrupt
+ * start: ops to start the PCI link
+ * stop: ops to stop the PCI link
+
+ The PCI controller driver can then create a new EPC device by invoking
+ devm_pci_epc_create()/pci_epc_create().
+
+* devm_pci_epc_destroy()/pci_epc_destroy()
+
+ The PCI controller driver can destroy the EPC device created by either
+ devm_pci_epc_create() or pci_epc_create() using devm_pci_epc_destroy() or
+ pci_epc_destroy().
+
+* pci_epc_linkup()
+
+ In order to notify all the function devices that the EPC device to which
+ they are linked has established a link with the host, the PCI controller
+ driver should invoke pci_epc_linkup().
+
+* pci_epc_mem_init()
+
+ Initialize the pci_epc_mem structure used for allocating EPC addr space.
+
+* pci_epc_mem_exit()
+
+ Cleanup the pci_epc_mem structure allocated during pci_epc_mem_init().
+
+
+EPC APIs for the PCI Endpoint Function Driver
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This section lists the APIs that the PCI Endpoint core provides to be used
+by the PCI endpoint function driver.
+
+* pci_epc_write_header()
+
+ The PCI endpoint function driver should use pci_epc_write_header() to
+ write the standard configuration header to the endpoint controller.
+
+* pci_epc_set_bar()
+
+ The PCI endpoint function driver should use pci_epc_set_bar() to configure
+ the Base Address Register in order for the host to assign PCI addr space.
+ Register space of the function driver is usually configured
+ using this API.
+
+* pci_epc_clear_bar()
+
+ The PCI endpoint function driver should use pci_epc_clear_bar() to reset
+ the BAR.
+
+* pci_epc_raise_irq()
+
+ The PCI endpoint function driver should use pci_epc_raise_irq() to raise
+ Legacy Interrupt, MSI or MSI-X Interrupt.
+
+* pci_epc_mem_alloc_addr()
+
+ The PCI endpoint function driver should use pci_epc_mem_alloc_addr(), to
+ allocate memory address from EPC addr space which is required to access
+ RC's buffer
+
+* pci_epc_mem_free_addr()
+
+ The PCI endpoint function driver should use pci_epc_mem_free_addr() to
+ free the memory space allocated using pci_epc_mem_alloc_addr().
+
+Other EPC APIs
+~~~~~~~~~~~~~~
+
+There are other APIs provided by the EPC library. These are used for binding
+the EPF device with EPC device. pci-ep-cfs.c can be used as reference for
+using these APIs.
+
+* pci_epc_get()
+
+ Get a reference to the PCI endpoint controller based on the device name of
+ the controller.
+
+* pci_epc_put()
+
+ Release the reference to the PCI endpoint controller obtained using
+ pci_epc_get()
+
+* pci_epc_add_epf()
+
+ Add a PCI endpoint function to a PCI endpoint controller. A PCIe device
+ can have up to 8 functions according to the specification.
+
+* pci_epc_remove_epf()
+
+ Remove the PCI endpoint function from PCI endpoint controller.
+
+* pci_epc_start()
+
+ The PCI endpoint function driver should invoke pci_epc_start() once it
+ has configured the endpoint function and wants to start the PCI link.
+
+* pci_epc_stop()
+
+ The PCI endpoint function driver should invoke pci_epc_stop() to stop
+ the PCI LINK.
+
+
+PCI Endpoint Function(EPF) Library
+----------------------------------
+
+The EPF library provides APIs to be used by the function driver and the EPC
+library to provide endpoint mode functionality.
+
+EPF APIs for the PCI Endpoint Function Driver
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This section lists the APIs that the PCI Endpoint core provides to be used
+by the PCI endpoint function driver.
+
+* pci_epf_register_driver()
+
+ The PCI Endpoint Function driver should implement the following ops:
+ * bind: ops to perform when a EPC device has been bound to EPF device
+ * unbind: ops to perform when a binding has been lost between a EPC
+ device and EPF device
+ * linkup: ops to perform when the EPC device has established a
+ connection with a host system
+
+ The PCI Function driver can then register the PCI EPF driver by using
+ pci_epf_register_driver().
+
+* pci_epf_unregister_driver()
+
+ The PCI Function driver can unregister the PCI EPF driver by using
+ pci_epf_unregister_driver().
+
+* pci_epf_alloc_space()
+
+ The PCI Function driver can allocate space for a particular BAR using
+ pci_epf_alloc_space().
+
+* pci_epf_free_space()
+
+ The PCI Function driver can free the allocated space
+ (using pci_epf_alloc_space) by invoking pci_epf_free_space().
+
+APIs for the PCI Endpoint Controller Library
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This section lists the APIs that the PCI Endpoint core provides to be used
+by the PCI endpoint controller library.
+
+* pci_epf_linkup()
+
+ The PCI endpoint controller library invokes pci_epf_linkup() when the
+ EPC device has established the connection to the host.
+
+Other EPF APIs
+~~~~~~~~~~~~~~
+
+There are other APIs provided by the EPF library. These are used to notify
+the function driver when the EPF device is bound to the EPC device.
+pci-ep-cfs.c can be used as reference for using these APIs.
+
+* pci_epf_create()
+
+ Create a new PCI EPF device by passing the name of the PCI EPF device.
+ This name will be used to bind the EPF device to a EPF driver.
+
+* pci_epf_destroy()
+
+ Destroy the created PCI EPF device.
+
+* pci_epf_bind()
+
+ pci_epf_bind() should be invoked when the EPF device has been bound to
+ a EPC device.
+
+* pci_epf_unbind()
+
+ pci_epf_unbind() should be invoked when the binding between EPC device
+ and EPF device is lost.
diff --git a/Documentation/PCI/endpoint/pci-test-function.rst b/Documentation/PCI/endpoint/pci-test-function.rst
new file mode 100644
index 000000000..3c8521d7a
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-test-function.rst
@@ -0,0 +1,103 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=================
+PCI Test Function
+=================
+
+:Author: Kishon Vijay Abraham I <kishon@ti.com>
+
+Traditionally PCI RC has always been validated by using standard
+PCI cards like ethernet PCI cards or USB PCI cards or SATA PCI cards.
+However with the addition of EP-core in linux kernel, it is possible
+to configure a PCI controller that can operate in EP mode to work as
+a test device.
+
+The PCI endpoint test device is a virtual device (defined in software)
+used to test the endpoint functionality and serve as a sample driver
+for other PCI endpoint devices (to use the EP framework).
+
+The PCI endpoint test device has the following registers:
+
+ 1) PCI_ENDPOINT_TEST_MAGIC
+ 2) PCI_ENDPOINT_TEST_COMMAND
+ 3) PCI_ENDPOINT_TEST_STATUS
+ 4) PCI_ENDPOINT_TEST_SRC_ADDR
+ 5) PCI_ENDPOINT_TEST_DST_ADDR
+ 6) PCI_ENDPOINT_TEST_SIZE
+ 7) PCI_ENDPOINT_TEST_CHECKSUM
+ 8) PCI_ENDPOINT_TEST_IRQ_TYPE
+ 9) PCI_ENDPOINT_TEST_IRQ_NUMBER
+
+* PCI_ENDPOINT_TEST_MAGIC
+
+This register will be used to test BAR0. A known pattern will be written
+and read back from MAGIC register to verify BAR0.
+
+* PCI_ENDPOINT_TEST_COMMAND
+
+This register will be used by the host driver to indicate the function
+that the endpoint device must perform.
+
+======== ================================================================
+Bitfield Description
+======== ================================================================
+Bit 0 raise legacy IRQ
+Bit 1 raise MSI IRQ
+Bit 2 raise MSI-X IRQ
+Bit 3 read command (read data from RC buffer)
+Bit 4 write command (write data to RC buffer)
+Bit 5 copy command (copy data from one RC buffer to another RC buffer)
+======== ================================================================
+
+* PCI_ENDPOINT_TEST_STATUS
+
+This register reflects the status of the PCI endpoint device.
+
+======== ==============================
+Bitfield Description
+======== ==============================
+Bit 0 read success
+Bit 1 read fail
+Bit 2 write success
+Bit 3 write fail
+Bit 4 copy success
+Bit 5 copy fail
+Bit 6 IRQ raised
+Bit 7 source address is invalid
+Bit 8 destination address is invalid
+======== ==============================
+
+* PCI_ENDPOINT_TEST_SRC_ADDR
+
+This register contains the source address (RC buffer address) for the
+COPY/READ command.
+
+* PCI_ENDPOINT_TEST_DST_ADDR
+
+This register contains the destination address (RC buffer address) for
+the COPY/WRITE command.
+
+* PCI_ENDPOINT_TEST_IRQ_TYPE
+
+This register contains the interrupt type (Legacy/MSI) triggered
+for the READ/WRITE/COPY and raise IRQ (Legacy/MSI) commands.
+
+Possible types:
+
+====== ==
+Legacy 0
+MSI 1
+MSI-X 2
+====== ==
+
+* PCI_ENDPOINT_TEST_IRQ_NUMBER
+
+This register contains the triggered ID interrupt.
+
+Admissible values:
+
+====== ===========
+Legacy 0
+MSI [1 .. 32]
+MSI-X [1 .. 2048]
+====== ===========
diff --git a/Documentation/PCI/endpoint/pci-test-howto.rst b/Documentation/PCI/endpoint/pci-test-howto.rst
new file mode 100644
index 000000000..909f770a0
--- /dev/null
+++ b/Documentation/PCI/endpoint/pci-test-howto.rst
@@ -0,0 +1,235 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================
+PCI Test User Guide
+===================
+
+:Author: Kishon Vijay Abraham I <kishon@ti.com>
+
+This document is a guide to help users use pci-epf-test function driver
+and pci_endpoint_test host driver for testing PCI. The list of steps to
+be followed in the host side and EP side is given below.
+
+Endpoint Device
+===============
+
+Endpoint Controller Devices
+---------------------------
+
+To find the list of endpoint controller devices in the system::
+
+ # ls /sys/class/pci_epc/
+ 51000000.pcie_ep
+
+If PCI_ENDPOINT_CONFIGFS is enabled::
+
+ # ls /sys/kernel/config/pci_ep/controllers
+ 51000000.pcie_ep
+
+
+Endpoint Function Drivers
+-------------------------
+
+To find the list of endpoint function drivers in the system::
+
+ # ls /sys/bus/pci-epf/drivers
+ pci_epf_test
+
+If PCI_ENDPOINT_CONFIGFS is enabled::
+
+ # ls /sys/kernel/config/pci_ep/functions
+ pci_epf_test
+
+
+Creating pci-epf-test Device
+----------------------------
+
+PCI endpoint function device can be created using the configfs. To create
+pci-epf-test device, the following commands can be used::
+
+ # mount -t configfs none /sys/kernel/config
+ # cd /sys/kernel/config/pci_ep/
+ # mkdir functions/pci_epf_test/func1
+
+The "mkdir func1" above creates the pci-epf-test function device that will
+be probed by pci_epf_test driver.
+
+The PCI endpoint framework populates the directory with the following
+configurable fields::
+
+ # ls functions/pci_epf_test/func1
+ baseclass_code interrupt_pin progif_code subsys_id
+ cache_line_size msi_interrupts revid subsys_vendorid
+ deviceid msix_interrupts subclass_code vendorid
+
+The PCI endpoint function driver populates these entries with default values
+when the device is bound to the driver. The pci-epf-test driver populates
+vendorid with 0xffff and interrupt_pin with 0x0001::
+
+ # cat functions/pci_epf_test/func1/vendorid
+ 0xffff
+ # cat functions/pci_epf_test/func1/interrupt_pin
+ 0x0001
+
+
+Configuring pci-epf-test Device
+-------------------------------
+
+The user can configure the pci-epf-test device using configfs entry. In order
+to change the vendorid and the number of MSI interrupts used by the function
+device, the following commands can be used::
+
+ # echo 0x104c > functions/pci_epf_test/func1/vendorid
+ # echo 0xb500 > functions/pci_epf_test/func1/deviceid
+ # echo 16 > functions/pci_epf_test/func1/msi_interrupts
+ # echo 8 > functions/pci_epf_test/func1/msix_interrupts
+
+
+Binding pci-epf-test Device to EP Controller
+--------------------------------------------
+
+In order for the endpoint function device to be useful, it has to be bound to
+a PCI endpoint controller driver. Use the configfs to bind the function
+device to one of the controller driver present in the system::
+
+ # ln -s functions/pci_epf_test/func1 controllers/51000000.pcie_ep/
+
+Once the above step is completed, the PCI endpoint is ready to establish a link
+with the host.
+
+
+Start the Link
+--------------
+
+In order for the endpoint device to establish a link with the host, the _start_
+field should be populated with '1'::
+
+ # echo 1 > controllers/51000000.pcie_ep/start
+
+
+RootComplex Device
+==================
+
+lspci Output
+------------
+
+Note that the devices listed here correspond to the value populated in 1.4
+above::
+
+ 00:00.0 PCI bridge: Texas Instruments Device 8888 (rev 01)
+ 01:00.0 Unassigned class [ff00]: Texas Instruments Device b500
+
+
+Using Endpoint Test function Device
+-----------------------------------
+
+pcitest.sh added in tools/pci/ can be used to run all the default PCI endpoint
+tests. To compile this tool the following commands should be used::
+
+ # cd <kernel-dir>
+ # make -C tools/pci
+
+or if you desire to compile and install in your system::
+
+ # cd <kernel-dir>
+ # make -C tools/pci install
+
+The tool and script will be located in <rootfs>/usr/bin/
+
+
+pcitest.sh Output
+~~~~~~~~~~~~~~~~~
+::
+
+ # pcitest.sh
+ BAR tests
+
+ BAR0: OKAY
+ BAR1: OKAY
+ BAR2: OKAY
+ BAR3: OKAY
+ BAR4: NOT OKAY
+ BAR5: NOT OKAY
+
+ Interrupt tests
+
+ SET IRQ TYPE TO LEGACY: OKAY
+ LEGACY IRQ: NOT OKAY
+ SET IRQ TYPE TO MSI: OKAY
+ MSI1: OKAY
+ MSI2: OKAY
+ MSI3: OKAY
+ MSI4: OKAY
+ MSI5: OKAY
+ MSI6: OKAY
+ MSI7: OKAY
+ MSI8: OKAY
+ MSI9: OKAY
+ MSI10: OKAY
+ MSI11: OKAY
+ MSI12: OKAY
+ MSI13: OKAY
+ MSI14: OKAY
+ MSI15: OKAY
+ MSI16: OKAY
+ MSI17: NOT OKAY
+ MSI18: NOT OKAY
+ MSI19: NOT OKAY
+ MSI20: NOT OKAY
+ MSI21: NOT OKAY
+ MSI22: NOT OKAY
+ MSI23: NOT OKAY
+ MSI24: NOT OKAY
+ MSI25: NOT OKAY
+ MSI26: NOT OKAY
+ MSI27: NOT OKAY
+ MSI28: NOT OKAY
+ MSI29: NOT OKAY
+ MSI30: NOT OKAY
+ MSI31: NOT OKAY
+ MSI32: NOT OKAY
+ SET IRQ TYPE TO MSI-X: OKAY
+ MSI-X1: OKAY
+ MSI-X2: OKAY
+ MSI-X3: OKAY
+ MSI-X4: OKAY
+ MSI-X5: OKAY
+ MSI-X6: OKAY
+ MSI-X7: OKAY
+ MSI-X8: OKAY
+ MSI-X9: NOT OKAY
+ MSI-X10: NOT OKAY
+ MSI-X11: NOT OKAY
+ MSI-X12: NOT OKAY
+ MSI-X13: NOT OKAY
+ MSI-X14: NOT OKAY
+ MSI-X15: NOT OKAY
+ MSI-X16: NOT OKAY
+ [...]
+ MSI-X2047: NOT OKAY
+ MSI-X2048: NOT OKAY
+
+ Read Tests
+
+ SET IRQ TYPE TO MSI: OKAY
+ READ ( 1 bytes): OKAY
+ READ ( 1024 bytes): OKAY
+ READ ( 1025 bytes): OKAY
+ READ (1024000 bytes): OKAY
+ READ (1024001 bytes): OKAY
+
+ Write Tests
+
+ WRITE ( 1 bytes): OKAY
+ WRITE ( 1024 bytes): OKAY
+ WRITE ( 1025 bytes): OKAY
+ WRITE (1024000 bytes): OKAY
+ WRITE (1024001 bytes): OKAY
+
+ Copy Tests
+
+ COPY ( 1 bytes): OKAY
+ COPY ( 1024 bytes): OKAY
+ COPY ( 1025 bytes): OKAY
+ COPY (1024000 bytes): OKAY
+ COPY (1024001 bytes): OKAY
diff --git a/Documentation/PCI/index.rst b/Documentation/PCI/index.rst
new file mode 100644
index 000000000..c17c87af1
--- /dev/null
+++ b/Documentation/PCI/index.rst
@@ -0,0 +1,20 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+=======================
+Linux PCI Bus Subsystem
+=======================
+
+.. toctree::
+ :maxdepth: 2
+ :numbered:
+
+ pci
+ pciebus-howto
+ pci-iov-howto
+ msi-howto
+ sysfs-pci
+ acpi-info
+ pci-error-recovery
+ pcieaer-howto
+ endpoint/index
+ boot-interrupts
diff --git a/Documentation/PCI/msi-howto.rst b/Documentation/PCI/msi-howto.rst
new file mode 100644
index 000000000..aa2046af6
--- /dev/null
+++ b/Documentation/PCI/msi-howto.rst
@@ -0,0 +1,287 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+==========================
+The MSI Driver Guide HOWTO
+==========================
+
+:Authors: Tom L Nguyen; Martine Silbermann; Matthew Wilcox
+
+:Copyright: 2003, 2008 Intel Corporation
+
+About this guide
+================
+
+This guide describes the basics of Message Signaled Interrupts (MSIs),
+the advantages of using MSI over traditional interrupt mechanisms, how
+to change your driver to use MSI or MSI-X and some basic diagnostics to
+try if a device doesn't support MSIs.
+
+
+What are MSIs?
+==============
+
+A Message Signaled Interrupt is a write from the device to a special
+address which causes an interrupt to be received by the CPU.
+
+The MSI capability was first specified in PCI 2.2 and was later enhanced
+in PCI 3.0 to allow each interrupt to be masked individually. The MSI-X
+capability was also introduced with PCI 3.0. It supports more interrupts
+per device than MSI and allows interrupts to be independently configured.
+
+Devices may support both MSI and MSI-X, but only one can be enabled at
+a time.
+
+
+Why use MSIs?
+=============
+
+There are three reasons why using MSIs can give an advantage over
+traditional pin-based interrupts.
+
+Pin-based PCI interrupts are often shared amongst several devices.
+To support this, the kernel must call each interrupt handler associated
+with an interrupt, which leads to reduced performance for the system as
+a whole. MSIs are never shared, so this problem cannot arise.
+
+When a device writes data to memory, then raises a pin-based interrupt,
+it is possible that the interrupt may arrive before all the data has
+arrived in memory (this becomes more likely with devices behind PCI-PCI
+bridges). In order to ensure that all the data has arrived in memory,
+the interrupt handler must read a register on the device which raised
+the interrupt. PCI transaction ordering rules require that all the data
+arrive in memory before the value may be returned from the register.
+Using MSIs avoids this problem as the interrupt-generating write cannot
+pass the data writes, so by the time the interrupt is raised, the driver
+knows that all the data has arrived in memory.
+
+PCI devices can only support a single pin-based interrupt per function.
+Often drivers have to query the device to find out what event has
+occurred, slowing down interrupt handling for the common case. With
+MSIs, a device can support more interrupts, allowing each interrupt
+to be specialised to a different purpose. One possible design gives
+infrequent conditions (such as errors) their own interrupt which allows
+the driver to handle the normal interrupt handling path more efficiently.
+Other possible designs include giving one interrupt to each packet queue
+in a network card or each port in a storage controller.
+
+
+How to use MSIs
+===============
+
+PCI devices are initialised to use pin-based interrupts. The device
+driver has to set up the device to use MSI or MSI-X. Not all machines
+support MSIs correctly, and for those machines, the APIs described below
+will simply fail and the device will continue to use pin-based interrupts.
+
+Include kernel support for MSIs
+-------------------------------
+
+To support MSI or MSI-X, the kernel must be built with the CONFIG_PCI_MSI
+option enabled. This option is only available on some architectures,
+and it may depend on some other options also being set. For example,
+on x86, you must also enable X86_UP_APIC or SMP in order to see the
+CONFIG_PCI_MSI option.
+
+Using MSI
+---------
+
+Most of the hard work is done for the driver in the PCI layer. The driver
+simply has to request that the PCI layer set up the MSI capability for this
+device.
+
+To automatically use MSI or MSI-X interrupt vectors, use the following
+function::
+
+ int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
+ unsigned int max_vecs, unsigned int flags);
+
+which allocates up to max_vecs interrupt vectors for a PCI device. It
+returns the number of vectors allocated or a negative error. If the device
+has a requirements for a minimum number of vectors the driver can pass a
+min_vecs argument set to this limit, and the PCI core will return -ENOSPC
+if it can't meet the minimum number of vectors.
+
+The flags argument is used to specify which type of interrupt can be used
+by the device and the driver (PCI_IRQ_LEGACY, PCI_IRQ_MSI, PCI_IRQ_MSIX).
+A convenient short-hand (PCI_IRQ_ALL_TYPES) is also available to ask for
+any possible kind of interrupt. If the PCI_IRQ_AFFINITY flag is set,
+pci_alloc_irq_vectors() will spread the interrupts around the available CPUs.
+
+To get the Linux IRQ numbers passed to request_irq() and free_irq() and the
+vectors, use the following function::
+
+ int pci_irq_vector(struct pci_dev *dev, unsigned int nr);
+
+Any allocated resources should be freed before removing the device using
+the following function::
+
+ void pci_free_irq_vectors(struct pci_dev *dev);
+
+If a device supports both MSI-X and MSI capabilities, this API will use the
+MSI-X facilities in preference to the MSI facilities. MSI-X supports any
+number of interrupts between 1 and 2048. In contrast, MSI is restricted to
+a maximum of 32 interrupts (and must be a power of two). In addition, the
+MSI interrupt vectors must be allocated consecutively, so the system might
+not be able to allocate as many vectors for MSI as it could for MSI-X. On
+some platforms, MSI interrupts must all be targeted at the same set of CPUs
+whereas MSI-X interrupts can all be targeted at different CPUs.
+
+If a device supports neither MSI-X or MSI it will fall back to a single
+legacy IRQ vector.
+
+The typical usage of MSI or MSI-X interrupts is to allocate as many vectors
+as possible, likely up to the limit supported by the device. If nvec is
+larger than the number supported by the device it will automatically be
+capped to the supported limit, so there is no need to query the number of
+vectors supported beforehand::
+
+ nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_ALL_TYPES)
+ if (nvec < 0)
+ goto out_err;
+
+If a driver is unable or unwilling to deal with a variable number of MSI
+interrupts it can request a particular number of interrupts by passing that
+number to pci_alloc_irq_vectors() function as both 'min_vecs' and
+'max_vecs' parameters::
+
+ ret = pci_alloc_irq_vectors(pdev, nvec, nvec, PCI_IRQ_ALL_TYPES);
+ if (ret < 0)
+ goto out_err;
+
+The most notorious example of the request type described above is enabling
+the single MSI mode for a device. It could be done by passing two 1s as
+'min_vecs' and 'max_vecs'::
+
+ ret = pci_alloc_irq_vectors(pdev, 1, 1, PCI_IRQ_ALL_TYPES);
+ if (ret < 0)
+ goto out_err;
+
+Some devices might not support using legacy line interrupts, in which case
+the driver can specify that only MSI or MSI-X is acceptable::
+
+ nvec = pci_alloc_irq_vectors(pdev, 1, nvec, PCI_IRQ_MSI | PCI_IRQ_MSIX);
+ if (nvec < 0)
+ goto out_err;
+
+Legacy APIs
+-----------
+
+The following old APIs to enable and disable MSI or MSI-X interrupts should
+not be used in new code::
+
+ pci_enable_msi() /* deprecated */
+ pci_disable_msi() /* deprecated */
+ pci_enable_msix_range() /* deprecated */
+ pci_enable_msix_exact() /* deprecated */
+ pci_disable_msix() /* deprecated */
+
+Additionally there are APIs to provide the number of supported MSI or MSI-X
+vectors: pci_msi_vec_count() and pci_msix_vec_count(). In general these
+should be avoided in favor of letting pci_alloc_irq_vectors() cap the
+number of vectors. If you have a legitimate special use case for the count
+of vectors we might have to revisit that decision and add a
+pci_nr_irq_vectors() helper that handles MSI and MSI-X transparently.
