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

[Jesse Barnes]

On Tue, 16 Jul 2013 22:43:49 +0200
Daniel Vetter <daniel at ffwll.ch> wrote:

> 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.

Yeah the ilk "restore to initial freq" needs fixing, but I thought we
wanted this on all gens?  It shouldn't hurt anything, and may help with
other issues as well.

-- 
Jesse Barnes, Intel Open Source Technology Center