Bug in split transactions on Raspberry Pi
stern at rowland.harvard.edu
Wed Jan 27 14:03:05 PST 2016
On Wed, 27 Jan 2016, Doug Anderson wrote:
> On Wed, Jan 27, 2016 at 1:34 PM, Alan Stern <stern at rowland.harvard.edu> wrote:
> > On Wed, 27 Jan 2016, Doug Anderson wrote:
> >> This patch should fix ya.
> >> FIXUP: FROMLIST: usb: dwc2: host: Manage frame nums better in scheduler
> >> https://chromium-review.googlesource.com/324185
> > Hmmm. That fixed the problem of the polls occuring too frequently, but
> > now I see again intervals that are larger than 256 ms. In the most
> > recent test there are two intervals of 512 ms and one of 2048 ms.
> OK, good to know. Ugh. I'll have to see if I can reproduce that. If
> I had to guess, though, I'd say that you're probably running into high
> interrupt latency problems.
Quite possibly. Would that delay the transfers by a full period or
only by one frame?
> Those problems would be worse on the
> Raspberry Pi than on my system due to the significantly slower
> Can you confirm that these problems also were introduced by my series?
> AKA: you never saw > 256 ms polls before my series and now you see
No, these problems were also present in the kernel without your
> Turning on scheduler tracing would probably be quite helpful at this
> point. You can see
> <https://chromium-review.googlesource.com/#/c/314254/>. If printing
> even non-verbose traces to the console is too much, you could make
> everything "trace_printk". You might also want
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