On Wed, Feb 22, 2017 at 08:00:38PM -0800, Palmer Dabbelt wrote: > On Thu, Feb 16, 2017 at 9:46 AM, Ville Syrjälä > <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > > On Thu, Feb 16, 2017 at 09:24:09AM -0800, Manasi Navare wrote: > >> On Thu, Feb 16, 2017 at 07:18:57PM +0200, Ville Syrjälä wrote: > >> > 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 > >> > >> Yes, we have parsed the DPCD but we dont write to intel_dp->link-rate and intel_dp->lane_count > >> until we do a modeset (these get written during pre_enable) and these values get used > >> during the retraining of the link. So at this point we will still use stale values. > > > > They're not stale. They're exactly what we used when we set up the > > mode that's still being drive out. This is just retraining the link > > at the same parameters. > > > >> Shouldnt we set the link status to BAD and send a hotplug event, like the solution we implemneted > >> for retraining? > >> > >> Regards > >> Manasi > >> > >> Regards > >> Manasi > > > > -- > > Ville Syrjälä > > Intel OTC > > Sorry, I forgot about this. A log is attached of my machine booting > with the monitor attached, me detaching the monitor, and then plugging > it back in. I was actually able to reproduce this yesterday with one particular kernel. It looked like it wasn't even trying to do the EDID read. Not sure why. And I wasn't able reproduce it anymore with the latest drm-tip. I should probably try to figure out what changed... -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
