On 1/12/2024 10:36 PM, Bjorn Helgaas wrote:
External email: Use caution opening links or attachments
On Thu, Jan 04, 2024 at 07:02:29AM +0530, Vidya Sagar wrote:
If a downstream port has a PCIe switch connected to it, the enumeration
process leaves the 'Received Master Abort' bit set in the Secondary
Status Register of the downstream port because of the Unsupported
Requests (URs) take place in the downstream hierarchy. Since the
ownership of Secondary Status Register always lies with the OS including
systems with Firmware-First approach for error handling[1], clear the
error status bits in the Secondary Status Register post enumeration.
I would expect these URs to happen when enumerating below *all* PCIe
Root Ports (not just when switches are present), and Master Aborts
should happen in conventional PCI.
Agree.
There was a misunderstanding from my side because of which I had said
that the 'Received Master Abort' bit gets set only if there is a PCIe
switch connected downstream. I'll correct it in my next patch.
Similarly, I don't think Firmware-First is relevant here. Only the
fact that the OS owns PCI_SEC_STATUS because there's no mechanism to
negotiate for platform ownership of it.
I mentioned about Firmware-First as a continuation to the discussion we
had in [1]. But, agree that, this being a standalone patch, there is no
need to mentioned about Firmware-First flow.
We're in the merge window right now, so we'll start merging v6.9
material after v6.8-rc1 is tagged.
[1] https://lore.kernel.org/all/1fb9d746-0695-4d19-af98-f442f31cd464@xxxxxxxxxx/T/
Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
---
drivers/pci/probe.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 43159965e09e..edf8202465d8 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1470,6 +1470,9 @@ static int pci_scan_bridge_extend(struct pci_bus *bus, struct pci_dev *dev,
}
out:
+ /* Clear errors in the Secondary Status Register */
+ pci_write_config_word(dev, PCI_SEC_STATUS, 0xffff);
+
pci_write_config_word(dev, PCI_BRIDGE_CONTROL, bctl);
pm_runtime_put(&dev->dev);
--
2.25.1