+
+Considerations when using MSIs
+------------------------------
+
+Spinlocks
+~~~~~~~~~
+
+Most device drivers have a per-device spinlock which is taken in the
+interrupt handler. With pin-based interrupts or a single MSI, it is not
+necessary to disable interrupts (Linux guarantees the same interrupt will
+not be re-entered). If a device uses multiple interrupts, the driver
+must disable interrupts while the lock is held. If the device sends
+a different interrupt, the driver will deadlock trying to recursively
+acquire the spinlock. Such deadlocks can be avoided by using
+spin_lock_irqsave() or spin_lock_irq() which disable local interrupts
+and acquire the lock (see Documentation/kernel-hacking/locking.rst).
+
+How to tell whether MSI/MSI-X is enabled on a device
+----------------------------------------------------
+
+Using 'lspci -v' (as root) may show some devices with "MSI", "Message
+Signalled Interrupts" or "MSI-X" capabilities. Each of these capabilities
+has an 'Enable' flag which is followed with either "+" (enabled)
+or "-" (disabled).
+
+
+MSI quirks
+==========
+
+Several PCI chipsets or devices are known not to support MSIs.
+The PCI stack provides three ways to disable MSIs:
+
+1. globally
+2. on all devices behind a specific bridge
+3. on a single device
+
+Disabling MSIs globally
+-----------------------
+
+Some host chipsets simply don't support MSIs properly. If we're
+lucky, the manufacturer knows this and has indicated it in the ACPI
+FADT table. In this case, Linux automatically disables MSIs.
+Some boards don't include this information in the table and so we have
+to detect them ourselves. The complete list of these is found near the
+quirk_disable_all_msi() function in drivers/pci/quirks.c.
+
+If you have a board which has problems with MSIs, you can pass pci=nomsi
+on the kernel command line to disable MSIs on all devices. It would be
+in your best interests to report the problem to linux-pci@vger.kernel.org
+including a full 'lspci -v' so we can add the quirks to the kernel.
+
+Disabling MSIs below a bridge
+-----------------------------
+
+Some PCI bridges are not able to route MSIs between busses properly.
+In this case, MSIs must be disabled on all devices behind the bridge.
+
+Some bridges allow you to enable MSIs by changing some bits in their
+PCI configuration space (especially the Hypertransport chipsets such
+as the nVidia nForce and Serverworks HT2000). As with host chipsets,
+Linux mostly knows about them and automatically enables MSIs if it can.
+If you have a bridge unknown to Linux, you can enable
+MSIs in configuration space using whatever method you know works, then
+enable MSIs on that bridge by doing::
+
+ echo 1 > /sys/bus/pci/devices/$bridge/msi_bus
+
+where $bridge is the PCI address of the bridge you've enabled (eg
+0000:00:0e.0).
+
+To disable MSIs, echo 0 instead of 1. Changing this value should be
+done with caution as it could break interrupt handling for all devices
+below this bridge.
+
+Again, please notify linux-pci@vger.kernel.org of any bridges that need
+special handling.
+
+Disabling MSIs on a single device
+---------------------------------
+
+Some devices are known to have faulty MSI implementations. Usually this
+is handled in the individual device driver, but occasionally it's necessary
+to handle this with a quirk. Some drivers have an option to disable use
+of MSI. While this is a convenient workaround for the driver author,
+it is not good practice, and should not be emulated.
+
+Finding why MSIs are disabled on a device
+-----------------------------------------
+
+From the above three sections, you can see that there are many reasons
+why MSIs may not be enabled for a given device. Your first step should
+be to examine your dmesg carefully to determine whether MSIs are enabled
+for your machine. You should also check your .config to be sure you
+have enabled CONFIG_PCI_MSI.
+
+Then, 'lspci -t' gives the list of bridges above a device. Reading
+`/sys/bus/pci/devices/*/msi_bus` will tell you whether MSIs are enabled (1)
+or disabled (0). If 0 is found in any of the msi_bus files belonging
+to bridges between the PCI root and the device, MSIs are disabled.
+
+It is also worth checking the device driver to see whether it supports MSIs.
+For example, it may contain calls to pci_alloc_irq_vectors() with the
+PCI_IRQ_MSI or PCI_IRQ_MSIX flags.
diff --git a/Documentation/PCI/pci-error-recovery.rst b/Documentation/PCI/pci-error-recovery.rst
new file mode 100644
index 000000000..84ceebb08
--- /dev/null
+++ b/Documentation/PCI/pci-error-recovery.rst
@@ -0,0 +1,426 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
+PCI Error Recovery
+==================
+
+
+:Authors: - Linas Vepstas <linasvepstas@gmail.com>
+ - Richard Lary <rlary@us.ibm.com>
+ - Mike Mason <mmlnx@us.ibm.com>
+
+
+Many PCI bus controllers are able to detect a variety of hardware
+PCI errors on the bus, such as parity errors on the data and address
+buses, as well as SERR and PERR errors. Some of the more advanced
+chipsets are able to deal with these errors; these include PCI-E chipsets,
+and the PCI-host bridges found on IBM Power4, Power5 and Power6-based
+pSeries boxes. A typical action taken is to disconnect the affected device,
+halting all I/O to it. The goal of a disconnection is to avoid system
+corruption; for example, to halt system memory corruption due to DMA's
+to "wild" addresses. Typically, a reconnection mechanism is also
+offered, so that the affected PCI device(s) are reset and put back
+into working condition. The reset phase requires coordination
+between the affected device drivers and the PCI controller chip.
+This document describes a generic API for notifying device drivers
+of a bus disconnection, and then performing error recovery.
+This API is currently implemented in the 2.6.16 and later kernels.
+
+Reporting and recovery is performed in several steps. First, when
+a PCI hardware error has resulted in a bus disconnect, that event
+is reported as soon as possible to all affected device drivers,
+including multiple instances of a device driver on multi-function
+cards. This allows device drivers to avoid deadlocking in spinloops,
+waiting for some i/o-space register to change, when it never will.
+It also gives the drivers a chance to defer incoming I/O as
+needed.
+
+Next, recovery is performed in several stages. Most of the complexity
+is forced by the need to handle multi-function devices, that is,
+devices that have multiple device drivers associated with them.
+In the first stage, each driver is allowed to indicate what type
+of reset it desires, the choices being a simple re-enabling of I/O
+or requesting a slot reset.
+
+If any driver requests a slot reset, that is what will be done.
+
+After a reset and/or a re-enabling of I/O, all drivers are
+again notified, so that they may then perform any device setup/config
+that may be required. After these have all completed, a final
+"resume normal operations" event is sent out.
+
+The biggest reason for choosing a kernel-based implementation rather
+than a user-space implementation was the need to deal with bus
+disconnects of PCI devices attached to storage media, and, in particular,
+disconnects from devices holding the root file system. If the root
+file system is disconnected, a user-space mechanism would have to go
+through a large number of contortions to complete recovery. Almost all
+of the current Linux file systems are not tolerant of disconnection
+from/reconnection to their underlying block device. By contrast,
+bus errors are easy to manage in the device driver. Indeed, most
+device drivers already handle very similar recovery procedures;
+for example, the SCSI-generic layer already provides significant
+mechanisms for dealing with SCSI bus errors and SCSI bus resets.
+
+
+Detailed Design
+===============
+
+Design and implementation details below, based on a chain of
+public email discussions with Ben Herrenschmidt, circa 5 April 2005.
+
+The error recovery API support is exposed to the driver in the form of
+a structure of function pointers pointed to by a new field in struct
+pci_driver. A driver that fails to provide the structure is "non-aware",
+and the actual recovery steps taken are platform dependent. The
+arch/powerpc implementation will simulate a PCI hotplug remove/add.
+
+This structure has the form::
+
+ struct pci_error_handlers
+ {
+ int (*error_detected)(struct pci_dev *dev, pci_channel_state_t);
+ int (*mmio_enabled)(struct pci_dev *dev);
+ int (*slot_reset)(struct pci_dev *dev);
+ void (*resume)(struct pci_dev *dev);
+ };
+
+The possible channel states are::
+
+ typedef enum {
+ pci_channel_io_normal, /* I/O channel is in normal state */
+ pci_channel_io_frozen, /* I/O to channel is blocked */
+ pci_channel_io_perm_failure, /* PCI card is dead */
+ } pci_channel_state_t;
+
+Possible return values are::
+
+ enum pci_ers_result {
+ PCI_ERS_RESULT_NONE, /* no result/none/not supported in device driver */
+ PCI_ERS_RESULT_CAN_RECOVER, /* Device driver can recover without slot reset */
+ PCI_ERS_RESULT_NEED_RESET, /* Device driver wants slot to be reset. */
+ PCI_ERS_RESULT_DISCONNECT, /* Device has completely failed, is unrecoverable */
+ PCI_ERS_RESULT_RECOVERED, /* Device driver is fully recovered and operational */
+ };
+
+A driver does not have to implement all of these callbacks; however,
+if it implements any, it must implement error_detected(). If a callback
+is not implemented, the corresponding feature is considered unsupported.
+For example, if mmio_enabled() and resume() aren't there, then it
+is assumed that the driver is not doing any direct recovery and requires
+a slot reset. Typically a driver will want to know about
+a slot_reset().
+
+The actual steps taken by a platform to recover from a PCI error
+event will be platform-dependent, but will follow the general
+sequence described below.
+
+STEP 0: Error Event
+-------------------
+A PCI bus error is detected by the PCI hardware. On powerpc, the slot
+is isolated, in that all I/O is blocked: all reads return 0xffffffff,
+all writes are ignored.
+
+
+STEP 1: Notification
+--------------------
+Platform calls the error_detected() callback on every instance of
+every driver affected by the error.
+
+At this point, the device might not be accessible anymore, depending on
+the platform (the slot will be isolated on powerpc). The driver may
+already have "noticed" the error because of a failing I/O, but this
+is the proper "synchronization point", that is, it gives the driver
+a chance to cleanup, waiting for pending stuff (timers, whatever, etc...)
+to complete; it can take semaphores, schedule, etc... everything but
+touch the device. Within this function and after it returns, the driver
+shouldn't do any new IOs. Called in task context. This is sort of a
+"quiesce" point. See note about interrupts at the end of this doc.
+
+All drivers participating in this system must implement this call.
+The driver must return one of the following result codes:
+
+ - PCI_ERS_RESULT_CAN_RECOVER
+ Driver returns this if it thinks it might be able to recover
+ the HW by just banging IOs or if it wants to be given
+ a chance to extract some diagnostic information (see
+ mmio_enable, below).
+ - PCI_ERS_RESULT_NEED_RESET
+ Driver returns this if it can't recover without a
+ slot reset.
+ - PCI_ERS_RESULT_DISCONNECT
+ Driver returns this if it doesn't want to recover at all.
+
+The next step taken will depend on the result codes returned by the
+drivers.
+
+If all drivers on the segment/slot return PCI_ERS_RESULT_CAN_RECOVER,
+then the platform should re-enable IOs on the slot (or do nothing in
+particular, if the platform doesn't isolate slots), and recovery
+proceeds to STEP 2 (MMIO Enable).
+
+If any driver requested a slot reset (by returning PCI_ERS_RESULT_NEED_RESET),
+then recovery proceeds to STEP 4 (Slot Reset).
+
+If the platform is unable to recover the slot, the next step
+is STEP 6 (Permanent Failure).
+
+.. note::
+
+ The current powerpc implementation assumes that a device driver will
+ *not* schedule or semaphore in this routine; the current powerpc
+ implementation uses one kernel thread to notify all devices;
+ thus, if one device sleeps/schedules, all devices are affected.
+ Doing better requires complex multi-threaded logic in the error
+ recovery implementation (e.g. waiting for all notification threads
+ to "join" before proceeding with recovery.) This seems excessively
+ complex and not worth implementing.
+
+ The current powerpc implementation doesn't much care if the device
+ attempts I/O at this point, or not. I/O's will fail, returning
+ a value of 0xff on read, and writes will be dropped. If more than
+ EEH_MAX_FAILS I/O's are attempted to a frozen adapter, EEH
+ assumes that the device driver has gone into an infinite loop
+ and prints an error to syslog. A reboot is then required to
+ get the device working again.
