Re: [PATCH] drm/i915: leave rc6 enabled at suspend time v4

[Imre Deak <imre.deak@intel.com>]

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On Tue, 2014-06-10 at 15:57 +0200, Daniel Vetter wrote:
> On Tue, Jun 10, 2014 at 04:42:50PM +0300, Imre Deak wrote:
> > On Wed, 2014-06-04 at 13:45 -0700, Jesse Barnes wrote:
> > > This allows the system to enter the lowest power mode during system freeze.
> > > 
> > > v2: delete force wake timer at suspend (Imre)
> > > v3: add GT work suspend function (Imre)
> > > v4: use uncore forcewake reset (Daniel)
> > > 
> > > Signed-off-by: Kristen Carlson Accardi <kristen@linux.intel.com>
> > > Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.c     |  4 ++--
> > >  drivers/gpu/drm/i915/i915_drv.h     |  1 +
> > >  drivers/gpu/drm/i915/intel_drv.h    |  1 +
> > >  drivers/gpu/drm/i915/intel_pm.c     | 20 ++++++++++++++++++++
> > >  drivers/gpu/drm/i915/intel_uncore.c |  2 +-
> > >  5 files changed, 25 insertions(+), 3 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > > index 66c6ffb..7148eac 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > @@ -521,7 +521,7 @@ static int i915_drm_freeze(struct drm_device *dev)
> > >  		drm_irq_uninstall(dev);
> > >  		dev_priv->enable_hotplug_processing = false;
> > >  
> > > -		intel_disable_gt_powersave(dev);
> > > +		intel_suspend_gt_powersave(dev);
> > 
> > I realized now that we actually do need to enable RC6 explicitly. If we
> > get here right after runtime resume, the deferred RC6 enabling might be
> > still pending and so RC6 might not be enabled.
> 
> Hm, for runtime pm we might schedule the delayed rps work with a 0 delay,
> just to get the gpu going faster. Just an aside.
>
> Also some runtime pm vs system suspend tests in igt would be good if we
> don't have them yet. And if we have them some analysis why this didn't
> blow up in testing (and something to address that gap if feasible).

To clarify the above is about the new functionality to enable deeper
system wide power states. Atm, we don't have a bug related to the above
runtime resume->system suspend sequence, since we explicitly disable gt
power saving/RC6. For deeper power states we have to do the opposite and
leave RC6 enabled and that's what I commented on.

--Imre 


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