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Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.. include:: <isonum.txt>
+
+=========================================================
+DPAA2 (Data Path Acceleration Architecture Gen2) Overview
+=========================================================
+
+:Copyright: |copy| 2015 Freescale Semiconductor Inc.
+:Copyright: |copy| 2018 NXP
+
+This document provides an overview of the Freescale DPAA2 architecture
+and how it is integrated into the Linux kernel.
+
+Introduction
+============
+
+DPAA2 is a hardware architecture designed for high-speeed network
+packet processing.  DPAA2 consists of sophisticated mechanisms for
+processing Ethernet packets, queue management, buffer management,
+autonomous L2 switching, virtual Ethernet bridging, and accelerator
+(e.g. crypto) sharing.
+
+A DPAA2 hardware component called the Management Complex (or MC) manages the
+DPAA2 hardware resources.  The MC provides an object-based abstraction for
+software drivers to use the DPAA2 hardware.
+The MC uses DPAA2 hardware resources such as queues, buffer pools, and
+network ports to create functional objects/devices such as network
+interfaces, an L2 switch, or accelerator instances.
+The MC provides memory-mapped I/O command interfaces (MC portals)
+which DPAA2 software drivers use to operate on DPAA2 objects.
+
+The diagram below shows an overview of the DPAA2 resource management
+architecture::
+
+	+--------------------------------------+
+	|                  OS                  |
+	|                        DPAA2 drivers |
+	|                             |        |
+	+-----------------------------|--------+
+	                              |
+	                              | (create,discover,connect
+	                              |  config,use,destroy)
+	                              |
+	                 DPAA2        |
+	+------------------------| mc portal |-+
+	|                             |        |
+	|   +- - - - - - - - - - - - -V- - -+  |
+	|   |                               |  |
+	|   |   Management Complex (MC)     |  |
+	|   |                               |  |
+	|   +- - - - - - - - - - - - - - - -+  |
+	|                                      |
+	| Hardware                  Hardware   |
+	| Resources                 Objects    |
+	| ---------                 -------    |
+	| -queues                   -DPRC      |
+	| -buffer pools             -DPMCP     |
+	| -Eth MACs/ports           -DPIO      |
+	| -network interface        -DPNI      |
+	|  profiles                 -DPMAC     |
+	| -queue portals            -DPBP      |
+	| -MC portals                ...       |
+	|  ...                                 |
+	|                                      |
+	+--------------------------------------+
+
+
+The MC mediates operations such as create, discover,
+connect, configuration, and destroy.  Fast-path operations
+on data, such as packet transmit/receive, are not mediated by
+the MC and are done directly using memory mapped regions in
+DPIO objects.
+
+Overview of DPAA2 Objects
+=========================
+
+The section provides a brief overview of some key DPAA2 objects.
+A simple scenario is described illustrating the objects involved
+in creating a network interfaces.
+
+DPRC (Datapath Resource Container)
+----------------------------------
+
+A DPRC is a container object that holds all the other
+types of DPAA2 objects.  In the example diagram below there
+are 8 objects of 5 types (DPMCP, DPIO, DPBP, DPNI, and DPMAC)
+in the container.
+
+::
+
+	+---------------------------------------------------------+
+	| DPRC                                                    |
+	|                                                         |
+	|  +-------+  +-------+  +-------+  +-------+  +-------+  |
+	|  | DPMCP |  | DPIO  |  | DPBP  |  | DPNI  |  | DPMAC |  |
+	|  +-------+  +-------+  +-------+  +---+---+  +---+---+  |
+	|  | DPMCP |  | DPIO  |                                   |
+	|  +-------+  +-------+                                   |
+	|  | DPMCP |                                              |
+	|  +-------+                                              |
+	|                                                         |
+	+---------------------------------------------------------+
+
+From the point of view of an OS, a DPRC behaves similar to a plug and
+play bus, like PCI.  DPRC commands can be used to enumerate the contents
+of the DPRC, discover the hardware objects present (including mappable
+regions and interrupts).
+
+::
+
+	DPRC.1 (bus)
+	   |
+	   +--+--------+-------+-------+-------+
+	      |        |       |       |       |
+	    DPMCP.1  DPIO.1  DPBP.1  DPNI.1  DPMAC.1
+	    DPMCP.2  DPIO.2
+	    DPMCP.3
+
+Hardware objects can be created and destroyed dynamically, providing
+the ability to hot plug/unplug objects in and out of the DPRC.
+
+A DPRC has a mappable MMIO region (an MC portal) that can be used
+to send MC commands.  It has an interrupt for status events (like
+hotplug).
+All objects in a container share the same hardware "isolation context".
+This means that with respect to an IOMMU the isolation granularity
+is at the DPRC (container) level, not at the individual object
+level.
+
+DPRCs can be defined statically and populated with objects
+via a config file passed to the MC when firmware starts it.