+
+STEP 2: MMIO Enabled
+--------------------
+The platform re-enables MMIO to the device (but typically not the
+DMA), and then calls the mmio_enabled() callback on all affected
+device drivers.
+
+This is the "early recovery" call. IOs are allowed again, but DMA is
+not, with some restrictions. This is NOT a callback for the driver to
+start operations again, only to peek/poke at the device, extract diagnostic
+information, if any, and eventually do things like trigger a device local
+reset or some such, but not restart operations. This callback is made if
+all drivers on a segment agree that they can try to recover and if no automatic
+link reset was performed by the HW. If the platform can't just re-enable IOs
+without a slot reset or a link reset, it will not call this callback, and
+instead will have gone directly to STEP 3 (Link Reset) or STEP 4 (Slot Reset)
+
+.. note::
+
+ The following is proposed; no platform implements this yet:
+ Proposal: All I/O's should be done _synchronously_ from within
+ this callback, errors triggered by them will be returned via
+ the normal pci_check_whatever() API, no new error_detected()
+ callback will be issued due to an error happening here. However,
+ such an error might cause IOs to be re-blocked for the whole
+ segment, and thus invalidate the recovery that other devices
+ on the same segment might have done, forcing the whole segment
+ into one of the next states, that is, link reset or slot reset.
+
+The driver should return one of the following result codes:
+ - PCI_ERS_RESULT_RECOVERED
+ Driver returns this if it thinks the device is fully
+ functional and thinks it is ready to start
+ normal driver operations again. There is no
+ guarantee that the driver will actually be
+ allowed to proceed, as another driver on the
+ same segment might have failed and thus triggered a
+ slot reset on platforms that support it.
+
+ - PCI_ERS_RESULT_NEED_RESET
+ Driver returns this if it thinks the device is not
+ recoverable in its current state and it needs a slot
+ reset to proceed.
+
+ - PCI_ERS_RESULT_DISCONNECT
+ Same as above. Total failure, no recovery even after
+ reset driver dead. (To be defined more precisely)
+
+The next step taken depends on the results returned by the drivers.
+If all drivers returned PCI_ERS_RESULT_RECOVERED, then the platform
+proceeds to either STEP3 (Link Reset) or to STEP 5 (Resume Operations).
+
+If any driver returned PCI_ERS_RESULT_NEED_RESET, then the platform
+proceeds to STEP 4 (Slot Reset)
+
+STEP 3: Link Reset
+------------------
+The platform resets the link. This is a PCI-Express specific step
+and is done whenever a fatal error has been detected that can be
+"solved" by resetting the link.
+
+STEP 4: Slot Reset
+------------------
+
+In response to a return value of PCI_ERS_RESULT_NEED_RESET, the
+platform will perform a slot reset on the requesting PCI device(s).
+The actual steps taken by a platform to perform a slot reset
+will be platform-dependent. Upon completion of slot reset, the
+platform will call the device slot_reset() callback.
+
+Powerpc platforms implement two levels of slot reset:
+soft reset(default) and fundamental(optional) reset.
+
+Powerpc soft reset consists of asserting the adapter #RST line and then
+restoring the PCI BAR's and PCI configuration header to a state
+that is equivalent to what it would be after a fresh system
+power-on followed by power-on BIOS/system firmware initialization.
+Soft reset is also known as hot-reset.
+
+Powerpc fundamental reset is supported by PCI Express cards only
+and results in device's state machines, hardware logic, port states and
+configuration registers to initialize to their default conditions.
+
+For most PCI devices, a soft reset will be sufficient for recovery.
+Optional fundamental reset is provided to support a limited number
+of PCI Express devices for which a soft reset is not sufficient
+for recovery.
+
+If the platform supports PCI hotplug, then the reset might be
+performed by toggling the slot electrical power off/on.
+
+It is important for the platform to restore the PCI config space
+to the "fresh poweron" state, rather than the "last state". After
+a slot reset, the device driver will almost always use its standard
+device initialization routines, and an unusual config space setup
+may result in hung devices, kernel panics, or silent data corruption.
+
+This call gives drivers the chance to re-initialize the hardware
+(re-download firmware, etc.). At this point, the driver may assume
+that the card is in a fresh state and is fully functional. The slot
+is unfrozen and the driver has full access to PCI config space,
+memory mapped I/O space and DMA. Interrupts (Legacy, MSI, or MSI-X)
+will also be available.
+
+Drivers should not restart normal I/O processing operations
+at this point. If all device drivers report success on this
+callback, the platform will call resume() to complete the sequence,
+and let the driver restart normal I/O processing.
+
+A driver can still return a critical failure for this function if
+it can't get the device operational after reset. If the platform
+previously tried a soft reset, it might now try a hard reset (power
+cycle) and then call slot_reset() again. It the device still can't
+be recovered, there is nothing more that can be done; the platform
+will typically report a "permanent failure" in such a case. The
+device will be considered "dead" in this case.
+
+Drivers for multi-function cards will need to coordinate among
+themselves as to which driver instance will perform any "one-shot"
+or global device initialization. For example, the Symbios sym53cxx2
+driver performs device init only from PCI function 0::
+
+ + if (PCI_FUNC(pdev->devfn) == 0)
+ + sym_reset_scsi_bus(np, 0);
+
+Result codes:
+ - PCI_ERS_RESULT_DISCONNECT
+ Same as above.
+
+Drivers for PCI Express cards that require a fundamental reset must
+set the needs_freset bit in the pci_dev structure in their probe function.
+For example, the QLogic qla2xxx driver sets the needs_freset bit for certain
+PCI card types::
+
+ + /* Set EEH reset type to fundamental if required by hba */
+ + if (IS_QLA24XX(ha) || IS_QLA25XX(ha) || IS_QLA81XX(ha))
+ + pdev->needs_freset = 1;
+ +
+
+Platform proceeds either to STEP 5 (Resume Operations) or STEP 6 (Permanent
+Failure).
+
+.. note::
+
+ The current powerpc implementation does not try a power-cycle
+ reset if the driver returned PCI_ERS_RESULT_DISCONNECT.
+ However, it probably should.
+
+
+STEP 5: Resume Operations
+-------------------------
+The platform will call the resume() callback on all affected device
+drivers if all drivers on the segment have returned
+PCI_ERS_RESULT_RECOVERED from one of the 3 previous callbacks.
+The goal of this callback is to tell the driver to restart activity,
+that everything is back and running. This callback does not return
+a result code.
+
+At this point, if a new error happens, the platform will restart
+a new error recovery sequence.
+
+STEP 6: Permanent Failure
+-------------------------
+A "permanent failure" has occurred, and the platform cannot recover
+the device. The platform will call error_detected() with a
+pci_channel_state_t value of pci_channel_io_perm_failure.
+
+The device driver should, at this point, assume the worst. It should
+cancel all pending I/O, refuse all new I/O, returning -EIO to
+higher layers. The device driver should then clean up all of its
+memory and remove itself from kernel operations, much as it would
+during system shutdown.
+
+The platform will typically notify the system operator of the
+permanent failure in some way. If the device is hotplug-capable,
+the operator will probably want to remove and replace the device.
+Note, however, not all failures are truly "permanent". Some are
+caused by over-heating, some by a poorly seated card. Many
+PCI error events are caused by software bugs, e.g. DMA's to
+wild addresses or bogus split transactions due to programming
+errors. See the discussion in powerpc/eeh-pci-error-recovery.txt
+for additional detail on real-life experience of the causes of
+software errors.
+
+
+Conclusion; General Remarks
+---------------------------
+The way the callbacks are called is platform policy. A platform with
+no slot reset capability may want to just "ignore" drivers that can't
+recover (disconnect them) and try to let other cards on the same segment
+recover. Keep in mind that in most real life cases, though, there will
+be only one driver per segment.
+
+Now, a note about interrupts. If you get an interrupt and your
+device is dead or has been isolated, there is a problem :)
+The current policy is to turn this into a platform policy.
+That is, the recovery API only requires that:
+
+ - There is no guarantee that interrupt delivery can proceed from any
+ device on the segment starting from the error detection and until the
+ slot_reset callback is called, at which point interrupts are expected
+ to be fully operational.
+
+ - There is no guarantee that interrupt delivery is stopped, that is,
+ a driver that gets an interrupt after detecting an error, or that detects
+ an error within the interrupt handler such that it prevents proper
+ ack'ing of the interrupt (and thus removal of the source) should just
+ return IRQ_NOTHANDLED. It's up to the platform to deal with that
+ condition, typically by masking the IRQ source during the duration of
+ the error handling. It is expected that the platform "knows" which
+ interrupts are routed to error-management capable slots and can deal
+ with temporarily disabling that IRQ number during error processing (this
+ isn't terribly complex). That means some IRQ latency for other devices
+ sharing the interrupt, but there is simply no other way. High end
+ platforms aren't supposed to share interrupts between many devices
+ anyway :)
+
+.. note::
+
+ Implementation details for the powerpc platform are discussed in
+ the file Documentation/powerpc/eeh-pci-error-recovery.rst
+
+ As of this writing, there is a growing list of device drivers with
+ patches implementing error recovery. Not all of these patches are in
+ mainline yet. These may be used as "examples":
+
+ - drivers/scsi/ipr
+ - drivers/scsi/sym53c8xx_2
+ - drivers/scsi/qla2xxx
+ - drivers/scsi/lpfc
+ - drivers/next/bnx2.c
+ - drivers/next/e100.c
+ - drivers/net/e1000
+ - drivers/net/e1000e
+ - drivers/net/ixgb
+ - drivers/net/ixgbe
+ - drivers/net/cxgb3
+ - drivers/net/s2io.c
+
+The End
+-------
diff --git a/Documentation/PCI/pci-iov-howto.rst b/Documentation/PCI/pci-iov-howto.rst
new file mode 100644
index 000000000..b9fd00320
--- /dev/null
+++ b/Documentation/PCI/pci-iov-howto.rst
@@ -0,0 +1,172 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+====================================
+PCI Express I/O Virtualization Howto
+====================================
+
+:Copyright: |copy| 2009 Intel Corporation
+:Authors: - Yu Zhao <yu.zhao@intel.com>
+ - Donald Dutile <ddutile@redhat.com>
+
+Overview
+========
+
+What is SR-IOV
+--------------
+
+Single Root I/O Virtualization (SR-IOV) is a PCI Express Extended
+capability which makes one physical device appear as multiple virtual
+devices. The physical device is referred to as Physical Function (PF)
+while the virtual devices are referred to as Virtual Functions (VF).
+Allocation of the VF can be dynamically controlled by the PF via
+registers encapsulated in the capability. By default, this feature is
+not enabled and the PF behaves as traditional PCIe device. Once it's
+turned on, each VF's PCI configuration space can be accessed by its own
+Bus, Device and Function Number (Routing ID). And each VF also has PCI
+Memory Space, which is used to map its register set. VF device driver
+operates on the register set so it can be functional and appear as a
+real existing PCI device.
+
+User Guide
+==========
+
+How can I enable SR-IOV capability
+----------------------------------
+
+Multiple methods are available for SR-IOV enablement.
+In the first method, the device driver (PF driver) will control the
+enabling and disabling of the capability via API provided by SR-IOV core.
+If the hardware has SR-IOV capability, loading its PF driver would
+enable it and all VFs associated with the PF. Some PF drivers require
+a module parameter to be set to determine the number of VFs to enable.
+In the second method, a write to the sysfs file sriov_numvfs will
+enable and disable the VFs associated with a PCIe PF. This method
+enables per-PF, VF enable/disable values versus the first method,
+which applies to all PFs of the same device. Additionally, the
+PCI SRIOV core support ensures that enable/disable operations are
+valid to reduce duplication in multiple drivers for the same
+checks, e.g., check numvfs == 0 if enabling VFs, ensure
+numvfs <= totalvfs.
+The second method is the recommended method for new/future VF devices.
+
+How can I use the Virtual Functions
+-----------------------------------
+
+The VF is treated as hot-plugged PCI devices in the kernel, so they
+should be able to work in the same way as real PCI devices. The VF
+requires device driver that is same as a normal PCI device's.
+
+Developer Guide
+===============
+
+SR-IOV API
+----------
+
+To enable SR-IOV capability:
+
+(a) For the first method, in the driver::
+
+ int pci_enable_sriov(struct pci_dev *dev, int nr_virtfn);
+
+'nr_virtfn' is number of VFs to be enabled.
