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. Dave. _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/intel-gfx
