USB transfers in device drivers

Thu May 2 11:04:12 UTC 2019

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.

--HPS