MdeModulePkg: Enable PciBus to handle CRS responses by ignoring the device. #11012
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…evice. If there is a slow device on the PCI Bus, and the HostBridge is programmed to allow CRS, the slow device may return 0x0001 to inform the config space reader of the Vendor Id that pci device is not ready. The current PciBus enumerator will treat 0001 as a valid Vendor Id, but it is not. It indicates that all other config space is invalid. This code changes that operation to skip slow devices. PCI EXPRESS BASE SPECIFICATION, REV. 3.1 section 2.3.1 Request Handling Rules. Signed-off-by: Aaron Pop <[email protected]>
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Description
If there is a slow device on the PCI Bus, and the HostBridge is programmed to allow CRS, the slow device may return 0x0001 to inform the config space reader of the Vendor Id that pci device is not ready. The current PciBus enumerator will treat 0001 as a valid Vendor Id, but it is not. It indicates that all other config space is invalid. This code changes that operation to skip slow devices.
PCI EXPRESS BASE SPECIFICATION, REV. 3.1 section
2.3.1 Request Handling Rules.
How This Was Tested
Verified that with change platforms without CRS still boot.
Integration Instructions
No integration necessary.