[Intel-gfx] [PATCH 1/2] drm/i915: tune the RC6 threshold for stability

[Stéphane Marchesin]

On Wed, Jun 12, 2013 at 2:41 AM, Chris Wilson <chris at chris-wilson.co.uk> wrote:
> On Tue, Jun 11, 2013 at 03:49:26PM -0700, Stéphane Marchesin wrote:
>> It's basically the same deal as the RC6+ issues on ivy bridge
>> except this time with RC6 on sandy bridge. Like last time the
>> core of the issue is that the timings don't work 100% with our
>> voltage regulator. So from time to time, the kernel will print
>> a warning message about the GPU not getting out of RC6. In
>> particular, I found this fairly easy to reproduce during
>> suspend/resume.
>>
>> Changing the threshold to 150000 instead of 50000 seems to fix
>> the issue.
>>
>> I also measured the idle power usage before/after this patch and
>> didn't see a difference on a sandy bridge laptop.
>>
>> Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
>
> One magic number for another with no idea what is blowing up - I fear we
> are just changing the frequency of the hang. I've pinged a number of snb
> rc6 bug reports to see if we get a bite.

Yup, if only Intel documented those registers :)

Stéphane

>
> FWIW,
> Acked-by: Chris Wilson <chris at chris-wilson.co.uk>
> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre