Re: [PATCH] xhci: enable XHCI_TRUST_TX_LENGTH quirk for ThunderX2 builtin hosts

[Mathias Nyman <mathias.nyman@linux.intel.com>]

On 27.11.2019 18.16, Ard Biesheuvel wrote:
> On Wed, 27 Nov 2019 at 16:56, Mathias Nyman
> <mathias.nyman@linux.intel.com> wrote:
>>
>> On 27.11.2019 17.30, Ard Biesheuvel wrote:
>>> When using a USB webcam on a ThunderX2 workstation, the kernel log
>>> gets flooded with messages like
>>>
>>>     xhci_hcd 0000:00:0f.0:
>>>     WARN Successful completion on short TX for slot 7 ep 2: needs XHCI_TRUST_TX_LENGTH quirk?
>>>
>>> Enabling the quirk manually makes the issue go away, so let's enable
>>> it unconditionally for this hardware.
>>>
>>
>> This issue starts to be common for many vendors, many report successful
>> completions after a initial short transfer in a TD
>>
>> Does the patch below help in your case? It worked for a Renesas controller
>> with similar issues. It's a more generic solution.
>>
>> diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
>> index 9ebaa8e132a9..d23f7408c81f 100644
>> --- a/drivers/usb/host/xhci-ring.c
>> +++ b/drivers/usb/host/xhci-ring.c
>> @@ -2381,7 +2381,8 @@ static int handle_tx_event(struct xhci_hcd *xhci,
>>           case COMP_SUCCESS:
>>                   if (EVENT_TRB_LEN(le32_to_cpu(event->transfer_len)) == 0)
>>                           break;
>> -               if (xhci->quirks & XHCI_TRUST_TX_LENGTH)
>> +               if (xhci->quirks & XHCI_TRUST_TX_LENGTH ||
>> +                   ep_ring->last_td_was_short)
>>                           trb_comp_code = COMP_SHORT_PACKET;
>>                   else
>>                           xhci_warn_ratelimited(xhci,
> 
> Yes, that works too. If you roll that into a patch
> 
> Tested-by: Ard Biesheuvel <ardb@kernel.org>
> 
> and please consider cc'ing stable as well.
> 

Will do, thanks

-Mathias