1 PCI bus bridges have standardized Device Tree bindings:
3 PCI Bus Binding to: IEEE Std 1275-1994
4 http://www.devicetree.org/open-firmware/bindings/pci/pci2_1.pdf
6 And for the interrupt mapping part:
8 Open Firmware Recommended Practice: Interrupt Mapping
9 http://www.devicetree.org/open-firmware/practice/imap/imap0_9d.pdf
11 Additionally to the properties specified in the above standards a host bridge
12 driver implementation may support the following properties:
15 If present this property assigns a fixed PCI domain number to a host bridge,
16 otherwise an unstable (across boots) unique number will be assigned.
17 It is required to either not set this property at all or set it for all
18 host bridges in the system, otherwise potentially conflicting domain numbers
19 may be assigned to root buses behind different host bridges. The domain
20 number for each host bridge in the system must be unique.
22 If present this property specifies PCI gen for link capability. Host
23 drivers could add this as a strategy to avoid unnecessary operation for
24 unsupported link speed, for instance, trying to do training for
25 unsupported link speed, etc. Must be '4' for gen4, '3' for gen3, '2'
26 for gen2, and '1' for gen1. Any other values are invalid.
28 PCI-PCI Bridge properties
29 -------------------------
31 PCIe root ports and switch ports may be described explicitly in the device
32 tree, as children of the host bridge node. Even though those devices are
33 discoverable by probing, it might be necessary to describe properties that
34 aren't provided by standard PCIe capabilities.
39 Identifies the PCI-PCI bridge. As defined in the IEEE Std 1275-1994
40 document, it is a five-cell address encoded as (phys.hi phys.mid
41 phys.lo size.hi size.lo). phys.hi should contain the device's BDF as
42 0b00000000 bbbbbbbb dddddfff 00000000. The other cells should be zero.
44 The bus number is defined by firmware, through the standard bridge
45 configuration mechanism. If this port is a switch port, then firmware
46 allocates the bus number and writes it into the Secondary Bus Number
47 register of the bridge directly above this port. Otherwise, the bus
48 number of a root port is the first number in the bus-range property,
51 If firmware leaves the ARI Forwarding Enable bit set in the bridge
52 above this port, then phys.hi contains the 8-bit function number as
53 0b00000000 bbbbbbbb ffffffff 00000000. Note that the PCIe specification
54 recommends that firmware only leaves ARI enabled when it knows that the
60 When present, the port is external-facing. All bridges and endpoints
61 downstream of this port are external to the machine. The OS can, for
62 example, use this information to identify devices that cannot be
63 trusted with relaxed DMA protection, as users could easily attach
64 malicious devices to this port.
69 compatible = "pci-host-ecam-generic";
72 /* Root port 00:01.0 is external-facing */
73 reg = <0x00000800 0 0 0 0>;