Re: [PATCH] drm/i915/skl: Ensure HW is powered during DDB HW state readout

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

On ke, 2016-02-17 at 16:55 +0200, Jani Nikula wrote:
> On Wed, 17 Feb 2016, Imre Deak <imre.deak@intel.com> wrote:
> > The assumption when adding the intel_display_power_is_enabled()
> > checks
> > was that if it returns success the power can't be turned off
> > afterwards
> > during the HW access, which is guaranteed by modeset locks. This
> > isn't
> > always true, so make sure we hold a dedicated reference for the
> > time of
> > the access.
> > 
> > Spotted-by: Mika Kuoppala <mika.kuoppala@intel.com>
> > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=93441
> > CC: Chris Wilson <chris@chris-wilson.co.uk>
> > Signed-off-by: Imre Deak <imre.deak@intel.com>
> 
> Cc: fixes or stable? Fixes which commit?

Hm, yes forgot about this. We need it in -fixes since it may fix DMC
functionality according to Mika. Imo no need for it in stable, since on
other platforms it wouldn't fix anything besides HW state checking.

I pushed the "drm/i915: add missing display power refs" patchset and
this patch rebased on -fixes to
https://github.com/ideak/linux/commits/display_power_get_if_enabled-for-fixes

--Imre

> BR,
> Jani.
> 
> > ---
> >  drivers/gpu/drm/i915/intel_pm.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > b/drivers/gpu/drm/i915/intel_pm.c
> > index b63cdb2..347d4df 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -2851,7 +2851,10 @@ void skl_ddb_get_hw_state(struct
> > drm_i915_private *dev_priv,
> >  	memset(ddb, 0, sizeof(*ddb));
> >  
> >  	for_each_pipe(dev_priv, pipe) {
> > -		if (!intel_display_power_is_enabled(dev_priv,
> > POWER_DOMAIN_PIPE(pipe)))
> > +		enum intel_display_power_domain power_domain;
> > +
> > +		power_domain = POWER_DOMAIN_PIPE(pipe);
> > +		if (!intel_display_power_get_if_enabled(dev_priv,
> > power_domain))
> >  			continue;
> >  
> >  		for_each_plane(dev_priv, pipe, plane) {
> > @@ -2863,6 +2866,8 @@ void skl_ddb_get_hw_state(struct
> > drm_i915_private *dev_priv,
> >  		val = I915_READ(CUR_BUF_CFG(pipe));
> >  		skl_ddb_entry_init_from_hw(&ddb-
> > >plane[pipe][PLANE_CURSOR],
> >  					   val);
> > +
> > +		intel_display_power_put(dev_priv, power_domain);
> >  	}
> >  }
> 
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