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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-27 10:05:51 +0000 |
commit | 5d1646d90e1f2cceb9f0828f4b28318cd0ec7744 (patch) | |
tree | a94efe259b9009378be6d90eb30d2b019d95c194 /Documentation/devicetree/bindings/pci/pci.txt | |
parent | Initial commit. (diff) | |
download | linux-430c2fc249ea5c0536abd21c23382884005c9093.tar.xz linux-430c2fc249ea5c0536abd21c23382884005c9093.zip |
Adding upstream version 5.10.209.upstream/5.10.209upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'Documentation/devicetree/bindings/pci/pci.txt')
-rw-r--r-- | Documentation/devicetree/bindings/pci/pci.txt | 84 |
1 files changed, 84 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt new file mode 100644 index 000000000..6a8f2874a --- /dev/null +++ b/Documentation/devicetree/bindings/pci/pci.txt @@ -0,0 +1,84 @@ +PCI bus bridges have standardized Device Tree bindings: + +PCI Bus Binding to: IEEE Std 1275-1994 +https://www.devicetree.org/open-firmware/bindings/pci/pci2_1.pdf + +And for the interrupt mapping part: + +Open Firmware Recommended Practice: Interrupt Mapping +https://www.devicetree.org/open-firmware/practice/imap/imap0_9d.pdf + +Additionally to the properties specified in the above standards a host bridge +driver implementation may support the following properties: + +- linux,pci-domain: + If present this property assigns a fixed PCI domain number to a host bridge, + otherwise an unstable (across boots) unique number will be assigned. + It is required to either not set this property at all or set it for all + host bridges in the system, otherwise potentially conflicting domain numbers + may be assigned to root buses behind different host bridges. The domain + number for each host bridge in the system must be unique. +- max-link-speed: + If present this property specifies PCI gen for link capability. Host + drivers could add this as a strategy to avoid unnecessary operation for + unsupported link speed, for instance, trying to do training for + unsupported link speed, etc. Must be '4' for gen4, '3' for gen3, '2' + for gen2, and '1' for gen1. Any other values are invalid. +- reset-gpios: + If present this property specifies PERST# GPIO. Host drivers can parse the + GPIO and apply fundamental reset to endpoints. +- supports-clkreq: + If present this property specifies that CLKREQ signal routing exists from + root port to downstream device and host bridge drivers can do programming + which depends on CLKREQ signal existence. For example, programming root port + not to advertise ASPM L1 Sub-States support if there is no CLKREQ signal. + +PCI-PCI Bridge properties +------------------------- + +PCIe root ports and switch ports may be described explicitly in the device +tree, as children of the host bridge node. Even though those devices are +discoverable by probing, it might be necessary to describe properties that +aren't provided by standard PCIe capabilities. + +Required properties: + +- reg: + Identifies the PCI-PCI bridge. As defined in the IEEE Std 1275-1994 + document, it is a five-cell address encoded as (phys.hi phys.mid + phys.lo size.hi size.lo). phys.hi should contain the device's BDF as + 0b00000000 bbbbbbbb dddddfff 00000000. The other cells should be zero. + + The bus number is defined by firmware, through the standard bridge + configuration mechanism. If this port is a switch port, then firmware + allocates the bus number and writes it into the Secondary Bus Number + register of the bridge directly above this port. Otherwise, the bus + number of a root port is the first number in the bus-range property, + defaulting to zero. + + If firmware leaves the ARI Forwarding Enable bit set in the bridge + above this port, then phys.hi contains the 8-bit function number as + 0b00000000 bbbbbbbb ffffffff 00000000. Note that the PCIe specification + recommends that firmware only leaves ARI enabled when it knows that the + OS is ARI-aware. + +Optional properties: + +- external-facing: + When present, the port is external-facing. All bridges and endpoints + downstream of this port are external to the machine. The OS can, for + example, use this information to identify devices that cannot be + trusted with relaxed DMA protection, as users could easily attach + malicious devices to this port. + +Example: + +pcie@10000000 { + compatible = "pci-host-ecam-generic"; + ... + pcie@0008 { + /* Root port 00:01.0 is external-facing */ + reg = <0x00000800 0 0 0 0>; + external-facing; + }; +}; |