+
+(b) For the second method, from sysfs::
+
+ echo 'nr_virtfn' > \
+ /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
+
+To disable SR-IOV capability:
+
+(a) For the first method, in the driver::
+
+ void pci_disable_sriov(struct pci_dev *dev);
+
+(b) For the second method, from sysfs::
+
+ echo 0 > \
+ /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_numvfs
+
+To enable auto probing VFs by a compatible driver on the host, run
+command below before enabling SR-IOV capabilities. This is the
+default behavior.
+::
+
+ echo 1 > \
+ /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe
+
+To disable auto probing VFs by a compatible driver on the host, run
+command below before enabling SR-IOV capabilities. Updating this
+entry will not affect VFs which are already probed.
+::
+
+ echo 0 > \
+ /sys/bus/pci/devices/<DOMAIN:BUS:DEVICE.FUNCTION>/sriov_drivers_autoprobe
+
+Usage example
+-------------
+
+Following piece of code illustrates the usage of the SR-IOV API.
+::
+
+ static int dev_probe(struct pci_dev *dev, const struct pci_device_id *id)
+ {
+ pci_enable_sriov(dev, NR_VIRTFN);
+
+ ...
+
+ return 0;
+ }
+
+ static void dev_remove(struct pci_dev *dev)
+ {
+ pci_disable_sriov(dev);
+
+ ...
+ }
+
+ static int dev_suspend(struct pci_dev *dev, pm_message_t state)
+ {
+ ...
+
+ return 0;
+ }
+
+ static int dev_resume(struct pci_dev *dev)
+ {
+ ...
+
+ return 0;
+ }
+
+ static void dev_shutdown(struct pci_dev *dev)
+ {
+ ...
+ }
+
+ static int dev_sriov_configure(struct pci_dev *dev, int numvfs)
+ {
+ if (numvfs > 0) {
+ ...
+ pci_enable_sriov(dev, numvfs);
+ ...
+ return numvfs;
+ }
+ if (numvfs == 0) {
+ ....
+ pci_disable_sriov(dev);
+ ...
+ return 0;
+ }
+ }
+
+ static struct pci_driver dev_driver = {
+ .name = "SR-IOV Physical Function driver",
+ .id_table = dev_id_table,
+ .probe = dev_probe,
+ .remove = dev_remove,
+ .suspend = dev_suspend,
+ .resume = dev_resume,
+ .shutdown = dev_shutdown,
+ .sriov_configure = dev_sriov_configure,
+ };
diff --git a/Documentation/PCI/pci.rst b/Documentation/PCI/pci.rst
new file mode 100644
index 000000000..814b40f83
--- /dev/null
+++ b/Documentation/PCI/pci.rst
@@ -0,0 +1,577 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================
+How To Write Linux PCI Drivers
+==============================
+
+:Authors: - Martin Mares <mj@ucw.cz>
+ - Grant Grundler <grundler@parisc-linux.org>
+
+The world of PCI is vast and full of (mostly unpleasant) surprises.
+Since each CPU architecture implements different chip-sets and PCI devices
+have different requirements (erm, "features"), the result is the PCI support
+in the Linux kernel is not as trivial as one would wish. This short paper
+tries to introduce all potential driver authors to Linux APIs for
+PCI device drivers.
+
+A more complete resource is the third edition of "Linux Device Drivers"
+by Jonathan Corbet, Alessandro Rubini, and Greg Kroah-Hartman.
+LDD3 is available for free (under Creative Commons License) from:
+https://lwn.net/Kernel/LDD3/.
+
+However, keep in mind that all documents are subject to "bit rot".
+Refer to the source code if things are not working as described here.
+
+Please send questions/comments/patches about Linux PCI API to the
+"Linux PCI" <linux-pci@atrey.karlin.mff.cuni.cz> mailing list.
+
+
+Structure of PCI drivers
+========================
+PCI drivers "discover" PCI devices in a system via pci_register_driver().
+Actually, it's the other way around. When the PCI generic code discovers
+a new device, the driver with a matching "description" will be notified.
+Details on this below.
+
+pci_register_driver() leaves most of the probing for devices to
+the PCI layer and supports online insertion/removal of devices [thus
+supporting hot-pluggable PCI, CardBus, and Express-Card in a single driver].
+pci_register_driver() call requires passing in a table of function
+pointers and thus dictates the high level structure of a driver.
+
+Once the driver knows about a PCI device and takes ownership, the
+driver generally needs to perform the following initialization:
+
+ - Enable the device
+ - Request MMIO/IOP resources
+ - Set the DMA mask size (for both coherent and streaming DMA)
+ - Allocate and initialize shared control data (pci_allocate_coherent())
+ - Access device configuration space (if needed)
+ - Register IRQ handler (request_irq())
+ - Initialize non-PCI (i.e. LAN/SCSI/etc parts of the chip)
+ - Enable DMA/processing engines
+
+When done using the device, and perhaps the module needs to be unloaded,
+the driver needs to take the follow steps:
+
+ - Disable the device from generating IRQs
+ - Release the IRQ (free_irq())
+ - Stop all DMA activity
+ - Release DMA buffers (both streaming and coherent)
+ - Unregister from other subsystems (e.g. scsi or netdev)
+ - Release MMIO/IOP resources
+ - Disable the device
+
+Most of these topics are covered in the following sections.
+For the rest look at LDD3 or <linux/pci.h> .
+
+If the PCI subsystem is not configured (CONFIG_PCI is not set), most of
+the PCI functions described below are defined as inline functions either
+completely empty or just returning an appropriate error codes to avoid
+lots of ifdefs in the drivers.
+
+
+pci_register_driver() call
+==========================
+
+PCI device drivers call ``pci_register_driver()`` during their
+initialization with a pointer to a structure describing the driver
+(``struct pci_driver``):
+
+.. kernel-doc:: include/linux/pci.h
+ :functions: pci_driver
+
+The ID table is an array of ``struct pci_device_id`` entries ending with an
+all-zero entry. Definitions with static const are generally preferred.
+
+.. kernel-doc:: include/linux/mod_devicetable.h
+ :functions: pci_device_id
+
+Most drivers only need ``PCI_DEVICE()`` or ``PCI_DEVICE_CLASS()`` to set up
+a pci_device_id table.
+
+New PCI IDs may be added to a device driver pci_ids table at runtime
+as shown below::
+
+ echo "vendor device subvendor subdevice class class_mask driver_data" > \
+ /sys/bus/pci/drivers/{driver}/new_id
+
+All fields are passed in as hexadecimal values (no leading 0x).
+The vendor and device fields are mandatory, the others are optional. Users
+need pass only as many optional fields as necessary:
+
+ - subvendor and subdevice fields default to PCI_ANY_ID (FFFFFFFF)
+ - class and classmask fields default to 0
+ - driver_data defaults to 0UL.
+
+Note that driver_data must match the value used by any of the pci_device_id
+entries defined in the driver. This makes the driver_data field mandatory
+if all the pci_device_id entries have a non-zero driver_data value.
+
+Once added, the driver probe routine will be invoked for any unclaimed
+PCI devices listed in its (newly updated) pci_ids list.
+
+When the driver exits, it just calls pci_unregister_driver() and the PCI layer
+automatically calls the remove hook for all devices handled by the driver.
+
+
+"Attributes" for driver functions/data
+--------------------------------------
+
+Please mark the initialization and cleanup functions where appropriate
+(the corresponding macros are defined in <linux/init.h>):
+
+ ====== =================================================
+ __init Initialization code. Thrown away after the driver
+ initializes.
+ __exit Exit code. Ignored for non-modular drivers.
+ ====== =================================================
+
+Tips on when/where to use the above attributes:
+ - The module_init()/module_exit() functions (and all
+ initialization functions called _only_ from these)
+ should be marked __init/__exit.
+
+ - Do not mark the struct pci_driver.
+
+ - Do NOT mark a function if you are not sure which mark to use.
+ Better to not mark the function than mark the function wrong.
+
+
+How to find PCI devices manually
+================================
+
+PCI drivers should have a really good reason for not using the
+pci_register_driver() interface to search for PCI devices.
+The main reason PCI devices are controlled by multiple drivers
+is because one PCI device implements several different HW services.
+E.g. combined serial/parallel port/floppy controller.
+
+A manual search may be performed using the following constructs:
+
+Searching by vendor and device ID::
+
+ struct pci_dev *dev = NULL;
+ while (dev = pci_get_device(VENDOR_ID, DEVICE_ID, dev))
+ configure_device(dev);
+
+Searching by class ID (iterate in a similar way)::
+
+ pci_get_class(CLASS_ID, dev)
+
+Searching by both vendor/device and subsystem vendor/device ID::
+
+ pci_get_subsys(VENDOR_ID,DEVICE_ID, SUBSYS_VENDOR_ID, SUBSYS_DEVICE_ID, dev).
+
+You can use the constant PCI_ANY_ID as a wildcard replacement for
+VENDOR_ID or DEVICE_ID. This allows searching for any device from a
+specific vendor, for example.
+
+These functions are hotplug-safe. They increment the reference count on
+the pci_dev that they return. You must eventually (possibly at module unload)
+decrement the reference count on these devices by calling pci_dev_put().
+
+
+Device Initialization Steps
+===========================
+
+As noted in the introduction, most PCI drivers need the following steps
+for device initialization:
+
+ - Enable the device
+ - Request MMIO/IOP resources
+ - Set the DMA mask size (for both coherent and streaming DMA)
+ - Allocate and initialize shared control data (pci_allocate_coherent())
+ - Access device configuration space (if needed)
+ - Register IRQ handler (request_irq())
+ - Initialize non-PCI (i.e. LAN/SCSI/etc parts of the chip)
+ - Enable DMA/processing engines.
+
+The driver can access PCI config space registers at any time.
+(Well, almost. When running BIST, config space can go away...but
+that will just result in a PCI Bus Master Abort and config reads
+will return garbage).
+
+
+Enable the PCI device
+---------------------
+Before touching any device registers, the driver needs to enable
+the PCI device by calling pci_enable_device(). This will:
+
+ - wake up the device if it was in suspended state,
+ - allocate I/O and memory regions of the device (if BIOS did not),
+ - allocate an IRQ (if BIOS did not).
+
+.. note::
+ pci_enable_device() can fail! Check the return value.
+
+.. warning::
+ OS BUG: we don't check resource allocations before enabling those
+ resources. The sequence would make more sense if we called
+ pci_request_resources() before calling pci_enable_device().
+ Currently, the device drivers can't detect the bug when two
+ devices have been allocated the same range. This is not a common
+ problem and unlikely to get fixed soon.
+
+ This has been discussed before but not changed as of 2.6.19:
+ https://lore.kernel.org/r/20060302180025.GC28895@flint.arm.linux.org.uk/
+
+
+pci_set_master() will enable DMA by setting the bus master bit
+in the PCI_COMMAND register. It also fixes the latency timer value if
+it's set to something bogus by the BIOS. pci_clear_master() will
+disable DMA by clearing the bus master bit.
+
+If the PCI device can use the PCI Memory-Write-Invalidate transaction,
+call pci_set_mwi(). This enables the PCI_COMMAND bit for Mem-Wr-Inval
+and also ensures that the cache line size register is set correctly.
+Check the return value of pci_set_mwi() as not all architectures
+or chip-sets may support Memory-Write-Invalidate. Alternatively,
+if Mem-Wr-Inval would be nice to have but is not required, call
+pci_try_set_mwi() to have the system do its best effort at enabling
+Mem-Wr-Inval.
+
+
+Request MMIO/IOP resources
+--------------------------
+Memory (MMIO), and I/O port addresses should NOT be read directly
+from the PCI device config space. Use the values in the pci_dev structure
+as the PCI "bus address" might have been remapped to a "host physical"
+address by the arch/chip-set specific kernel support.
+
+See Documentation/driver-api/io-mapping.rst for how to access device registers
+or device memory.
+
+The device driver needs to call pci_request_region() to verify
+no other device is already using the same address resource.
+Conversely, drivers should call pci_release_region() AFTER
+calling pci_disable_device().
+The idea is to prevent two devices colliding on the same address range.
+
+.. tip::
+ See OS BUG comment above. Currently (2.6.19), The driver can only
+ determine MMIO and IO Port resource availability _after_ calling
+ pci_enable_device().
