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

Chris Wilson
2013-09-19T20:16:07Z

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.
-Chris

--
Chris Wilson, Intel Open Source Technology Centre