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MdeModulePkg: Enable PciBus to handle CRS responses by ignoring the device. #11012

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MdeModulePkg: Enable PciBus to handle CRS responses by ignoring the device. #11012

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35 changes: 23 additions & 12 deletions MdeModulePkg/Bus/Pci/PciBusDxe/PciEnumeratorSupport.c
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Original file line number Diff line number Diff line change
Expand Up @@ -59,19 +59,30 @@ PciDevicePresent (
Pci
);

if (!EFI_ERROR (Status) && ((Pci->Hdr).VendorId != 0xffff)) {
//
// Read the entire config header for the device
//
Status = PciRootBridgeIo->Pci.Read (
PciRootBridgeIo,
EfiPciWidthUint32,
Address,
sizeof (PCI_TYPE00) / sizeof (UINT32),
Pci
);
//
// The host bridge may be programmed to accept Configuration Retry Status (CRS). If the PCI device
// is slow, and CRS is enabled, the VendorId may read as 0x0001 when not ready.
// This value is assigned to the PCI-SIG for this, and other purposes.
// PCI EXPRESS BASE SPECIFICATION, REV. 3.1 section 2.3.1.
// Skip the device, as all the other data read will be invalid.
//
if (!EFI_ERROR (Status)) {
if (((Pci->Hdr).VendorId != 0xffff) && ((Pci->Hdr).VendorId != 0x0001)) {
//
// Read the entire config header for the device
//
Status = PciRootBridgeIo->Pci.Read (
PciRootBridgeIo,
EfiPciWidthUint32,
Address,
sizeof (PCI_TYPE00) / sizeof (UINT32),
Pci
);

return EFI_SUCCESS;
return EFI_SUCCESS;
} else if ((Pci->Hdr).VendorId == 0x0001) {
DEBUG ((DEBUG_WARN, "CRS response detected. Devices that return a CRS response during enumeration are currently ignored\n"));
}
}

return EFI_NOT_FOUND;
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