[Intel-gfx] [PATCH 3/4] drm/i915: Cache sink_count for eDP

[Dhinakaran Pandiyan]

On Mon, 2018-10-08 at 17:35 -0700, Souza, Jose wrote:
> On Mon, 2018-10-08 at 17:19 -0700, Dhinakaran Pandiyan wrote:
> > On Fri, 2018-10-05 at 16:35 -0700, José Roberto de Souza wrote:
> > > For eDP panels all the DPCD and EDID data is cached when
> > > initializing
> > > the eDP connector so in futher detection it do not call
> > > intel_dp_detect_dpcd() for eDP.
> > > The problem is on the first short pulse interruption it calls
> > > intel_dp_get_dpcd() for eDP and DP and it will read and set the
> > > sink
> > > count, causing a mismatch between old sink count and the new one
> > > triggering a full detection without needed.
> > > 
> > > Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> > > Signed-off-by: José Roberto de Souza <jose.souza at intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/intel_dp.c | 5 +++++
> > >  1 file changed, 5 insertions(+)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > > b/drivers/gpu/drm/i915/intel_dp.c
> > > index 19f0c3f59cbe..4a1c31ec9065 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -3926,6 +3926,7 @@ intel_edp_init_dpcd(struct intel_dp
> > > *intel_dp)
> > >  {
> > >  	struct drm_i915_private *dev_priv =
> > >  		to_i915(dp_to_dig_port(intel_dp)->base.base.dev);
> > > +	u8 val;
> > >  
> > >  	/* this function is meant to be called only once */
> > >  	WARN_ON(intel_dp->dpcd[DP_DPCD_REV] != 0);
> > > @@ -3997,6 +3998,10 @@ intel_edp_init_dpcd(struct intel_dp
> > > *intel_dp)
> > >  
> > >  	intel_dp_set_common_rates(intel_dp);
> > >  
> > > +	if (drm_dp_dpcd_readb(&intel_dp->aux, DP_SINK_COUNT, &val) <=
> > > 0)
> > > +		return false;
> > > +	intel_dp->sink_count = DP_GET_SINK_COUNT(val);
> > 
> > Is this even relevant for eDPs? Seems unnecessary to read or
> > compare
> > sink count for eDP. I'd suggest skipping DP_SINK_COUNT checks for
> > eDP.
> 
> I'm not sure as DP specs for DP_SINK_COUNT says:
> 
> The Sink device shall add one more if it has a local Rendering
> Function.
> 
> and eDP spec do not redefine or alter this, so I guess is more safe
> also read for eDP too.
> 

We already special case eDP in several places, for example, don't
update link rates from the short pulse handler etc. And also don't
support hotplug, I don't see a point.

-DK


> 
> > 
> > 
> > -DK
> > 
> > > +
> > >  	return true;
> > >  }
> > >