USB transfers in device drivers

[Hans Petter Selasky]

On 2019-05-02 13:38, O'Connor, Daniel wrote:
> 
> 
>> On 2 May 2019, at 20:33, Hans Petter Selasky <hps at selasky.org> wrote:
>>
>> On 2019-05-02 12:44, O'Connor, Daniel wrote:
>>>> On 2 May 2019, at 20:02, Hans Petter Selasky <hps at selasky.org> wrote:
>>>>
>>>> On 2019-05-02 11:18, O'Connor, Daniel wrote:
>>>>> OK, thanks.
>>>>> To be honest I would much prefer to work out why this particular hardware & software seem to drop the ball for such a long time - 50msec without the kernel getting to schedule something (on a basically idle system) is quite perplexing to me.
>>>>
>>>> Sounds like a lost IRQ issue. Did you try any of the EHCI quirks in hw.usb.ehci ?
>>> No not, yet - thanks for the pointer!
>>
>> The 50ms delay may also be due to a physical link data error and needed recovery through clear stall which is expensive.
>>
> 
> I see the same error on different hardware sets (both motherboard and USB device) so I don't think it's that.
> 

If you can check if a USB BULK transfer is pending during this delay, 
then it might also be a firmware issue.

--HPS