Re: [PATCH 1/4] drm/i915: promote FIFO underruns to DRM_ERROR

Paulo Zanoni
2013-09-19T20:20:50Z

2013/9/19 Chris Wilson <chris@chris-wilson.co.uk>:
> On Thu, Sep 19, 2013 at 05:00:35PM -0300, Paulo Zanoni wrote:
>> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
>>
>> Linus recently complained about screen corruption when coming out of
>> DPMS on his Haswell machine, and he also mentioned there were no error
>> messages on the log. I think I can reproduce this problem, and when it
>> happens I get a "FIFO underrun" message, but since it's just
>> DRM_DEBUG_DRIVER it's hard to notice. So promote underruns to error
>> messages because reports containing "I'm getting a FIFO underrun on
>> pipe A" are way much better than "I'm getting a screen corruption".
>
> Sadly FIFO underruns on quite a few platforms are expected and
> unfixable. Others they are just expected. We reduced the error level
> because they are too noisy, and we were not in a position where the
> underrun was actionable. As we do not yet have the underrun feedback in
> place, I do not think we are ready for the onslaught of errors.
>
> At minimum, you should only set the error message for the platforms you
> intend to fix.

Hmmmm, yeah, I should have thought about this a little bit more. Sorry :(

At least on ILK/SNB/IVB/HSW we have the code to stop flooding dmesg
and the code to ignore the expected underruns, so I guess a patch
touching just these platforms would be ok?

> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre

--
Paulo Zanoni