Re: [PATCH] PCI/PM: Mark devices disconnected if their upstream PCIe link is down on resume

[Lukas Wunner <lukas@wunner.de>]

On Mon, Sep 18, 2023 at 08:30:41AM +0300, Mika Westerberg wrote:
> Mark Blakeney reported that when suspending system with a Thunderbolt
> dock connected and then unplugging the dock before resume (which is
> pretty normal flow with laptops), resuming takes long time.
> 
> What happens is that the PCIe link from the root port to the PCIe switch
> inside the Thunderbolt device does not train (as expected, the link is
> upplugged):
> 
> [   34.903158] pcieport 0000:00:07.2: restoring config space at offset 0x24 (was 0x3bf12001, writing 0x3bf12001)
> [   34.903231] pcieport 0000:00:07.0: waiting 100 ms for downstream link
> [   36.140616] pcieport 0000:01:00.0: not ready 1023ms after resume; giving up
> 
> However, at this point we still try the resume the devices below that
> unplugged link:
> 
> [   36.140741] pcieport 0000:01:00.0: Unable to change power state from D3cold to D0, device inaccessible
> ...
> [   36.142235] pcieport 0000:01:00.0: restoring config space at offset 0x38 (was 0xffffffff, writing 0x0)
> ...
> [   36.144702] pcieport 0000:02:02.0: waiting 100 ms for downstream link, after activation
> 
> And this is the link from PCIe switch downstream port to the xHCI on the
> dock:
> 
> [   38.380618] xhci_hcd 0000:03:00.0: not ready 1023ms after resume; waiting
> [   39.420587] xhci_hcd 0000:03:00.0: not ready 2047ms after resume; waiting
> [   41.527250] xhci_hcd 0000:03:00.0: not ready 4095ms after resume; waiting
> [   45.793957] xhci_hcd 0000:03:00.0: not ready 8191ms after resume; waiting
> [   54.113950] xhci_hcd 0000:03:00.0: not ready 16383ms after resume; waiting
> [   71.180576] xhci_hcd 0000:03:00.0: not ready 32767ms after resume; waiting
> ...
> [  105.313963] xhci_hcd 0000:03:00.0: not ready 65535ms after resume; giving up
> [  105.314037] xhci_hcd 0000:03:00.0: Unable to change power state from D3cold to D0, device inaccessible
> [  105.315640] xhci_hcd 0000:03:00.0: restoring config space at offset 0x3c (was 0xffffffff, writing 0x1ff)
> ...
> 
> This ends up slowing down the resume time considerably. For this reason
> mark these devices as disconnected if the link above them did not train
> properly.
> 
> Fixes: e8b908146d44 ("PCI/PM: Increase wait time after resume")
> Reported-by: Mark Blakeney <mark.blakeney@bullet-systems.net>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217915
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Reviewed-by: Lukas Wunner <lukas@wunner.de>