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

[Dhinakaran Pandiyan]

On Fri, 2018-09-07 at 22:18 +0300, Ville Syrjälä wrote:
> On Fri, Sep 07, 2018 at 11:31:15AM -0700, Dhinakaran Pandiyan wrote:
> > On Fri, 2018-09-07 at 09:25 -0700, Manasi Navare wrote:
> > > 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 at redhat.com>
> > > > > Cc: Jan-Marek Glogowski <glogow at fbihome.de>
> > > > > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > > > Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
> > > > > References: 3cf71bc9904d ("drm/i915: Re-apply "Perform link
> > > > > quality check, unconditionally during long pulse"")
> > > > > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at 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?
> > > > 
> > 
> > Looks like short pulse defers retraining to ->detect(), so with
> > this
> > change we end up not retraining.
> 
> Except the ->hotplug() hook will still do the retraining I guess?
> It's a
> bit of a mess now with this getting handled in two places.
> 
Yeah, we'll have to fix shortpulse handling in a separate patch. Link
standby v/s link off also determines how we should handle short pulse
from the sink. A retrain is required if PSR put link in standby and
then it went out of sync.


> > But, we do want to retrain when we get
> > a short pulse for a bad link and the link is expected to be
> > synchronized.
> > 
> > > > >  		/*
> > > > >  		 * Check link status in case the link went
> > > > > out
> > > > > of
> > > > >  		 * synchronization and the sink did not tell
> > > > > us.
> > > > > -- 
> > > > > 2.17.1
> > > > 
> > > > -- 
> > > > Ville Syrjälä
> > > > Intel
> > > > _______________________________________________
> > > > Intel-gfx mailing list
> > > > Intel-gfx at lists.freedesktop.org
> > > > https://lists.freedesktop.org/mailman/listinfo/intel-gfx
> > > 
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> 
>