[mirror_ubuntu-artful-kernel.git] / Documentation / devicetree / bindings / pci / pci.txt

PCI bus bridges have standardized Device Tree bindings:

PCI Bus Binding to: IEEE Std 1275-1994
http://www.firmware.org/1275/bindings/pci/pci2_1.pdf

And for the interrupt mapping part:

Open Firmware Recommended Practice: Interrupt Mapping
http://www.firmware.org/1275/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.
Commit	Line	Data
301d2d87 LW	1	PCI bus bridges have standardized Device Tree bindings:
	2
	3	PCI Bus Binding to: IEEE Std 1275-1994
f517256a	4	http://www.firmware.org/1275/bindings/pci/pci2_1.pdf
301d2d87 LW	5
	6	And for the interrupt mapping part:
	7
	8	Open Firmware Recommended Practice: Interrupt Mapping
f517256a	9	http://www.firmware.org/1275/practice/imap/imap0_9d.pdf
2801f725 LS	10
	11	Additionally to the properties specified in the above standards a host bridge
	12	driver implementation may support the following properties:
	13
	14	- linux,pci-domain:
	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.
2fa39159 SL	21	- max-link-speed:
	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.