[+cc Lukas, pciehp expert and author of a97396c6eb13]
On Fri, Jan 23, 2026 at 06:40:34PM +0800, LeoLiu-oc wrote:
> Commit a97396c6eb13 ("PCI: pciehp: Ignore Link Down/Up caused by DPC")
> amended PCIe hotplug to not bring down the slot upon Data Link Layer State
> Changed events caused by Downstream Port Containment.
>
> However, PCIe hotplug (pciehp) waits up to 4 seconds before assuming that
> DPC recovery has failed and disabling the slot. This timeout period is
> insufficient for some PCIe devices.
> For example, the E810 dual-port network card driver needs to take over
> 10 seconds to execute its err_detected() callback.
> Since this exceeds the maximum wait time allowed for DPC recovery by the
> hotplug IRQ threads, a race condition occurs between the hotplug thread and
> the dpc_handler() thread.
Add blank lines between paragraphs.
Include the name of the E810 driver so we can easily find the
.err_detected() callback in question. Actually, including the *name*
of that callback would be a very direct way of doing this :)
I guess the problem this fixes is that there was a PCIe error that
triggered DPC, and the E810 .err_detected() works but takes longer
than expected, which results in pciehp disabling the slot when it
doesn't need to? So the user basically sees a dead E810 device?
It seems unfortunate that we have this dependency on the time allowed
for .err_detected() to execute. It's nice if adding arbitrary delay
doesn't break things, but maybe we can't always achieve that.
I see that pci_dpc_recovered() is called from pciehp_ist(). Are we
prepared for long delays there?
> Signed-off-by: LeoLiu-oc <[email protected]>
> ---
> drivers/pci/pcie/dpc.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
> index fc18349614d7..08b5f275699a 100644
> --- a/drivers/pci/pcie/dpc.c
> +++ b/drivers/pci/pcie/dpc.c
> @@ -121,7 +121,7 @@ bool pci_dpc_recovered(struct pci_dev *pdev)
> * but reports indicate that DPC completes within 4 seconds.
> */
> wait_event_timeout(dpc_completed_waitqueue, dpc_completed(pdev),
> - msecs_to_jiffies(4000));
> + msecs_to_jiffies(16000));
It looks like this breaks the connection between the "completes within
4 seconds" comment and the 4000ms wait_event timeout.
> return test_and_clear_bit(PCI_DPC_RECOVERED, &pdev->priv_flags);
> }
> --
> 2.43.0
>
