USB transfers in device drivers

[O'Connor, Daniel]

> 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.

--
Daniel O'Connor
"The nice thing about standards is that there
are so many of them to choose from."
 -- Andrew Tanenbaum