On Thu, Feb 16, 2017 at 05:30:07PM +0200, ville.syrj...@linux.intel.com wrote: > From: Ville Syrjälä <ville.syrj...@linux.intel.com> > > Apparently some DP sinks are a little nuts and cause HPD to drop > intermittently during modesets. This happens eg. on an ASUS PB287Q. > In oder to recover from this we can't really use the previous > connector status to determine if the link needs retraining, so let's > just ignore that piece of information and do the retrain > unconditionally. We do of course still check whether the link is > supposed to be running or not. > > Cc: sta...@vger.kernel.org > Cc: Palmer Dabbelt <pal...@dabbelt.com> > Reported-by: Palmer Dabbelt <pal...@dabbelt.com> > References: > https://lists.freedesktop.org/archives/intel-gfx/2017-February/119779.html > Signed-off-by: Ville Syrjälä <ville.syrj...@linux.intel.com> > --- > drivers/gpu/drm/i915/intel_dp.c | 15 +++++++++++---- > 1 file changed, 11 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c > index 024798a9c016..37a746f7fbc3 100644 > --- a/drivers/gpu/drm/i915/intel_dp.c > +++ b/drivers/gpu/drm/i915/intel_dp.c > @@ -4648,11 +4648,18 @@ intel_dp_long_pulse(struct intel_connector > *intel_connector) > */ > status = connector_status_disconnected; > goto out; > - } else if (connector->status == connector_status_connected) { > + } else { > /* > - * If display was connected already and is still connected > - * check links status, there has been known issues of > - * link loss triggerring long pulse!!!! > + * If display is now connected check links status, > + * there has been known issues of link loss triggerring > + * long pulse. > + * > + * Some sinks (eg. ASUS PB287Q) seem to perform some > + * weird HPD ping pong during modesets. So we can apparely > + * 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. > */ > drm_modeset_lock(&dev->mode_config.connection_mutex, NULL); > intel_dp_check_link_status(intel_dp); > --
So here we basically just ignore the connector status and retrain irrespectively. But that means even if we have newer values now for max link rate/lane count from DPCD, during this retrain we are just using the stale value of intel_dp->link_rate and intel_dp->lane_count. I think intel_dp->link_rate and lane count values should be set to 0 on HPD pulse, they would be set only during a modeset. Regards Manasi > 2.10.2 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
