Re: [PATCH 2/3] drm/i915/dp: Restrict link retrain workaround to external monitors

[Manasi Navare <manasi.d.navare@intel.com>]

On Fri, Sep 07, 2018 at 05:34:23PM +0300, Ville Syrjälä wrote:
> On Thu, Sep 06, 2018 at 11:21:34PM -0700, Dhinakaran Pandiyan wrote:
> > commit '3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check,
> > unconditionally during long pulse"")' applies a work around for monitors
> > that don't signal link loss. Apply this only for external displays as
> > eDP features like PSR when active will have the link turned off and the
> > driver ends up retraining the link seeeing that link is not synchronized.
> > 
> > Cc: Lyude Paul <lyude@redhat.com>
> > Cc: Jan-Marek Glogowski <glogow@fbihome.de>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> > References: 3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"")
> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> > ---
> >  drivers/gpu/drm/i915/intel_dp.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index befdaa076d8c..c59b2f78f41a 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -5072,7 +5072,9 @@ intel_dp_full_detect(struct intel_connector *connector,
> >  		 */
> >  		status = connector_status_disconnected;
> >  		goto out;
> > -	} else {
> > +	}
> > +
> > +	if (!intel_dp_is_edp(intel_dp)) {

Also what happens when the PSR is not active? We would still need to retrain
even on eDP.
eDP tends to get fixed a lot of times during link retraining.

Manasi

> 
> Hmm. How do things work if we get a short hpd from the sink while it's
> in PSR link off mode? Won't we try to retrain in that case as well?
> 
> >  		/*
> >  		 * Check link status in case the link went out of
> >  		 * synchronization and the sink did not tell us.
> > -- 
> > 2.17.1
> 
> -- 
> Ville Syrjälä
> Intel
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