+
+Generic flavors of pci_request_region() are request_mem_region()
+(for MMIO ranges) and request_region() (for IO Port ranges).
+Use these for address resources that are not described by "normal" PCI
+BARs.
+
+Also see pci_request_selected_regions() below.
+
+
+Set the DMA mask size
+---------------------
+.. note::
+ If anything below doesn't make sense, please refer to
+ :doc:`/core-api/dma-api`. This section is just a reminder that
+ drivers need to indicate DMA capabilities of the device and is not
+ an authoritative source for DMA interfaces.
+
+While all drivers should explicitly indicate the DMA capability
+(e.g. 32 or 64 bit) of the PCI bus master, devices with more than
+32-bit bus master capability for streaming data need the driver
+to "register" this capability by calling pci_set_dma_mask() with
+appropriate parameters. In general this allows more efficient DMA
+on systems where System RAM exists above 4G _physical_ address.
+
+Drivers for all PCI-X and PCIe compliant devices must call
+pci_set_dma_mask() as they are 64-bit DMA devices.
+
+Similarly, drivers must also "register" this capability if the device
+can directly address "consistent memory" in System RAM above 4G physical
+address by calling pci_set_consistent_dma_mask().
+Again, this includes drivers for all PCI-X and PCIe compliant devices.
+Many 64-bit "PCI" devices (before PCI-X) and some PCI-X devices are
+64-bit DMA capable for payload ("streaming") data but not control
+("consistent") data.
+
+
+Setup shared control data
+-------------------------
+Once the DMA masks are set, the driver can allocate "consistent" (a.k.a. shared)
+memory. See :doc:`/core-api/dma-api` for a full description of
+the DMA APIs. This section is just a reminder that it needs to be done
+before enabling DMA on the device.
+
+
+Initialize device registers
+---------------------------
+Some drivers will need specific "capability" fields programmed
+or other "vendor specific" register initialized or reset.
+E.g. clearing pending interrupts.
+
+
+Register IRQ handler
+--------------------
+While calling request_irq() is the last step described here,
+this is often just another intermediate step to initialize a device.
+This step can often be deferred until the device is opened for use.
+
+All interrupt handlers for IRQ lines should be registered with IRQF_SHARED
+and use the devid to map IRQs to devices (remember that all PCI IRQ lines
+can be shared).
+
+request_irq() will associate an interrupt handler and device handle
+with an interrupt number. Historically interrupt numbers represent
+IRQ lines which run from the PCI device to the Interrupt controller.
+With MSI and MSI-X (more below) the interrupt number is a CPU "vector".
+
+request_irq() also enables the interrupt. Make sure the device is
+quiesced and does not have any interrupts pending before registering
+the interrupt handler.
+
+MSI and MSI-X are PCI capabilities. Both are "Message Signaled Interrupts"
+which deliver interrupts to the CPU via a DMA write to a Local APIC.
+The fundamental difference between MSI and MSI-X is how multiple
+"vectors" get allocated. MSI requires contiguous blocks of vectors
+while MSI-X can allocate several individual ones.
+
+MSI capability can be enabled by calling pci_alloc_irq_vectors() with the
+PCI_IRQ_MSI and/or PCI_IRQ_MSIX flags before calling request_irq(). This
+causes the PCI support to program CPU vector data into the PCI device
+capability registers. Many architectures, chip-sets, or BIOSes do NOT
+support MSI or MSI-X and a call to pci_alloc_irq_vectors with just
+the PCI_IRQ_MSI and PCI_IRQ_MSIX flags will fail, so try to always
+specify PCI_IRQ_LEGACY as well.
+
+Drivers that have different interrupt handlers for MSI/MSI-X and
+legacy INTx should chose the right one based on the msi_enabled
+and msix_enabled flags in the pci_dev structure after calling
+pci_alloc_irq_vectors.
+
+There are (at least) two really good reasons for using MSI:
+
+1) MSI is an exclusive interrupt vector by definition.
+ This means the interrupt handler doesn't have to verify
+ its device caused the interrupt.
+
+2) MSI avoids DMA/IRQ race conditions. DMA to host memory is guaranteed
+ to be visible to the host CPU(s) when the MSI is delivered. This
+ is important for both data coherency and avoiding stale control data.
+ This guarantee allows the driver to omit MMIO reads to flush
+ the DMA stream.
+
+See drivers/infiniband/hw/mthca/ or drivers/net/tg3.c for examples
+of MSI/MSI-X usage.
+
+
+PCI device shutdown
+===================
+
+When a PCI device driver is being unloaded, most of the following
+steps need to be performed:
+
+ - Disable the device from generating IRQs
+ - Release the IRQ (free_irq())
+ - Stop all DMA activity
+ - Release DMA buffers (both streaming and consistent)
+ - Unregister from other subsystems (e.g. scsi or netdev)
+ - Disable device from responding to MMIO/IO Port addresses
+ - Release MMIO/IO Port resource(s)
+
+
+Stop IRQs on the device
+-----------------------
+How to do this is chip/device specific. If it's not done, it opens
+the possibility of a "screaming interrupt" if (and only if)
+the IRQ is shared with another device.
+
+When the shared IRQ handler is "unhooked", the remaining devices
+using the same IRQ line will still need the IRQ enabled. Thus if the
+"unhooked" device asserts IRQ line, the system will respond assuming
+it was one of the remaining devices asserted the IRQ line. Since none
+of the other devices will handle the IRQ, the system will "hang" until
+it decides the IRQ isn't going to get handled and masks the IRQ (100,000
+iterations later). Once the shared IRQ is masked, the remaining devices
+will stop functioning properly. Not a nice situation.
+
+This is another reason to use MSI or MSI-X if it's available.
+MSI and MSI-X are defined to be exclusive interrupts and thus
+are not susceptible to the "screaming interrupt" problem.
+
+
+Release the IRQ
+---------------
+Once the device is quiesced (no more IRQs), one can call free_irq().
+This function will return control once any pending IRQs are handled,
+"unhook" the drivers IRQ handler from that IRQ, and finally release
+the IRQ if no one else is using it.
+
+
+Stop all DMA activity
+---------------------
+It's extremely important to stop all DMA operations BEFORE attempting
+to deallocate DMA control data. Failure to do so can result in memory
+corruption, hangs, and on some chip-sets a hard crash.
+
+Stopping DMA after stopping the IRQs can avoid races where the
+IRQ handler might restart DMA engines.
+
+While this step sounds obvious and trivial, several "mature" drivers
+didn't get this step right in the past.
+
+
+Release DMA buffers
+-------------------
+Once DMA is stopped, clean up streaming DMA first.
+I.e. unmap data buffers and return buffers to "upstream"
+owners if there is one.
+
+Then clean up "consistent" buffers which contain the control data.
+
+See :doc:`/core-api/dma-api` for details on unmapping interfaces.
+
+
+Unregister from other subsystems
+--------------------------------
+Most low level PCI device drivers support some other subsystem
+like USB, ALSA, SCSI, NetDev, Infiniband, etc. Make sure your
+driver isn't losing resources from that other subsystem.
+If this happens, typically the symptom is an Oops (panic) when
+the subsystem attempts to call into a driver that has been unloaded.
+
+
+Disable Device from responding to MMIO/IO Port addresses
+--------------------------------------------------------
+io_unmap() MMIO or IO Port resources and then call pci_disable_device().
+This is the symmetric opposite of pci_enable_device().
+Do not access device registers after calling pci_disable_device().
+
+
+Release MMIO/IO Port Resource(s)
+--------------------------------
+Call pci_release_region() to mark the MMIO or IO Port range as available.
+Failure to do so usually results in the inability to reload the driver.
+
+
+How to access PCI config space
+==============================
+
+You can use `pci_(read|write)_config_(byte|word|dword)` to access the config
+space of a device represented by `struct pci_dev *`. All these functions return
+0 when successful or an error code (`PCIBIOS_...`) which can be translated to a
+text string by pcibios_strerror. Most drivers expect that accesses to valid PCI
+devices don't fail.
+
+If you don't have a struct pci_dev available, you can call
+`pci_bus_(read|write)_config_(byte|word|dword)` to access a given device
+and function on that bus.
+
+If you access fields in the standard portion of the config header, please
+use symbolic names of locations and bits declared in <linux/pci.h>.
+
+If you need to access Extended PCI Capability registers, just call
+pci_find_capability() for the particular capability and it will find the
+corresponding register block for you.
+
+
+Other interesting functions
+===========================
+
+============================= ================================================
+pci_get_domain_bus_and_slot() Find pci_dev corresponding to given domain,
+ bus and slot and number. If the device is
+ found, its reference count is increased.
+pci_set_power_state() Set PCI Power Management state (0=D0 ... 3=D3)
+pci_find_capability() Find specified capability in device's capability
+ list.
+pci_resource_start() Returns bus start address for a given PCI region
+pci_resource_end() Returns bus end address for a given PCI region
+pci_resource_len() Returns the byte length of a PCI region
+pci_set_drvdata() Set private driver data pointer for a pci_dev
+pci_get_drvdata() Return private driver data pointer for a pci_dev
+pci_set_mwi() Enable Memory-Write-Invalidate transactions.
+pci_clear_mwi() Disable Memory-Write-Invalidate transactions.
+============================= ================================================
+
+
+Miscellaneous hints
+===================
+
+When displaying PCI device names to the user (for example when a driver wants
+to tell the user what card has it found), please use pci_name(pci_dev).
+
+Always refer to the PCI devices by a pointer to the pci_dev structure.
+All PCI layer functions use this identification and it's the only
+reasonable one. Don't use bus/slot/function numbers except for very
+special purposes -- on systems with multiple primary buses their semantics
+can be pretty complex.
+
+Don't try to turn on Fast Back to Back writes in your driver. All devices
+on the bus need to be capable of doing it, so this is something which needs
+to be handled by platform and generic code, not individual drivers.
+
+
+Vendor and device identifications
+=================================
+
+Do not add new device or vendor IDs to include/linux/pci_ids.h unless they
+are shared across multiple drivers. You can add private definitions in
+your driver if they're helpful, or just use plain hex constants.
+
+The device IDs are arbitrary hex numbers (vendor controlled) and normally used
+only in a single location, the pci_device_id table.
+
+Please DO submit new vendor/device IDs to https://pci-ids.ucw.cz/.
+There's a mirror of the pci.ids file at https://github.com/pciutils/pciids.
+
+
+Obsolete functions
+==================
+
+There are several functions which you might come across when trying to
+port an old driver to the new PCI interface. They are no longer present
+in the kernel as they aren't compatible with hotplug or PCI domains or
+having sane locking.
+
+================= ===========================================
+pci_find_device() Superseded by pci_get_device()
+pci_find_subsys() Superseded by pci_get_subsys()
+pci_find_slot() Superseded by pci_get_domain_bus_and_slot()
+pci_get_slot() Superseded by pci_get_domain_bus_and_slot()
+================= ===========================================
+
+The alternative is the traditional PCI device driver that walks PCI
+device lists. This is still possible but discouraged.
+
+
+MMIO Space and "Write Posting"
+==============================
+
+Converting a driver from using I/O Port space to using MMIO space
+often requires some additional changes. Specifically, "write posting"
+needs to be handled. Many drivers (e.g. tg3, acenic, sym53c8xx_2)
+already do this. I/O Port space guarantees write transactions reach the PCI
+device before the CPU can continue. Writes to MMIO space allow the CPU
+to continue before the transaction reaches the PCI device. HW weenies
+call this "Write Posting" because the write completion is "posted" to
+the CPU before the transaction has reached its destination.
+
+Thus, timing sensitive code should add readl() where the CPU is
+expected to wait before doing other work. The classic "bit banging"
+sequence works fine for I/O Port space::
+
+ for (i = 8; --i; val >>= 1) {
+ outb(val & 1, ioport_reg); /* write bit */
+ udelay(10);
+ }
+
+The same sequence for MMIO space should be::
+
+ for (i = 8; --i; val >>= 1) {
+ writeb(val & 1, mmio_reg); /* write bit */
+ readb(safe_mmio_reg); /* flush posted write */
+ udelay(10);
+ }
+
+It is important that "safe_mmio_reg" not have any side effects that
+interferes with the correct operation of the device.
