On Thu, Feb 16, 2017 at 09:07:53AM -0800, Manasi Navare wrote: > On Thu, Feb 16, 2017 at 05:30:07PM +0200, ville.syrjala@xxxxxxxxxxxxxxx wrote: > > From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > > > 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: stable@xxxxxxxxxxxxxxx > > Cc: Palmer Dabbelt <palmer@xxxxxxxxxxx> > > Reported-by: Palmer Dabbelt <palmer@xxxxxxxxxxx> > > References: https://lists.freedesktop.org/archives/intel-gfx/2017-February/119779.html > > Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > > --- > > 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. We ignore the _previous_ connector status. > 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. The DPCD has already been parsed by this time. -- Ville Syrjälä Intel OTC