Re: [PATCH] v3 drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"

[Lyude Paul <lyude@redhat.com>]

On Fri, 2018-08-17 at 13:12 +0200, Jan-Marek Glogowski wrote:
> Resend, as this was in my sent-mail folder, but it doesn't appear in the list
> archive…
> 
> Am August 16, 2018 6:03:50 PM UTC schrieb Manasi Navare <
> manasi.d.navare@intel.com>:
> > On Wed, Aug 08, 2018 at 10:53:35AM +0200, Jan-Marek Glogowski wrote:
> > > This re-applies the workaround for "some DP sinks, [which] are a
> > > little nuts" from commit 1a36147bb939 ("drm/i915: Perform link
> > > quality check unconditionally during long pulse").
> > > It makes the secondary AOC E2460P monitor connected via DP to an
> > > acer Veriton N4640G usable again.
> > 
> > Would be nice to add in the commit message that this sink sends a
> > long pulse to indicate link loss, hence check link status during long
> > pulse.
> 
> I have no idea, if this is happening. I just found the monitor wasn't working
> with the current
> kernel, when I was trying to debug an other bug I ran into while backporting
> DRM 4.15 to 4.4. I did
> a bisect while at it. Please read the FDO bug for more info.
I think you misunderstood-I believe mdnavare was asking if you could put the
comment that was on 1a36147bb939 originally in your patch

> 
> > If there is a FDO bug associated with this you could also add the
> > Bugzilla link before Sign off tag.
> > But other than that this looks good to me.
> 
> FDO bug: https://bugs.freedesktop.org/show_bug.cgi?id=107446
> 
> Jan-Marek
> 
> > 
> > Manasi
> > 
> > > 
> > > This hunk was dropped in commit c85d200e8321 ("drm/i915: Move SST
> > > DP link retraining into the ->post_hotplug() hook")
> > > 
> > > Signed-off-by: Jan-Marek Glogowski <glogow@fbihome.de>
> > > ---
> > >  drivers/gpu/drm/i915/intel_dp.c | 33
> > 
> > +++++++++++++++++++--------------
> > >  1 file changed, 19 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/intel_dp.c
> > 
> > b/drivers/gpu/drm/i915/intel_dp.c
> > > index 8e0e14b..22b2452 100644
> > > --- a/drivers/gpu/drm/i915/intel_dp.c
> > > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > > @@ -4333,18 +4333,6 @@ intel_dp_needs_link_retrain(struct intel_dp
> > 
> > *intel_dp)
> > >  	return !drm_dp_channel_eq_ok(link_status, intel_dp->lane_count);
> > >  }
> > > 
> > > -/*
> > > - * If display is now connected check links status,
> > > - * there has been known issues of link loss triggering
> > > - * long pulse.
> > > - *
> > > - * Some sinks (eg. ASUS PB287Q) seem to perform some
> > > - * weird HPD ping pong during modesets. So we can apparently
> > > - * end up with HPD going low during a modeset, and then
> > > - * going back up soon after. And once that happens we must
> > > - * retrain the link to get a picture. That's in case no
> > > - * userspace component reacted to intermittent HPD dip.
> > > - */
> > >  int intel_dp_retrain_link(struct intel_encoder *encoder,
> > >  			  struct drm_modeset_acquire_ctx *ctx)
> > >  {
> > > @@ -4923,7 +4911,8 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
> > >  }
> > > 
> > >  static int
> > > -intel_dp_long_pulse(struct intel_connector *connector)
> > > +intel_dp_long_pulse(struct intel_connector *connector,
> > > +		    struct drm_modeset_acquire_ctx *ctx)
> > >  {
> > >  	struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> > >  	struct intel_dp *intel_dp = intel_attached_dp(&connector->base);
> > > @@ -4982,6 +4971,22 @@ intel_dp_long_pulse(struct intel_connector
> > 
> > *connector)
> > >  		 */
> > >  		status = connector_status_disconnected;
> > >  		goto out;
> > > +	} else {
> > > +		/*
> > > +		 * If display is now connected check links status,
> > > +		 * there has been known issues of link loss triggering
> > > +		 * long pulse.
> > > +		 *
> > > +		 * Some sinks (eg. ASUS PB287Q) seem to perform some
> > > +		 * weird HPD ping pong during modesets. So we can apparently
> > > +		 * end up with HPD going low during a modeset, and then
> > > +		 * going back up soon after. And once that happens we must
> > > +		 * retrain the link to get a picture. That's in case no
> > > +		 * userspace component reacted to intermittent HPD dip.
> > > +		 */
> > > +		struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
> > > +
> > > +		intel_dp_retrain_link(encoder, ctx);
> > >  	}
> > > 
> > >  	/*
> > > @@ -5043,7 +5048,7 @@ intel_dp_detect(struct drm_connector
> > 
> > *connector,
> > >  				return ret;
> > >  		}
> > > 
> > > -		status = intel_dp_long_pulse(intel_dp->attached_connector);
> > > +		status = intel_dp_long_pulse(intel_dp->attached_connector, ctx);
> > >  	}
> > > 
> > >  	intel_dp->detect_done = false;
> > > -- 
> > > 2.1.4
> > > 
> 
> 

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