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

[Ville Syrjala]

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.

Cc: stable at vger.kernel.org
Cc: Jani Nikula <jani.nikula at intel.com>
Cc: Eric Anholt <eric at anholt.net>
Cc: Neil Kownacki <njkkow at gmail.com>
Reported-by: Neil Kownacki <njkkow at gmail.com>
Fixes: fcc8a22cc905 ("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 at linux.intel.com>
---
 drivers/gpu/drm/drm_edid.c        | 12 ++++++++++--
 drivers/gpu/drm/i915/intel_hdmi.c |  3 ++-
 drivers/gpu/drm/vc4/vc4_hdmi.c    |  3 ++-
 include/drm/drm_edid.h            |  3 ++-
 4 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index 749d07a01772..8567890f47a7 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -4838,7 +4838,8 @@ void
 drm_hdmi_avi_infoframe_quant_range(struct hdmi_avi_infoframe *frame,
 				   const struct drm_display_mode *mode,
 				   enum hdmi_quantization_range rgb_quant_range,
-				   bool rgb_quant_range_selectable)
+				   bool rgb_quant_range_selectable,
+				   bool is_hdmi2_sink)
 {
 	/*
 	 * CEA-861:
@@ -4862,8 +4863,15 @@ drm_hdmi_avi_infoframe_quant_range(struct hdmi_avi_infoframe *frame,
 	 *  YQ-field to match the RGB Quantization Range being transmitted
 	 *  (e.g., when Limited Range RGB, set YQ=0 or when Full Range RGB,
 	 *  set YQ=1) and the Sink shall ignore the YQ-field."
+	 *
+	 * Unfortunate certain sinks (eg. VIZ Model 67/E261VA) get confused
+	 * by non-zero YQ when receiving RGB. There doesn't seem to be any
+	 * good way to tell which version of CEA-861 the sink supports, so
+	 * we limit non-zero YQ to HDMI 2.0 sinks only as HDMI 2.0 is based
+	 * on on CEA-861-F.
 	 */
-	if (rgb_quant_range == HDMI_QUANTIZATION_RANGE_LIMITED)
+	if (!is_hdmi2_sink ||
+	    rgb_quant_range == HDMI_QUANTIZATION_RANGE_LIMITED)
 		frame->ycc_quantization_range =
 			HDMI_YCC_QUANTIZATION_RANGE_LIMITED;
 	else
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c b/drivers/gpu/drm/i915/intel_hdmi.c
index fa1c793a21ef..2b23d3662eec 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -487,7 +487,8 @@ static void intel_hdmi_set_avi_infoframe(struct drm_encoder *encoder,
 					   crtc_state->limited_color_range ?
 					   HDMI_QUANTIZATION_RANGE_LIMITED :
 					   HDMI_QUANTIZATION_RANGE_FULL,
-					   intel_hdmi->rgb_quant_range_selectable);
+					   intel_hdmi->rgb_quant_range_selectable,
+					   is_hdmi2_sink);
 
 	/* TODO: handle pixel repetition for YCBCR420 outputs */
 	intel_write_infoframe(encoder, crtc_state, &frame);
diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 9a9a6b4acccf..d645df0c6d15 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -423,7 +423,8 @@ static void vc4_hdmi_set_avi_infoframe(struct drm_encoder *encoder)
 					   vc4_encoder->limited_rgb_range ?
 					   HDMI_QUANTIZATION_RANGE_LIMITED :
 					   HDMI_QUANTIZATION_RANGE_FULL,
-					   vc4_encoder->rgb_range_selectable);
+					   vc4_encoder->rgb_range_selectable,
+					   false);
 
 	vc4_hdmi_write_infoframe(encoder, &frame);
 }
diff --git a/include/drm/drm_edid.h b/include/drm/drm_edid.h
index 9e4e23524840..58ffb68efdc5 100644
--- a/include/drm/drm_edid.h
+++ b/include/drm/drm_edid.h
@@ -361,7 +361,8 @@ void
 drm_hdmi_avi_infoframe_quant_range(struct hdmi_avi_infoframe *frame,
 				   const struct drm_display_mode *mode,
 				   enum hdmi_quantization_range rgb_quant_range,
-				   bool rgb_quant_range_selectable);
+				   bool rgb_quant_range_selectable,
+				   bool is_hdmi2_sink);
 
 /**
  * drm_eld_mnl - Get ELD monitor name length in bytes.
-- 
2.13.6