Re: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 4 comp_code 1

From: Fabian Melzow <fabian.melzow@gmail.com>
To: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: linux-usb@vger.kernel.org
Subject: Re: ERROR Transfer event TRB DMA ptr not part of current TD ep_index 4 comp_code 1
Date: Tue, 30 Jun 2020 18:58:03 +0200	[thread overview]
Message-ID: <20200630185803.2a72c123@ping> (raw)
In-Reply-To: <264e8287-b538-0798-36a6-7eafc4387a8d@linux.intel.com>

Hi!

Am Mon, 29 Jun 2020 20:47:24 +0300
schrieb Mathias Nyman <mathias.nyman@linux.intel.com>:

> First issue I see is that the attempt to recover from a transaction
> error with a soft retry isn't working. We expect the hardware to
> retry the transfer but nothing seems to happen. Soft retry is
> described in xhci specs 4.6.8.1 and is basically a reset endpoint
> command with TSP set, followed by ringing the endpoint doorbell.
> Traces indicate driver does this correctly but hardware isn't
> retrying. We get don't get any event, no error, success or stall.
> 
> This could be hardware flaw.
> Any chance you could try this on a xHC from some other vendor?

There is no other xHC hardware available to me.

> Second issue is a driver flaw, when nothing happened for 20 seconds
> we see the URB is canceled. xhci driver needs to stop then endpoint
> to cancel the URB, but there is a hw race and endpoint ends up halted
> instead of stopped. The xhci driver can't handle a halted endpoint in
> its stop endpoint handler properly, and the URB is never actually
> removed from the ring.
> 
> The reason you see the IO_PAGE_FAULT is probably because once the
> ring starts running the driver will handle the cancelled URB, and
> touch already freed memory: AMD-Vi: Event logged [IO_PAGE_FAULT
> domain=0x000d address=0xdc707028 flags=0x0020]
> 
> I have a patch for this second case, I haven't upstreamed it as it
> got some conflicting feedback earlier. It won't solve the 20 second
> delay, but should solve the the IO_PAGE_FAULT and the "WARN Set TR
> Deq Ptr cmd failed due to incorrect slot or ep state" message
> 
> Can you try it out?

I successful applied the patch against Linux 5.7.4, but get this error when
compiling drivers/usb/host/xhci-ring.c:

  CC [M]  drivers/usb/host/xhci-ring.o
drivers/usb/host/xhci-ring.c: In function ‘xhci_handle_cmd_stop_ep’:
drivers/usb/host/xhci-ring.c:857:3: error: implicit declaration of function ‘xhci_reset_halted_ep’ [-Werror=implicit-function-declaration]
  857 |   xhci_reset_halted_ep(xhci, slot_id, ep_index, reset_type);
      |   ^~~~~~~~~~~~~~~~~~~~

Fabian