+
+Another case to watch out for is when resetting a PCI device. Use PCI
+Configuration space reads to flush the writel(). This will gracefully
+handle the PCI master abort on all platforms if the PCI device is
+expected to not respond to a readl(). Most x86 platforms will allow
+MMIO reads to master abort (a.k.a. "Soft Fail") and return garbage
+(e.g. ~0). But many RISC platforms will crash (a.k.a."Hard Fail").
diff --git a/Documentation/PCI/pcieaer-howto.rst b/Documentation/PCI/pcieaer-howto.rst
new file mode 100644
index 000000000..0b36b9ebf
--- /dev/null
+++ b/Documentation/PCI/pcieaer-howto.rst
@@ -0,0 +1,300 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+===========================================================
+The PCI Express Advanced Error Reporting Driver Guide HOWTO
+===========================================================
+
+:Authors: - T. Long Nguyen <tom.l.nguyen@intel.com>
+ - Yanmin Zhang <yanmin.zhang@intel.com>
+
+:Copyright: |copy| 2006 Intel Corporation
+
+Overview
+===========
+
+About this guide
+----------------
+
+This guide describes the basics of the PCI Express Advanced Error
+Reporting (AER) driver and provides information on how to use it, as
+well as how to enable the drivers of endpoint devices to conform with
+PCI Express AER driver.
+
+
+What is the PCI Express AER Driver?
+-----------------------------------
+
+PCI Express error signaling can occur on the PCI Express link itself
+or on behalf of transactions initiated on the link. PCI Express
+defines two error reporting paradigms: the baseline capability and
+the Advanced Error Reporting capability. The baseline capability is
+required of all PCI Express components providing a minimum defined
+set of error reporting requirements. Advanced Error Reporting
+capability is implemented with a PCI Express advanced error reporting
+extended capability structure providing more robust error reporting.
+
+The PCI Express AER driver provides the infrastructure to support PCI
+Express Advanced Error Reporting capability. The PCI Express AER
+driver provides three basic functions:
+
+ - Gathers the comprehensive error information if errors occurred.
+ - Reports error to the users.
+ - Performs error recovery actions.
+
+AER driver only attaches root ports which support PCI-Express AER
+capability.
+
+
+User Guide
+==========
+
+Include the PCI Express AER Root Driver into the Linux Kernel
+-------------------------------------------------------------
+
+The PCI Express AER Root driver is a Root Port service driver attached
+to the PCI Express Port Bus driver. If a user wants to use it, the driver
+has to be compiled. Option CONFIG_PCIEAER supports this capability. It
+depends on CONFIG_PCIEPORTBUS, so pls. set CONFIG_PCIEPORTBUS=y and
+CONFIG_PCIEAER = y.
+
+Load PCI Express AER Root Driver
+--------------------------------
+
+Some systems have AER support in firmware. Enabling Linux AER support at
+the same time the firmware handles AER may result in unpredictable
+behavior. Therefore, Linux does not handle AER events unless the firmware
+grants AER control to the OS via the ACPI _OSC method. See the PCI FW 3.0
+Specification for details regarding _OSC usage.
+
+AER error output
+----------------
+
+When a PCIe AER error is captured, an error message will be output to
+console. If it's a correctable error, it is output as a warning.
+Otherwise, it is printed as an error. So users could choose different
+log level to filter out correctable error messages.
+
+Below shows an example::
+
+ 0000:50:00.0: PCIe Bus Error: severity=Uncorrected (Fatal), type=Transaction Layer, id=0500(Requester ID)
+ 0000:50:00.0: device [8086:0329] error status/mask=00100000/00000000
+ 0000:50:00.0: [20] Unsupported Request (First)
+ 0000:50:00.0: TLP Header: 04000001 00200a03 05010000 00050100
+
+In the example, 'Requester ID' means the ID of the device who sends
+the error message to root port. Pls. refer to pci express specs for
+other fields.
+
+AER Statistics / Counters
+-------------------------
+
+When PCIe AER errors are captured, the counters / statistics are also exposed
+in the form of sysfs attributes which are documented at
+Documentation/ABI/testing/sysfs-bus-pci-devices-aer_stats
+
+Developer Guide
+===============
+
+To enable AER aware support requires a software driver to configure
+the AER capability structure within its device and to provide callbacks.
+
+To support AER better, developers need understand how AER does work
+firstly.
+
+PCI Express errors are classified into two types: correctable errors
+and uncorrectable errors. This classification is based on the impacts
+of those errors, which may result in degraded performance or function
+failure.
+
+Correctable errors pose no impacts on the functionality of the
+interface. The PCI Express protocol can recover without any software
+intervention or any loss of data. These errors are detected and
+corrected by hardware. Unlike correctable errors, uncorrectable
+errors impact functionality of the interface. Uncorrectable errors
+can cause a particular transaction or a particular PCI Express link
+to be unreliable. Depending on those error conditions, uncorrectable
+errors are further classified into non-fatal errors and fatal errors.
+Non-fatal errors cause the particular transaction to be unreliable,
+but the PCI Express link itself is fully functional. Fatal errors, on
+the other hand, cause the link to be unreliable.
+
+When AER is enabled, a PCI Express device will automatically send an
+error message to the PCIe root port above it when the device captures
+an error. The Root Port, upon receiving an error reporting message,
+internally processes and logs the error message in its PCI Express
+capability structure. Error information being logged includes storing
+the error reporting agent's requestor ID into the Error Source
+Identification Registers and setting the error bits of the Root Error
+Status Register accordingly. If AER error reporting is enabled in Root
+Error Command Register, the Root Port generates an interrupt if an
+error is detected.
+
+Note that the errors as described above are related to the PCI Express
+hierarchy and links. These errors do not include any device specific
+errors because device specific errors will still get sent directly to
+the device driver.
+
+Configure the AER capability structure
+--------------------------------------
+
+AER aware drivers of PCI Express component need change the device
+control registers to enable AER. They also could change AER registers,
+including mask and severity registers. Helper function
+pci_enable_pcie_error_reporting could be used to enable AER. See
+section 3.3.
+
+Provide callbacks
+-----------------
+
+callback reset_link to reset pci express link
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This callback is used to reset the pci express physical link when a
+fatal error happens. The root port aer service driver provides a
+default reset_link function, but different upstream ports might
+have different specifications to reset pci express link, so all
+upstream ports should provide their own reset_link functions.
+
+Section 3.2.2.2 provides more detailed info on when to call
+reset_link.
+
+PCI error-recovery callbacks
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The PCI Express AER Root driver uses error callbacks to coordinate
+with downstream device drivers associated with a hierarchy in question
+when performing error recovery actions.
+
+Data struct pci_driver has a pointer, err_handler, to point to
+pci_error_handlers who consists of a couple of callback function
+pointers. AER driver follows the rules defined in
+pci-error-recovery.txt except pci express specific parts (e.g.
+reset_link). Pls. refer to pci-error-recovery.txt for detailed
+definitions of the callbacks.
+
+Below sections specify when to call the error callback functions.
+
+Correctable errors
+~~~~~~~~~~~~~~~~~~
+
+Correctable errors pose no impacts on the functionality of
+the interface. The PCI Express protocol can recover without any
+software intervention or any loss of data. These errors do not
+require any recovery actions. The AER driver clears the device's
+correctable error status register accordingly and logs these errors.
+
+Non-correctable (non-fatal and fatal) errors
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+If an error message indicates a non-fatal error, performing link reset
+at upstream is not required. The AER driver calls error_detected(dev,
+pci_channel_io_normal) to all drivers associated within a hierarchy in
+question. for example::
+
+ EndPoint<==>DownstreamPort B<==>UpstreamPort A<==>RootPort
+
+If Upstream port A captures an AER error, the hierarchy consists of
+Downstream port B and EndPoint.
+
+A driver may return PCI_ERS_RESULT_CAN_RECOVER,
+PCI_ERS_RESULT_DISCONNECT, or PCI_ERS_RESULT_NEED_RESET, depending on
+whether it can recover or the AER driver calls mmio_enabled as next.
+
+If an error message indicates a fatal error, kernel will broadcast
+error_detected(dev, pci_channel_io_frozen) to all drivers within
+a hierarchy in question. Then, performing link reset at upstream is
+necessary. As different kinds of devices might use different approaches
+to reset link, AER port service driver is required to provide the
+function to reset link via callback parameter of pcie_do_recovery()
+function. If reset_link is not NULL, recovery function will use it
+to reset the link. If error_detected returns PCI_ERS_RESULT_CAN_RECOVER
+and reset_link returns PCI_ERS_RESULT_RECOVERED, the error handling goes
+to mmio_enabled.
+
+helper functions
+----------------
+::
+
+ int pci_enable_pcie_error_reporting(struct pci_dev *dev);
+
+pci_enable_pcie_error_reporting enables the device to send error
+messages to root port when an error is detected. Note that devices
+don't enable the error reporting by default, so device drivers need
+call this function to enable it.
+
+::
+
+ int pci_disable_pcie_error_reporting(struct pci_dev *dev);
+
+pci_disable_pcie_error_reporting disables the device to send error
+messages to root port when an error is detected.
+
+::
+
+ int pci_aer_clear_nonfatal_status(struct pci_dev *dev);`
+
+pci_aer_clear_nonfatal_status clears non-fatal errors in the uncorrectable
+error status register.
+
+Frequent Asked Questions
+------------------------
+
+Q:
+ What happens if a PCI Express device driver does not provide an
+ error recovery handler (pci_driver->err_handler is equal to NULL)?
+
+A:
+ The devices attached with the driver won't be recovered. If the
+ error is fatal, kernel will print out warning messages. Please refer
+ to section 3 for more information.
+
+Q:
+ What happens if an upstream port service driver does not provide
+ callback reset_link?
+
+A:
+ Fatal error recovery will fail if the errors are reported by the
+ upstream ports who are attached by the service driver.
+
+Q:
+ How does this infrastructure deal with driver that is not PCI
+ Express aware?
+
+A:
+ This infrastructure calls the error callback functions of the
+ driver when an error happens. But if the driver is not aware of
+ PCI Express, the device might not report its own errors to root
+ port.
+
+Q:
+ What modifications will that driver need to make it compatible
+ with the PCI Express AER Root driver?
+
+A:
+ It could call the helper functions to enable AER in devices and
+ cleanup uncorrectable status register. Pls. refer to section 3.3.
+
+
+Software error injection
+========================
+
+Debugging PCIe AER error recovery code is quite difficult because it
+is hard to trigger real hardware errors. Software based error
+injection can be used to fake various kinds of PCIe errors.
+
+First you should enable PCIe AER software error injection in kernel
+configuration, that is, following item should be in your .config.
+
+CONFIG_PCIEAER_INJECT=y or CONFIG_PCIEAER_INJECT=m
+
+After reboot with new kernel or insert the module, a device file named
+/dev/aer_inject should be created.
+
+Then, you need a user space tool named aer-inject, which can be gotten
+from:
+
+ https://git.kernel.org/cgit/linux/kernel/git/gong.chen/aer-inject.git/
+
+More information about aer-inject can be found in the document comes
+with its source code.
diff --git a/Documentation/PCI/pciebus-howto.rst b/Documentation/PCI/pciebus-howto.rst
new file mode 100644
index 000000000..f882ff62c
--- /dev/null
+++ b/Documentation/PCI/pciebus-howto.rst
@@ -0,0 +1,220 @@
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+===========================================
+The PCI Express Port Bus Driver Guide HOWTO
+===========================================
+
+:Author: Tom L Nguyen tom.l.nguyen@intel.com 11/03/2004
+:Copyright: |copy| 2004 Intel Corporation
+
+About this guide
+================
+
+This guide describes the basics of the PCI Express Port Bus driver
+and provides information on how to enable the service drivers to
+register/unregister with the PCI Express Port Bus Driver.
+
+
+What is the PCI Express Port Bus Driver
+=======================================
+
+A PCI Express Port is a logical PCI-PCI Bridge structure. There
+are two types of PCI Express Port: the Root Port and the Switch
+Port. The Root Port originates a PCI Express link from a PCI Express
+Root Complex and the Switch Port connects PCI Express links to
+internal logical PCI buses. The Switch Port, which has its secondary
+bus representing the switch's internal routing logic, is called the
+switch's Upstream Port. The switch's Downstream Port is bridging from
+switch's internal routing bus to a bus representing the downstream
+PCI Express link from the PCI Express Switch.
+
+A PCI Express Port can provide up to four distinct functions,
+referred to in this document as services, depending on its port type.
+PCI Express Port's services include native hotplug support (HP),
+power management event support (PME), advanced error reporting
+support (AER), and virtual channel support (VC). These services may
+be handled by a single complex driver or be individually distributed
+and handled by corresponding service drivers.
