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SubjectRe: [PATCH] PCI: Disable upstream port PTM during suspend
On Wed, Jul 06, 2022 at 08:32:44PM +0800, Kai-Heng Feng wrote:
> On Intel Alder Lake platforms, Thunderbolt entering D3cold can cause
> some errors reported by AER:
> pcieport 0000:00:1d.0: AER: Uncorrected (Non-Fatal) error received: 0000:00:1d.0
> pcieport 0000:00:1d.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, (Requester ID)
> pcieport 0000:00:1d.0: device [8086:7ab0] error status/mask=00100000/00004000
> pcieport 0000:00:1d.0: [20] UnsupReq (First)
> pcieport 0000:00:1d.0: AER: TLP Header: 34000000 08000052 00000000 00000000
> thunderbolt 0000:0a:00.0: AER: can't recover (no error_detected callback)
> xhci_hcd 0000:3e:00.0: AER: can't recover (no error_detected callback)
> pcieport 0000:00:1d.0: AER: device recovery failed
>
> In addition to that, it can also block system from suspending when
> a Thunderbolt dock is attached to the same system.
>
> The original approach [1] is to disable AER and DPC when link is in
> L2/L3 Ready, L2 and L3, but Bjorn identified the root cause is the Unsupported
> Request:
> - 08:00.0 sent a PTM Request Message (a Posted Request)
> - 00:1d.0 received the PTM Request Message
> - The link transitioned to DL_Down
> - Per sec 2.9.1, 00:1d.0 discarded the Request and reported an
> Unsupported Request
> - Or, per sec 6.21.3, if 00:1d.0 received a PTM Request when its
> own PTM Enable was clear, it would also be treated as an
> Unsupported Request
>
> And further: 'David did something like this [1], but just for Root Ports. That
> looks wrong to me because sec 6.21.3 says we should not have PTM enabled in an
> Upstream Port (i.e., in a downstream device like 08:00.0) unless it is already
> enabled in the Downstream Port (i.e., in the Root Port 00:1d.0).'
>
> So also disable upstream port PTM to make the PCI driver conform to the spec
> and solve the issue.
>
> [1] https://lore.kernel.org/all/20220408153159.106741-1-kai.heng.feng@canonical.com/
> [2] https://lore.kernel.org/all/20220422222433.GA1464120@bhelgaas/
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=215453
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=216210
> Suggested-by: Bjorn Helgaas <bhelgaas@google.com>
> Cc: David E. Box <david.e.box@linux.intel.com>
> Cc: Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>
>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

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