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Some of the host drivers have the requirement of knowing whether the EP would never train at some link speed at all. For instance, on some boards, the link won't train at 5 GT/s but the host driver still sacrifice some cycles to wait for the result of training at 5 GT/s as the host could actually support 5 GT/s. So we could parse this new property and make the host drivers be aware of these cases. Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Rob Herring <robh@kernel.org>
27 lines
1.2 KiB
Plaintext
27 lines
1.2 KiB
Plaintext
PCI bus bridges have standardized Device Tree bindings:
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PCI Bus Binding to: IEEE Std 1275-1994
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http://www.firmware.org/1275/bindings/pci/pci2_1.pdf
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And for the interrupt mapping part:
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Open Firmware Recommended Practice: Interrupt Mapping
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http://www.firmware.org/1275/practice/imap/imap0_9d.pdf
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Additionally to the properties specified in the above standards a host bridge
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driver implementation may support the following properties:
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- linux,pci-domain:
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If present this property assigns a fixed PCI domain number to a host bridge,
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otherwise an unstable (across boots) unique number will be assigned.
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It is required to either not set this property at all or set it for all
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host bridges in the system, otherwise potentially conflicting domain numbers
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may be assigned to root buses behind different host bridges. The domain
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number for each host bridge in the system must be unique.
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- max-link-speed:
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If present this property specifies PCI gen for link capability. Host
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drivers could add this as a strategy to avoid unnecessary operation for
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unsupported link speed, for instance, trying to do training for
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unsupported link speed, etc. Must be '4' for gen4, '3' for gen3, '2'
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for gen2, and '1' for gen1. Any other values are invalid.
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