+
+Why use the PCI Express Port Bus Driver?
+========================================
+
+In existing Linux kernels, the Linux Device Driver Model allows a
+physical device to be handled by only a single driver. The PCI
+Express Port is a PCI-PCI Bridge device with multiple distinct
+services. To maintain a clean and simple solution each service
+may have its own software service driver. In this case several
+service drivers will compete for a single PCI-PCI Bridge device.
+For example, if the PCI Express Root Port native hotplug service
+driver is loaded first, it claims a PCI-PCI Bridge Root Port. The
+kernel therefore does not load other service drivers for that Root
+Port. In other words, it is impossible to have multiple service
+drivers load and run on a PCI-PCI Bridge device simultaneously
+using the current driver model.
+
+To enable multiple service drivers running simultaneously requires
+having a PCI Express Port Bus driver, which manages all populated
+PCI Express Ports and distributes all provided service requests
+to the corresponding service drivers as required. Some key
+advantages of using the PCI Express Port Bus driver are listed below:
+
+ - Allow multiple service drivers to run simultaneously on
+ a PCI-PCI Bridge Port device.
+
+ - Allow service drivers implemented in an independent
+ staged approach.
+
+ - Allow one service driver to run on multiple PCI-PCI Bridge
+ Port devices.
+
+ - Manage and distribute resources of a PCI-PCI Bridge Port
+ device to requested service drivers.
+
+Configuring the PCI Express Port Bus Driver vs. Service Drivers
+===============================================================
+
+Including the PCI Express Port Bus Driver Support into the Kernel
+-----------------------------------------------------------------
+
+Including the PCI Express Port Bus driver depends on whether the PCI
+Express support is included in the kernel config. The kernel will
+automatically include the PCI Express Port Bus driver as a kernel
+driver when the PCI Express support is enabled in the kernel.
+
+Enabling Service Driver Support
+-------------------------------
+
+PCI device drivers are implemented based on Linux Device Driver Model.
+All service drivers are PCI device drivers. As discussed above, it is
+impossible to load any service driver once the kernel has loaded the
+PCI Express Port Bus Driver. To meet the PCI Express Port Bus Driver
+Model requires some minimal changes on existing service drivers that
+imposes no impact on the functionality of existing service drivers.
+
+A service driver is required to use the two APIs shown below to
+register its service with the PCI Express Port Bus driver (see
+section 5.2.1 & 5.2.2). It is important that a service driver
+initializes the pcie_port_service_driver data structure, included in
+header file /include/linux/pcieport_if.h, before calling these APIs.
+Failure to do so will result an identity mismatch, which prevents
+the PCI Express Port Bus driver from loading a service driver.
+
+pcie_port_service_register
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+::
+
+ int pcie_port_service_register(struct pcie_port_service_driver *new)
+
+This API replaces the Linux Driver Model's pci_register_driver API. A
+service driver should always calls pcie_port_service_register at
+module init. Note that after service driver being loaded, calls
+such as pci_enable_device(dev) and pci_set_master(dev) are no longer
+necessary since these calls are executed by the PCI Port Bus driver.
+
+pcie_port_service_unregister
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+::
+
+ void pcie_port_service_unregister(struct pcie_port_service_driver *new)
+
+pcie_port_service_unregister replaces the Linux Driver Model's
+pci_unregister_driver. It's always called by service driver when a
+module exits.
+
+Sample Code
+~~~~~~~~~~~
+
+Below is sample service driver code to initialize the port service
+driver data structure.
+::
+
+ static struct pcie_port_service_id service_id[] = { {
+ .vendor = PCI_ANY_ID,
+ .device = PCI_ANY_ID,
+ .port_type = PCIE_RC_PORT,
+ .service_type = PCIE_PORT_SERVICE_AER,
+ }, { /* end: all zeroes */ }
+ };
+
+ static struct pcie_port_service_driver root_aerdrv = {
+ .name = (char *)device_name,
+ .id_table = &service_id[0],
+
+ .probe = aerdrv_load,
+ .remove = aerdrv_unload,
+
+ .suspend = aerdrv_suspend,
+ .resume = aerdrv_resume,
+ };
+
+Below is a sample code for registering/unregistering a service
+driver.
+::
+
+ static int __init aerdrv_service_init(void)
+ {
+ int retval = 0;
+
+ retval = pcie_port_service_register(&root_aerdrv);
+ if (!retval) {
+ /*
+ * FIX ME
+ */
+ }
+ return retval;
+ }
+
+ static void __exit aerdrv_service_exit(void)
+ {
+ pcie_port_service_unregister(&root_aerdrv);
+ }
+
+ module_init(aerdrv_service_init);
+ module_exit(aerdrv_service_exit);
+
+Possible Resource Conflicts
+===========================
+
+Since all service drivers of a PCI-PCI Bridge Port device are
+allowed to run simultaneously, below lists a few of possible resource
+conflicts with proposed solutions.
+
+MSI and MSI-X Vector Resource
+-----------------------------
+
+Once MSI or MSI-X interrupts are enabled on a device, it stays in this
+mode until they are disabled again. Since service drivers of the same
+PCI-PCI Bridge port share the same physical device, if an individual
+service driver enables or disables MSI/MSI-X mode it may result
+unpredictable behavior.
+
+To avoid this situation all service drivers are not permitted to
+switch interrupt mode on its device. The PCI Express Port Bus driver
+is responsible for determining the interrupt mode and this should be
+transparent to service drivers. Service drivers need to know only
+the vector IRQ assigned to the field irq of struct pcie_device, which
+is passed in when the PCI Express Port Bus driver probes each service
+driver. Service drivers should use (struct pcie_device*)dev->irq to
+call request_irq/free_irq. In addition, the interrupt mode is stored
+in the field interrupt_mode of struct pcie_device.
+
+PCI Memory/IO Mapped Regions
+----------------------------
+
+Service drivers for PCI Express Power Management (PME), Advanced
+Error Reporting (AER), Hot-Plug (HP) and Virtual Channel (VC) access
+PCI configuration space on the PCI Express port. In all cases the
+registers accessed are independent of each other. This patch assumes
+that all service drivers will be well behaved and not overwrite
+other service driver's configuration settings.
+
+PCI Config Registers
+--------------------
+
+Each service driver runs its PCI config operations on its own
+capability structure except the PCI Express capability structure, in
+which Root Control register and Device Control register are shared
+between PME and AER. This patch assumes that all service drivers
+will be well behaved and not overwrite other service driver's
+configuration settings.
diff --git a/Documentation/PCI/sysfs-pci.rst b/Documentation/PCI/sysfs-pci.rst
new file mode 100644
index 000000000..742fbd21d
--- /dev/null
+++ b/Documentation/PCI/sysfs-pci.rst
@@ -0,0 +1,138 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+============================================
+Accessing PCI device resources through sysfs
+============================================
+
+sysfs, usually mounted at /sys, provides access to PCI resources on platforms
+that support it. For example, a given bus might look like this::
+
+ /sys/devices/pci0000:17
+ |-- 0000:17:00.0
+ | |-- class
+ | |-- config
+ | |-- device
+ | |-- enable
+ | |-- irq
+ | |-- local_cpus
+ | |-- remove
+ | |-- resource
+ | |-- resource0
+ | |-- resource1
+ | |-- resource2
+ | |-- revision
+ | |-- rom
+ | |-- subsystem_device
+ | |-- subsystem_vendor
+ | `-- vendor
+ `-- ...
+
+The topmost element describes the PCI domain and bus number. In this case,
+the domain number is 0000 and the bus number is 17 (both values are in hex).
+This bus contains a single function device in slot 0. The domain and bus
+numbers are reproduced for convenience. Under the device directory are several
+files, each with their own function.
+
+ =================== =====================================================
+ file function
+ =================== =====================================================
+ class PCI class (ascii, ro)
+ config PCI config space (binary, rw)
+ device PCI device (ascii, ro)
+ enable Whether the device is enabled (ascii, rw)
+ irq IRQ number (ascii, ro)
+ local_cpus nearby CPU mask (cpumask, ro)
+ remove remove device from kernel's list (ascii, wo)
+ resource PCI resource host addresses (ascii, ro)
+ resource0..N PCI resource N, if present (binary, mmap, rw\ [1]_)
+ resource0_wc..N_wc PCI WC map resource N, if prefetchable (binary, mmap)
+ revision PCI revision (ascii, ro)
+ rom PCI ROM resource, if present (binary, ro)
+ subsystem_device PCI subsystem device (ascii, ro)
+ subsystem_vendor PCI subsystem vendor (ascii, ro)
+ vendor PCI vendor (ascii, ro)
+ =================== =====================================================
+
+::
+
+ ro - read only file
+ rw - file is readable and writable
+ wo - write only file
+ mmap - file is mmapable
+ ascii - file contains ascii text
+ binary - file contains binary data
+ cpumask - file contains a cpumask type
+
+.. [1] rw for IORESOURCE_IO (I/O port) regions only
+
+The read only files are informational, writes to them will be ignored, with
+the exception of the 'rom' file. Writable files can be used to perform
+actions on the device (e.g. changing config space, detaching a device).
+mmapable files are available via an mmap of the file at offset 0 and can be
+used to do actual device programming from userspace. Note that some platforms
+don't support mmapping of certain resources, so be sure to check the return
+value from any attempted mmap. The most notable of these are I/O port
+resources, which also provide read/write access.
+
+The 'enable' file provides a counter that indicates how many times the device
+has been enabled. If the 'enable' file currently returns '4', and a '1' is
+echoed into it, it will then return '5'. Echoing a '0' into it will decrease
+the count. Even when it returns to 0, though, some of the initialisation
+may not be reversed.
+
+The 'rom' file is special in that it provides read-only access to the device's
+ROM file, if available. It's disabled by default, however, so applications
+should write the string "1" to the file to enable it before attempting a read
+call, and disable it following the access by writing "0" to the file. Note
+that the device must be enabled for a rom read to return data successfully.
+In the event a driver is not bound to the device, it can be enabled using the
+'enable' file, documented above.
+
+The 'remove' file is used to remove the PCI device, by writing a non-zero
+integer to the file. This does not involve any kind of hot-plug functionality,
+e.g. powering off the device. The device is removed from the kernel's list of
+PCI devices, the sysfs directory for it is removed, and the device will be
+removed from any drivers attached to it. Removal of PCI root buses is
+disallowed.
+
+Accessing legacy resources through sysfs
+----------------------------------------
+
+Legacy I/O port and ISA memory resources are also provided in sysfs if the
+underlying platform supports them. They're located in the PCI class hierarchy,
+e.g.::
+
+ /sys/class/pci_bus/0000:17/
+ |-- bridge -> ../../../devices/pci0000:17
+ |-- cpuaffinity
+ |-- legacy_io
+ `-- legacy_mem
+
+The legacy_io file is a read/write file that can be used by applications to
+do legacy port I/O. The application should open the file, seek to the desired
+port (e.g. 0x3e8) and do a read or a write of 1, 2 or 4 bytes. The legacy_mem
+file should be mmapped with an offset corresponding to the memory offset
+desired, e.g. 0xa0000 for the VGA frame buffer. The application can then
+simply dereference the returned pointer (after checking for errors of course)
+to access legacy memory space.
+
+Supporting PCI access on new platforms
+--------------------------------------
+
+In order to support PCI resource mapping as described above, Linux platform
+code should ideally define ARCH_GENERIC_PCI_MMAP_RESOURCE and use the generic
+implementation of that functionality. To support the historical interface of
+mmap() through files in /proc/bus/pci, platforms may also set HAVE_PCI_MMAP.
+
+Alternatively, platforms which set HAVE_PCI_MMAP may provide their own
+implementation of pci_mmap_page_range() instead of defining
+ARCH_GENERIC_PCI_MMAP_RESOURCE.
+
+Platforms which support write-combining maps of PCI resources must define
+arch_can_pci_mmap_wc() which shall evaluate to non-zero at runtime when
+write-combining is permitted. Platforms which support maps of I/O resources
+define arch_can_pci_mmap_io() similarly.
+
+Legacy resources are protected by the HAVE_PCI_LEGACY define. Platforms
+wishing to support legacy functionality should define it and provide
+pci_legacy_read, pci_legacy_write and pci_mmap_legacy_page_range functions.
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-06 08:09:52 +0000