[RFC PATCH 2/3] PCI: aardvark: Correct Configuration RRS checking

Bjorn Helgaas
2024-08-27T23:49:08Z

From: Bjorn Helgaas <bhelgaas@google.com>

Per PCIe r6.0, sec 2.3.2, when a Root Complex handles a Completion with
Request Retry Status for a Configuration Read Request that includes both
bytes of the Vendor ID field, it must complete the Request to the host by
returning 0001h for the Vendor ID and all 1's for any additional bytes.

Previously we only returned the 0001h Vendor ID value if we got an RRS
completion for reads of exactly 4 bytes. A read of 2 bytes would not
qualify, although the spec says it should.

Check for reads of 2 or more bytes including the Vendor ID.

I don't think this will fix any observable problems because RRS only
applies to the first config reads after reset, and those are all currently
dword (4-byte) reads.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
drivers/pci/controller/pci-aardvark.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/pci/controller/pci-aardvark.c b/drivers/pci/controller/pci-aardvark.c
index 8b3e1a079cf3..e66594558ce2 100644
--- a/drivers/pci/controller/pci-aardvark.c
+++ b/drivers/pci/controller/pci-aardvark.c
@@ -1153,11 +1153,11 @@ static int advk_pcie_rd_conf(struct pci_bus *bus, u32 devfn,
size, val);

/*
- * Completion Retry Status is possible to return only when reading all
- * 4 bytes from PCI_VENDOR_ID and PCI_DEVICE_ID registers at once and
- * CRSSVE flag on Root Bridge is enabled.
+ * Completion Retry Status is possible to return only when reading
+ * both bytes from PCI_VENDOR_ID at once and CRSSVE flag on Root
+ * Port is enabled.
*/
- allow_crs = (where == PCI_VENDOR_ID) && (size == 4) &&
+ allow_crs = (where == PCI_VENDOR_ID) && (size >= 2) &&
(le16_to_cpu(pcie->bridge.pcie_conf.rootctl) &
PCI_EXP_RTCTL_CRSSVE);

--
2.34.1