Re: [PATCH v2] PCI: pciehp: Ignore Link Down/Up caused by DPC

[Lukas Wunner <lukas@wunner.de>]

On Fri, Jun 25, 2021 at 03:38:41PM -0500, stuart hayes wrote:
> I have a system that is failing to recover after an EDR event with (or
> without...) this patch.  It looks like the problem is similar to what this
> patch is trying to fix, except that on my system, the hotplug port is
> downstream of the root port that has DPC, so the "link down" event on it is
> not being ignored.  So the hotplug code disables the slot (which contains an
> NVMe device on this system) while the nvme driver is trying to use it, which
> results in a failed recovery and another EDR event, and the kernel ends up
> with the DPC trigger status bit set in the root port, so everything
> downstream is gone.
> 
> I added the hack below so the hotplug code will ignore the "link down"
> events on the ports downstream of the root port during DPC recovery, and it
> recovers no problem.  (I'm not proposing this as a correct fix.)

Could you test if the below patch fixes the issue?

Note, this is a hack as well, but I can turn it into a proper patch
if it works as expected.

Thanks!

Lukas

-- >8 --

diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index c7ff1eea225a..893c7ae1a54d 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -160,6 +160,10 @@ static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
 
 static pci_ers_result_t pcie_portdrv_slot_reset(struct pci_dev *dev)
 {
+	if (dev->is_hotplug_bridge)
+		pcie_capability_write_word(dev, PCI_EXP_SLTSTA,
+					   PCI_EXP_SLTSTA_DLLSC);
+
 	pci_restore_state(dev);
 	pci_save_state(dev);
 	return PCI_ERS_RESULT_RECOVERED;