[Intel-gfx] [PATCH] drm/i915: fix up gt init sequence fallout

[Chris Wilson]

On Sun, Jul 21, 2013 at 01:16:24PM +0200, Daniel Vetter wrote:
> The regression fix for gen6+ rps fallout
> 
> commit 7dcd2677ea912573d9ed4bcd629b0023b2d11505
> Author: Konstantin Khlebnikov <khlebnikov at openvz.org>
> Date:   Wed Jul 17 10:22:58 2013 +0400
> 
>     drm/i915: fix long-standing SNB regression in power consumption after resume
> 
> unintentionally also changed the init sequence ordering between
> gt_init and gt_reset - we need to reset BIOS damage like leftover
> forcewake references before we run our own code. Otherwise we can get
> nasty dmesg noise like
> 
> [drm:__gen6_gt_force_wake_mt_get] *ERROR* Timed out waiting for forcewake old ack to clear.
> 
> again. Since _reset suggests that we first need to have stuff
> initialized (which isn't the case here) call it sanitze instead.
> 
> While at it also block out the rps disable introduce by the above
> commit on ilk: We don't have any knowledge of ilk rps being broken in
> similar ways. And the disable functions uses the default hw state
> which is only read out when we're enabling rps. So essentially we've
> been writing random grabage into that register.
> 
> Reported-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Konstantin Khlebnikov <khlebnikov at openvz.org>
> Cc: Jesse Barnes <jbarnes at virtuousgeek.org>
> Cc: stable at vger.kernel.org
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Indeed, on ilk this does look a bit fishy.

Tested-by: Chris Wilson <chris at chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre