Re: [PATCH 4/4] drm/i915: make sure PC8 is enabled on suspend and disabled on resume

[Jesse Barnes <jbarnes@virtuousgeek.org>]

On Fri, 30 May 2014 16:37:53 +0300
Imre Deak <imre.deak@intel.com> wrote:

> On Thu, 2014-05-29 at 14:11 -0700, Jesse Barnes wrote:
> > From: Kristen Carlson Accardi <kristen@linux.intel.com>
> > 
> > This matches the runtime suspend paths and allows the system to enter
> > the lowest power mode at freeze time.
> > 
> > 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 | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > index b6211d7..24dc856 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.c
> > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > @@ -558,6 +558,9 @@ static int i915_drm_freeze(struct drm_device *dev)
> >  
> >  	intel_display_set_init_power(dev_priv, false);
> >  
> > +	if (IS_HASWELL(dev) || IS_BROADWELL(dev))
> > +		hsw_enable_pc8(dev_priv);
> > +
> >  	return 0;
> >  }
> >  
> > @@ -618,6 +621,9 @@ static int __i915_drm_thaw(struct drm_device *dev, bool restore_gtt_mappings)
> >  {
> >  	struct drm_i915_private *dev_priv = dev->dev_private;
> >  
> > +	if (IS_HASWELL(dev) || IS_BROADWELL(dev))
> > +		hsw_disable_pc8(dev_priv);
> 
> I would put this before we access any of the HW regs in thaw_early() and
> correspondingly the above call to hsw_enable_pc8() to suspend_late()
> before we call pci_disable_device().
> 
> With that change this is:
> Reviewed-by: Imre Deak <imre.deak@intel.com>

For the thaw side I think that makes sense.

But for the freeze side, putting it in suspend_late won't get us the
freeze behavior we want.  I think Rafael and Kristen are thinking of
re-using the freeze infrastructure for some kind of connected standby
feature, where most stuff is frozen, but the system isn't in S3 or S4,
so we need the enable_pc8 call in the _freeze path as well.

Rafael, is that correct?

I'll add a late_freeze and put it there instead, so it doesn't pollute
the S3 suspend path.

Thanks,
-- 
Jesse Barnes, Intel Open Source Technology Center