Re: diagnosing resume failures after disconnected USB4 drives (Was: Re: PCI/ASPM: Fix L1SS saving (linus/master commit 7507eb3e7bfac))

Lukas Wunner
2025-03-06T16:45:26Z

On Tue, Mar 04, 2025 at 10:23:14AM +0200, Mika Westerberg wrote:
> Unfortunately I still see the same hang. I double checked, with revert the
> problem goes a way and with this patch I still see it.
>
> Steps:
>
> 1. Boot the system, nothing connected.
> 2. Connect TBT 4 dock to the host.
> 3. Connect TBT 3 NVMe to the TBT4 doc.
> 4. Authorize both PCIe tunnels, verify devices are there.
> 5. Enter s2idle.
> 6. Unplug the TBT 4 dock from the host.
> 7. Exit s2idle.

Thanks for testing. Would you mind giving the below a spin?

I've realized this can likely be solved in a much easier way:

The ->resume_noirq callback is invoked while traversing down
the hierarchy and the topmost slot which detects device replacement
already marks everything below as disconnected. Hence any nested
hotplug ports can just skip the replacement check because they're
disconnected as well.

-- >8 --

diff --git a/drivers/pci/hotplug/pciehp_core.c b/drivers/pci/hotplug/pciehp_core.c
index ff458e6..997841c 100644
--- a/drivers/pci/hotplug/pciehp_core.c
+++ b/drivers/pci/hotplug/pciehp_core.c
@@ -286,9 +286,12 @@ static int pciehp_suspend(struct pcie_device *dev)

static bool pciehp_device_replaced(struct controller *ctrl)
{
- struct pci_dev *pdev __free(pci_dev_put);
+ struct pci_dev *pdev __free(pci_dev_put) = NULL;
u32 reg;

+ if (pci_dev_is_disconnected(ctrl->pcie->port))
+ return false;
+
pdev = pci_get_slot(ctrl->pcie->port->subordinate, PCI_DEVFN(0, 0));
if (!pdev)
return true;