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

[Eric Anholt]

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?

That said, as far as vc4, this patch is

Acked-by: Eric Anholt <eric at anholt.net>
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