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

commit 9271c0ca573e02a360b636ecd8cb408852f4e9f6 upstream.

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.

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Eric Anholt <eric@anholt.net>
Cc: Neil Kownacki <njkkow@gmail.com>
Reported-by: Neil Kownacki <njkkow@gmail.com>
Tested-by: Neil Kownacki <njkkow@gmail.com>
Fixes: fcc8a22c ("drm/edid: Set YQ bits in the AVI infoframe according to CEA-861-F")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=101639


Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171108152504.12596-1-ville.syrjala@linux.intel.com


Acked-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>