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.
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