+
+DPAA2 Objects for an Ethernet Network Interface
+-----------------------------------------------
+
+A typical Ethernet NIC is monolithic-- the NIC device contains TX/RX
+queuing mechanisms, configuration mechanisms, buffer management,
+physical ports, and interrupts.  DPAA2 uses a more granular approach
+utilizing multiple hardware objects.  Each object provides specialized
+functions. Groups of these objects are used by software to provide
+Ethernet network interface functionality.  This approach provides
+efficient use of finite hardware resources, flexibility, and
+performance advantages.
+
+The diagram below shows the objects needed for a simple
+network interface configuration on a system with 2 CPUs.
+
+::
+
+	+---+---+ +---+---+
+	   CPU0     CPU1
+	+---+---+ +---+---+
+	    |         |
+	+---+---+ +---+---+
+	   DPIO     DPIO
+	+---+---+ +---+---+
+	    \     /
+	     \   /
+	      \ /
+	   +---+---+
+	      DPNI  --- DPBP,DPMCP
+	   +---+---+
+	       |
+	       |
+	   +---+---+
+	     DPMAC
+	   +---+---+
+	       |
+	   port/PHY
+
+Below the objects are described.  For each object a brief description
+is provided along with a summary of the kinds of operations the object
+supports and a summary of key resources of the object (MMIO regions
+and IRQs).
+
+DPMAC (Datapath Ethernet MAC)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Represents an Ethernet MAC, a hardware device that connects to an Ethernet
+PHY and allows physical transmission and reception of Ethernet frames.
+
+- MMIO regions: none
+- IRQs: DPNI link change
+- commands: set link up/down, link config, get stats,
+  IRQ config, enable, reset
+
+DPNI (Datapath Network Interface)
+Contains TX/RX queues, network interface configuration, and RX buffer pool
+configuration mechanisms.  The TX/RX queues are in memory and are identified
+by queue number.
+
+- MMIO regions: none
+- IRQs: link state
+- commands: port config, offload config, queue config,
+  parse/classify config, IRQ config, enable, reset
+
+DPIO (Datapath I/O)
+~~~~~~~~~~~~~~~~~~~
+Provides interfaces to enqueue and dequeue
+packets and do hardware buffer pool management operations.  The DPAA2
+architecture separates the mechanism to access queues (the DPIO object)
+from the queues themselves.  The DPIO provides an MMIO interface to
+enqueue/dequeue packets.  To enqueue something a descriptor is written
+to the DPIO MMIO region, which includes the target queue number.
+There will typically be one DPIO assigned to each CPU.  This allows all
+CPUs to simultaneously perform enqueue/dequeued operations.  DPIOs are
+expected to be shared by different DPAA2 drivers.
+
+- MMIO regions: queue operations, buffer management
+- IRQs: data availability, congestion notification, buffer
+  pool depletion
+- commands: IRQ config, enable, reset
+
+DPBP (Datapath Buffer Pool)
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Represents a hardware buffer pool.
+
+- MMIO regions: none
+- IRQs: none
+- commands: enable, reset
+
+DPMCP (Datapath MC Portal)
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+Provides an MC command portal.
+Used by drivers to send commands to the MC to manage
+objects.
+
+- MMIO regions: MC command portal
+- IRQs: command completion
+- commands: IRQ config, enable, reset
+
+Object Connections
+==================
+Some objects have explicit relationships that must
+be configured:
+
+- DPNI <--> DPMAC
+- DPNI <--> DPNI
+- DPNI <--> L2-switch-port
+
+    A DPNI must be connected to something such as a DPMAC,
+    another DPNI, or L2 switch port.  The DPNI connection
+    is made via a DPRC command.
+
+::
+
+              +-------+  +-------+
+              | DPNI  |  | DPMAC |
+              +---+---+  +---+---+
+                  |          |
+                  +==========+
+
+- DPNI <--> DPBP
+
+    A network interface requires a 'buffer pool' (DPBP
+    object) which provides a list of pointers to memory
+    where received Ethernet data is to be copied.  The
+    Ethernet driver configures the DPBPs associated with
+    the network interface.
+
+Interrupts
+==========
+All interrupts generated by DPAA2 objects are message
+interrupts.  At the hardware level message interrupts
+generated by devices will normally have 3 components--
+1) a non-spoofable 'device-id' expressed on the hardware
+bus, 2) an address, 3) a data value.
+
+In the case of DPAA2 devices/objects, all objects in the
+same container/DPRC share the same 'device-id'.
+For ARM-based SoC this is the same as the stream ID.
+
+
+DPAA2 Linux Drivers Overview
+============================
+
+This section provides an overview of the Linux kernel drivers for
+DPAA2-- 1) the bus driver and associated "DPAA2 infrastructure"
+drivers and 2) functional object drivers (such as Ethernet).
+
+As described previously, a DPRC is a container that holds the other
+types of DPAA2 objects.  It is functionally similar to a plug-and-play
+bus controller.
