[Intel-gfx] [PATCH] drm/i915: fix long-standing SNB regression in power consumption after resume

[Daniel Vetter]

On Tue, Jul 16, 2013 at 01:19:25PM -0700, Jesse Barnes wrote:
> On Tue, 16 Jul 2013 10:06:54 -0700
> Jesse Barnes <jbarnes at virtuousgeek.org> wrote:
> 
> > On Tue, 16 Jul 2013 11:34:25 +0400
> > Konstantin Khlebnikov <khlebnikov at openvz.org> wrote:
> > > I've tested that patch and it really works for me. If you want change
> > > something for other hardware or
> > > extend range where forcewake is held prease do it in a separate patch.
> > > This will be good for bisecting new bugs in the future.
> > 
> > Thanks a ton for finding this Konstantin, it puts us on the right
> > track.
> > 
> > Can I ask you to test this patch?  The theory is that having RC6
> > enabled messes with the initial programming sequence, so it's probably
> > best to just shut it off at init until we're done, rather than trying
> > to forcewake around everywhere we need it.
> 
> Oops, last one triggers a warn about IRQs.  This one doesn't and still
> works for me.
> 
> Testing welcome.
> 
> Thanks,
> -- 
> Jesse Barnes, Intel Open Source Technology Center
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index c9d9d20..d962ec0 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -4112,6 +4112,9 @@ i915_gem_init_hw(struct drm_device *dev)
>         drm_i915_private_t *dev_priv = dev->dev_private;
>         int ret;
>  
> +       /* BIOS often leaves RC6 enabled, but disable it for hw init */
> +       intel_disable_gt_powersave(dev);

I think it'd be better to have an explicit gen >= 6 check here and a
disable_rps call. disable_gt_powersave also calls the ironlake version,
which restores probably bogus values (since we haven't read them out yet
in the enable code) into the hw.
-Daniel

> +
>         if (INTEL_INFO(dev)->gen < 6 && !intel_enable_gtt())
>                 return -EIO;
>  
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch