On Thu, 16 Feb 2017 07:30:07 PST (-0800), 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. With this patch on top of linux-4.9 I have DPMS on/off working again, but I don't have the correct resolutions on my monitor. I just see DP1 connected 1024x768+2880+0 (normal left inverted right x axis y axis) 0mm x 0mm 1024x768 60.00* 800x600 60.32 56.25 848x480 60.00 640x480 59.94 > > 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);