On Thu, 01 Jun 2017, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: > On Thu, Jun 01, 2017 at 03:55:13PM +0300, Jani Nikula wrote: >> On Wed, 31 May 2017, Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> wrote: >> > On Wed, May 31, 2017 at 08:05:35PM +0300, Imre Deak wrote: >> >> Atm disabling either DP or eDP outputs can generate a spurious short >> >> pulse interrupt. The reason is that after disabling the port the source >> >> will stop sending a valid stream data, while the sink expects either a >> >> valid stream or the idle pattern. Since neither of this is sent the sink >> >> assumes (after an arbitrary delay) that the link is lost and requests >> >> for link retraining with a short pulse. >> >> >> >> The spurious pulse is a real problem at least for eDP panels with long >> >> power-off / power-cycle delays: as part of disabling the output we >> >> disable the panel power. The subsequent spurious short pulse handling >> >> will have to turn the power back on, which means the driver has to do a >> >> redundant wait for the power-off and power-cycle delays. During system >> >> suspend this leads to an unnecessary delay up to ~1s on systems with >> >> such panels as reported by Rui. >> >> >> >> To fix this put the sink to DPMS D3 state before turning off the port. >> >> According to the DP spec in this state the sink should not request >> >> retraining. This is also what we do already on pre-ddi platforms. >> >> >> >> As an alternative I also tried configuring the port to send idle pattern >> >> - which is against BSPec - and leave the port in normal mode before >> >> turning off the port. Neither of these resolved the problem. >> >> >> >> Cc: Zhang Rui <rui.zhang@xxxxxxxxx> >> >> Cc: David Weinehall <david.weinehall@xxxxxxxxxxxxxxx> >> >> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> >> >> Reported-and-tested-by: Zhang Rui <rui.zhang@xxxxxxxxx> >> >> Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx> >> > >> > Makes sense to me. >> >> I wonder if we should write D0 on hotplug. > > D0 is the default power state IIRC, so when you plug something in it > should automagically go into D0. That's actually a slight problem > power-wise if there's no subsequent modeset to drop it into D3. Right. The thought was about branch devices that don't wake up and aren't disconnected/reconnected after D3. But then we don't receive HPD for them aither. BR, Jani. -- Jani Nikula, Intel Open Source Technology Center _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
