drm/edid: Set AVI infoframe Q even when QS=0

HDMI 2.0 recommends that we set the Q bits in the AVI infoframe
even when the sink does not support quantization range selection (QS=0).
According to CEA-861 we can do that as long as the Q we send matches
the default quantization range for the mode.

Previously I think I had misread the spec as saying that you can't
send a non-zero Q at all when QS=0. But that's not what the spec
actually says.

v2: Fix typo in commit message (Jani)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170111125725.8086-5-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Acked-by: Eric Anholt <eric@anholt.net>

drivers/gpu/drm/drm_edid.c

@@ -4296,11 +4296,13 @@ EXPORT_SYMBOL(drm_hdmi_avi_infoframe_from_display_mode);
  * drm_hdmi_avi_infoframe_quant_range() - fill the HDMI AVI infoframe
  *                                        quantization range information
  * @frame: HDMI AVI infoframe
+ * @mode: DRM display mode
  * @rgb_quant_range: RGB quantization range (Q)
  * @rgb_quant_range_selectable: Sink support selectable RGB quantization range (QS)
  */
 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)
 {
@@ -4310,8 +4312,12 @@ drm_hdmi_avi_infoframe_quant_range(struct hdmi_avi_infoframe *frame,
 	 *  to the default RGB Quantization Range for the transmitted Picture
 	 *  unless the Sink indicates support for the Q bit in a Video
 	 *  Capabilities Data Block."
+	 *
+	 * HDMI 2.0 recommends sending non-zero Q when it does match the
+	 * default RGB quantization range for the mode, even when QS=0.
 	 */
-	if (rgb_quant_range_selectable)
+	if (rgb_quant_range_selectable ||
+	    rgb_quant_range == drm_default_rgb_quant_range(mode))
 		frame->quantization_range = rgb_quant_range;
 	else
 		frame->quantization_range = HDMI_QUANTIZATION_RANGE_DEFAULT;

drivers/gpu/drm/i915/intel_hdmi.c

@@ -455,17 +455,19 @@ static void intel_hdmi_set_avi_infoframe(struct drm_encoder *encoder,
 					 const struct intel_crtc_state *crtc_state)
 {
 	struct intel_hdmi *intel_hdmi = enc_to_intel_hdmi(encoder);
+	const struct drm_display_mode *adjusted_mode =
+		&crtc_state->base.adjusted_mode;
 	union hdmi_infoframe frame;
 	int ret;
 
 	ret = drm_hdmi_avi_infoframe_from_display_mode(&frame.avi,
-						       &crtc_state->base.adjusted_mode);
+						       adjusted_mode);
 	if (ret < 0) {
 		DRM_ERROR("couldn't fill AVI infoframe\n");
 		return;
 	}
 
-	drm_hdmi_avi_infoframe_quant_range(&frame.avi,
+	drm_hdmi_avi_infoframe_quant_range(&frame.avi, adjusted_mode,
 					   crtc_state->limited_color_range ?
 					   HDMI_QUANTIZATION_RANGE_LIMITED :
 					   HDMI_QUANTIZATION_RANGE_FULL,

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -356,7 +356,7 @@ static void vc4_hdmi_set_avi_infoframe(struct drm_encoder *encoder)
 		return;
 	}
 
-	drm_hdmi_avi_infoframe_quant_range(&frame.avi,
+	drm_hdmi_avi_infoframe_quant_range(&frame.avi, mode,
 					   vc4_encoder->limited_rgb_range ?
 					   HDMI_QUANTIZATION_RANGE_LIMITED :
 					   HDMI_QUANTIZATION_RANGE_FULL,

include/drm/drm_edid.h

@@ -347,6 +347,7 @@ drm_hdmi_vendor_infoframe_from_display_mode(struct hdmi_vendor_infoframe *frame,
 					    const struct drm_display_mode *mode);
 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);