On Wed, 18 Nov 2015 22:30:32 +0100, Dave Airlie wrote: > > On 19 November 2015 at 02:00, Takashi Iwai <tiwai@xxxxxxx> wrote: > > On Wed, 18 Nov 2015 16:38:03 +0100, > > Ville Syrjälä wrote: > >> > >> On Wed, Nov 18, 2015 at 04:23:06PM +0100, Takashi Iwai wrote: > >> > Hi, > >> > > >> > currently a DDI port may register both DP and HDMI and it shares the > >> > same encoder. The bug we've got a report is about this encoder type: > >> > namely, a machine using DDI port D for HDMI is screwed up because the > >> > encoder is switched to DP suddently. The details are found in: > >> > http://bugzilla.opensuse.org/show_bug.cgi?id=955190 > >> > > >> > The problem happens in intel_dp_hpd_pulse(). Since the machine > >> > declares both DP and HDMI, the driver registers this callback. And at > >> > a hotplug event, the function changes the encoder type like: > >> > > >> > if (intel_dig_port->base.type != INTEL_OUTPUT_EDP) > >> > intel_dig_port->base.type = INTEL_OUTPUT_DISPLAYPORT; > >> > > >> > After this point, the encoder is handled as DP although the same HDMI > >> > monitor is connected. > >> > > >> > Changing this to exclude INTEL_OUTPUT_HDMI makes the thing working in > >> > the bug report above, but I'm not sure what's the right fix. > >> > > >> > Any suggestions? > >> > >> This has been causing all sorts of troubles for years. I've suggested > >> several times that we should just split the encoder into two, like we > >> have for older platforms, but no one has taken the bait thus far. > >> > >> This particular piece of code to change the encoder type in the > >> hpd_pulse hook came about with the mst code drop from Dave IIRC. At > >> least I never figured out what it's trying to do since -ENOCOMMENT. > > > > Yeah, this was introduced in the commit > > > > 0e32b39ceed665bfa4a77a4bc307b6652b991632 > > drm/i915: add DP 1.2 MST support (v0.7) > > > > so the problem exists for quite some time, since 3.17 kernel. > > > > I guess the patch just overlooked the DDI use case with HDMI. > > Maybe the code was meant like below? > > > > if (intel_dig_port->base.type == INTEL_OUTPUT_UNKNOWN || > > intel_dig_port->base.type == INTEL_OUTPUT_DP_MST) > > intel_dig_port->base.type = INTEL_OUTPUT_DISPLAYPORT; > > > > That code was copied from intel_dp_detect, which does that check. > > But if the HDMI hdp is going via that path then yes it should check > more than EDP. OK, so we'd just need to add the check of INTEL_OUTPUT_HDMI in each place, as a quick fix? Since this bug has been present for a long time (since 3.17), I'd love to have a quick fix that is applicable to stable kernels, at first. thanks, Takashi _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
