| Message ID | 20180924224528.4744-1-dhinakaran.pandiyan@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,1/6] drm/i915/dp: Fix link retraining comment in intel_dp_long_pulse() | expand |
Reviewed-by: Lyude Paul <lyude@redhat.com> On Mon, 2018-09-24 at 15:45 -0700, Dhinakaran Pandiyan 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. What we want is > ->detect() from user space to check link status and retrain. Ville's > review for the original patch also indicates the same root cause. So, > rewrite the comment. > > v2: Patch split and rewrote comment. > > Cc: Lyude Paul <lyude@redhat.com> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> > Cc: Jani Nikula <jani.nikula@linux.intel.com> > Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> > Cc: Jan-Marek Glogowski <glogow@fbihome.de> > 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 | 13 +++---------- > 1 file changed, 3 insertions(+), 10 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_dp.c > b/drivers/gpu/drm/i915/intel_dp.c > index 6b4c19123f2a..34c561011e7a 100644 > --- a/drivers/gpu/drm/i915/intel_dp.c > +++ b/drivers/gpu/drm/i915/intel_dp.c > @@ -5074,16 +5074,9 @@ 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. > + * Some external monitors do not signal loss of link > + * synchronization with an IRQ_HPD, so force a link status > + * check. > */ > struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)- > >base; >
diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c index 6b4c19123f2a..34c561011e7a 100644 --- a/drivers/gpu/drm/i915/intel_dp.c +++ b/drivers/gpu/drm/i915/intel_dp.c @@ -5074,16 +5074,9 @@ 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. + * Some external monitors do not signal loss of link + * synchronization with an IRQ_HPD, so force a link status + * check. */ struct intel_encoder *encoder = &dp_to_dig_port(intel_dp)->base;
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. What we want is ->detect() from user space to check link status and retrain. Ville's review for the original patch also indicates the same root cause. So, rewrite the comment. v2: Patch split and rewrote comment. Cc: Lyude Paul <lyude@redhat.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Jani Nikula <jani.nikula@linux.intel.com> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com> Cc: Jan-Marek Glogowski <glogow@fbihome.de> 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 | 13 +++---------- 1 file changed, 3 insertions(+), 10 deletions(-)