+Each object in the DPRC is a Linux "device" and is bound to a driver.
+The diagram below shows the Linux drivers involved in a networking
+scenario and the objects bound to each driver.  A brief description
+of each driver follows.
+
+::
+
+	                                     +------------+
+	                                     | OS Network |
+	                                     |   Stack    |
+	         +------------+              +------------+
+	         | Allocator  |. . . . . . . |  Ethernet  |
+	         |(DPMCP,DPBP)|              |   (DPNI)   |
+	         +-.----------+              +---+---+----+
+	          .          .                   ^   |
+	         .            .     <data avail, |   | <enqueue,
+	        .              .     tx confirm> |   | dequeue>
+	+-------------+         .                |   |
+	| DPRC driver |          .           +---+---V----+     +---------+
+	|   (DPRC)    |           . . . . . .| DPIO driver|     |   MAC   |
+	+----------+--+                      |  (DPIO)    |     | (DPMAC) |
+	           |                         +------+-----+     +-----+---+
+	           |<dev add/remove>                |                 |
+	           |                                |                 |
+	  +--------+----------+                     |              +--+---+
+	  |   MC-bus driver   |                     |              | PHY  |
+	  |                   |                     |              |driver|
+	  |   /bus/fsl-mc     |                     |              +--+---+
+	  +-------------------+                     |                 |
+	                                            |                 |
+	========================= HARDWARE =========|=================|======
+	                                          DPIO                |
+	                                            |                 |
+	                                          DPNI---DPBP         |
+	                                            |                 |
+	                                          DPMAC               |
+	                                            |                 |
+	                                           PHY ---------------+
+	============================================|========================
+
+A brief description of each driver is provided below.
+
+MC-bus driver
+-------------
+The MC-bus driver is a platform driver and is probed from a
+node in the device tree (compatible "fsl,qoriq-mc") passed in by boot
+firmware.  It is responsible for bootstrapping the DPAA2 kernel
+infrastructure.
+Key functions include:
+
+- registering a new bus type named "fsl-mc" with the kernel,
+  and implementing bus call-backs (e.g. match/uevent/dev_groups)
+- implementing APIs for DPAA2 driver registration and for device
+  add/remove
+- creates an MSI IRQ domain
+- doing a 'device add' to expose the 'root' DPRC, in turn triggering
+  a bind of the root DPRC to the DPRC driver
+
+The binding for the MC-bus device-tree node can be consulted at
+*Documentation/devicetree/bindings/misc/fsl,qoriq-mc.txt*.
+The sysfs bind/unbind interfaces for the MC-bus can be consulted at
+*Documentation/ABI/testing/sysfs-bus-fsl-mc*.
+
+DPRC driver
+-----------
+The DPRC driver is bound to DPRC objects and does runtime management
+of a bus instance.  It performs the initial bus scan of the DPRC
+and handles interrupts for container events such as hot plug by
+re-scanning the DPRC.
+
+Allocator
+---------
+Certain objects such as DPMCP and DPBP are generic and fungible,
+and are intended to be used by other drivers.  For example,
+the DPAA2 Ethernet driver needs:
+
+- DPMCPs to send MC commands, to configure network interfaces
+- DPBPs for network buffer pools
+
+The allocator driver registers for these allocatable object types
+and those objects are bound to the allocator when the bus is probed.
+The allocator maintains a pool of objects that are available for
+allocation by other DPAA2 drivers.
+
+DPIO driver
+-----------
+The DPIO driver is bound to DPIO objects and provides services that allow
+other drivers such as the Ethernet driver to enqueue and dequeue data for
+their respective objects.
+Key services include:
+
+- data availability notifications
+- hardware queuing operations (enqueue and dequeue of data)
+- hardware buffer pool management
+
+To transmit a packet the Ethernet driver puts data on a queue and
+invokes a DPIO API.  For receive, the Ethernet driver registers
+a data availability notification callback.  To dequeue a packet
+a DPIO API is used.
+There is typically one DPIO object per physical CPU for optimum
+performance, allowing different CPUs to simultaneously enqueue
+and dequeue data.
+
+The DPIO driver operates on behalf of all DPAA2 drivers
+active in the kernel--  Ethernet, crypto, compression,
+etc.
+
+Ethernet driver
+---------------
+The Ethernet driver is bound to a DPNI and implements the kernel
+interfaces needed to connect the DPAA2 network interface to
+the network stack.
+Each DPNI corresponds to a Linux network interface.
+
+MAC driver
+----------
+An Ethernet PHY is an off-chip, board specific component and is managed
+by the appropriate PHY driver via an mdio bus.  The MAC driver
+plays a role of being a proxy between the PHY driver and the
+MC.  It does this proxy via the MC commands to a DPMAC object.
+If the PHY driver signals a link change, the MAC driver notifies
+the MC via a DPMAC command.  If a network interface is brought
+up or down, the MC notifies the DPMAC driver via an interrupt and
+the driver can take appropriate action.