[PATCH] drm/edid: Don't send non-zero YQ in AVI infoframe for HDMI 1.x sinks

[Daniel Vetter]

On Wed, Nov 08, 2017 at 02:21:08PM -0800, Eric Anholt wrote:
> Ville Syrjälä <ville.syrjala at linux.intel.com> writes:
> 
> > On Wed, Nov 08, 2017 at 12:17:28PM -0800, Eric Anholt wrote:
> >> Ville Syrjala <ville.syrjala at linux.intel.com> writes:
> >> 
> >> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> >> >
> >> > Apparently some sinks look at the YQ bits even when receiving RGB,
> >> > and they get somehow confused when they see a non-zero YQ value.
> >> > So we can't just blindly follow CEA-861-F and set YQ to match the
> >> > RGB range.
> >> >
> >> > Unfortunately there is no good way to tell whether the sink
> >> > designer claims to have read CEA-861-F. The CEA extension block
> >> > revision number has generally been stuck at 3 since forever,
> >> > and even a very recently manufactured sink might be based on
> >> > an old design so the manufacturing date doesn't seem like
> >> > something we can use. In lieu of better information let's
> >> > follow CEA-861-F only for HDMI 2.0 sinks, since HDMI 2.0 is
> >> > based on CEA-861-F. For HDMI 1.x sinks we'll always set YQ=0.
> >> >
> >> > The alternative would of course be to always set YQ=0. And if
> >> > we ever encounter a HDMI 2.0+ sink with this bug that's what
> >> > we'll probably have to do.
> >> 
> >> Should vc4 be doing anything special for HDMI2 sinks, if it's an HDMI1.4
> >> source?
> >
> > As long as you stick to < 340 MHz modes you shouldn't have to do
> > anything. For >=340 MHz you'd need to use some new HDMI 2.0 features.
> >
> > Looks like vc4 crtc .mode_valid() doesn't do much. I presume it's up
> > to bridges/encoders to filter out most things that aren't supported?
> 
> I had a patch for that at
> https://patchwork.freedesktop.org/series/30680/ -- fedora folks had run
> into trouble with 4k monitors.

Ack on the clock limiting patch, silly that it's stuck. No idea about CEC,
better for Hans/Boris I guess.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch