Hi Mathias,

On 01/09/2021 10:21, Mathias Nyman wrote:

On 31.8.2021 19.02, Phil Elwell wrote:

quoted

From: Jonathan Bell <redacted>

See https://github.com/raspberrypi/linux/issues/3981

Thanks, so in a nutshell the issue looks something like:

[827586.220071] xhci_hcd 0000:01:00.0: WARN Cannot submit Set TR Deq Ptr
[827586.220087] xhci_hcd 0000:01:00.0: A Set TR Deq Ptr command is pending.
[827723.160680] INFO: task usb-storage:93 blocked for more than 122 seconds.

The blocked task is probably because xhci driver failed to give back the
URB after failing to submit a "Set TR Deq Ptr" command. This part should
be fixed in:
https://lore.kernel.org/r/20210820123503.2605901-4-mathias.nyman@linux.intel.com (local)
which is currently in usb-next, and should be in 5.15-rc1 and future 5.12+ stable.

quoted

Two read-modify-write cycles on ep->ep_state are not guarded by
xhci->lock. Fix these.

This is probably one cause for the "Warn Cannot submit Set TR Deq Ptr A Set TR
Deq Ptr command is pending" message.
Another possibility is that with UAS and streams we have several transfer rings
per endpoint, meaning that if two TDs on separate stream rings on the same
endpoint both stall, or are cancelled we could see this message.

The SET_DEQ_PENDING flag in ep->ep_state should probably be per ring, not per
endpoint. Then we also need a "rings_with_pending_set_deq" counter per endpoint
to keep track when all set_tr_deq commands complete, and we can restart the endpoint

Jonathan, the author of the patch, may give some detailed feedback on these 
statements when he has a moment - "Well, sort of... it's complicated" was the 
summary.

Anyway, my patch linked above together with this patch should make these errors
a lot more harmless.

Yes, I think that's true. We have a downstream patch to warn about a pending
Set TR Deq Ptr command but proceed anyway, allowing systems to recover, but with 
the additional spin lock usage our users are reporting no failures _and_ no
warnings.

Let me know if you can trigger the issue with both these patches applied.

We've not tried your patch yet.

I'll add your patch to the queue as well.

Many thanks,

Phil