On Fri, Sep 07, 2018 at 03:39:24PM +0300, Jani Nikula wrote:
> On Thu, 06 Sep 2018, Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx> wrote:
> > Comment claims link needs to be retrained because the connected sink raised
> > a long pulse to indicate link loss. If the sink did so,
> > intel_dp_hotplug() would have handled link retraining. Looking at the
> > logs in Bugzilla referenced in commit '3cf71bc9904d ("drm/i915: Re-apply
> > Perform link quality check, unconditionally during long pulse"")', the
> > issue is that the sink does not trigger an interrupt. We want the
> > ->detect() from user space to check link status and retrain. Ville's
> > review for the original patch also indicates the same root cause.
> >
> > I have also renamed long_pulse() to full_detect().
>
> Since intel_dp_detect() doesn't actually do *anything* except skip
> detect sometimes, I think "full detect" is a misnomer.
>
> Arguably you could merge intel_dp_long_pulse() into its only caller,
> intel_dp_detect(), and do an early return on skipping detect. You have
> to look at the functions, and wonder if the current split is the right
> one.
That's pretty much what I suggested earlier. Although someone should
double check to make sure the detect_done flag even makes sense these
days. Maybe it does, maybe it doesn't, I don't recall.
>
> Please let others chime in too before making changes.
>
> BR,
> Jani.
>
>
> >
> > Cc: Lyude Paul <lyude@xxxxxxxxxx>
> > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> > Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
> > Cc: Jan-Marek Glogowski <glogow@xxxxxxxxxx>
> > References: 3cf71bc9904d ("drm/i915: Re-apply "Perform link quality check, unconditionally during long pulse"")
> > Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_dp.c | 17 +++++------------
> > 1 file changed, 5 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> > index 436c22de33b6..befdaa076d8c 100644
> > --- a/drivers/gpu/drm/i915/intel_dp.c
> > +++ b/drivers/gpu/drm/i915/intel_dp.c
> > @@ -5012,7 +5012,7 @@ intel_dp_unset_edid(struct intel_dp *intel_dp)
> > }
> >
> > static int
> > -intel_dp_long_pulse(struct intel_connector *connector,
> > +intel_dp_full_detect(struct intel_connector *connector,
> > struct drm_modeset_acquire_ctx *ctx)
> > {
> > struct drm_i915_private *dev_priv = to_i915(connector->base.dev);
> > @@ -5074,16 +5074,8 @@ intel_dp_long_pulse(struct intel_connector *connector,
> > 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.
> > + * Check link status in case the link went out of
> > + * synchronization and the sink did not tell us.
> > */
> > struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
> >
> > @@ -5149,7 +5141,8 @@ intel_dp_detect(struct drm_connector *connector,
> > return ret;
> > }
> >
> > - status = intel_dp_long_pulse(intel_dp->attached_connector, ctx);
> > + status = intel_dp_full_detect(intel_dp->attached_connector,
> > + ctx);
> > }
> >
> > intel_dp->detect_done = false;
>
> --
> Jani Nikula, Intel Open Source Graphics Center
--
Ville Syrjälä
Intel
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