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

[Daniel Vetter]

On Tue, Aug 13, 2013 at 11:55:17AM -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 125000 instead of 50000 seems to fix
> the issue. The previous patch used 150000 but as it turns out
> this doesn't work everywhere. After getting such a machine, I
> bisected the highest value which works, which is 125000, so here
> it is.
> 
> I also measured the idle power usage before/after this patch and
> didn't see a difference on a sandy bridge laptop. On haswell and
> up, it makes a big difference, so we want to keep it at 50k
> there. It also seems like haswell doesn't have the RC6 issues
> that sandy bridge has so the 50k value is fine.
> 
> Signed-off-by: Stéphane Marchesin <marcheu at chromium.org>
Queued for -next, thanks for the patch.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch