[PATCH 2/3] drm/connector: hdmi: Add support for YUV420 format verification

[Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>]

Provide the necessary constraints verification in
sink_supports_format_bpc() in order to support handling of YUV420
output format.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/display/drm_hdmi_state_helper.c | 40 +++++++++++++++++++++++--
 1 file changed, 37 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index 0cbcee7e77cd8dff387044487ce28ee5748f5587..3a55881a544a519bb1254968db891c814f831a0f 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -3,6 +3,7 @@
 #include <drm/drm_atomic.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_edid.h>
+#include <drm/drm_modes.h>
 #include <drm/drm_print.h>
 
 #include <drm/display/drm_hdmi_helper.h>
@@ -114,6 +115,12 @@ sink_supports_format_bpc(const struct drm_connector *connector,
 		return false;
 	}
 
+	if (drm_mode_is_420_only(info, mode) && format != HDMI_COLORSPACE_YUV420) {
+		drm_dbg_kms(dev, "%s format unsupported by the sink for VIC%u.\n",
+			    drm_hdmi_connector_get_output_format_name(format), vic);
+		return false;
+	}
+
 	switch (format) {
 	case HDMI_COLORSPACE_RGB:
 		drm_dbg_kms(dev, "RGB Format, checking the constraints.\n");
@@ -144,9 +151,36 @@ sink_supports_format_bpc(const struct drm_connector *connector,
 		return true;
 
 	case HDMI_COLORSPACE_YUV420:
-		/* TODO: YUV420 is unsupported at the moment. */
-		drm_dbg_kms(dev, "YUV420 format isn't supported yet.\n");
-		return false;
+		drm_dbg_kms(dev, "YUV420 format, checking the constraints.\n");
+
+		if (!(info->color_formats & DRM_COLOR_FORMAT_YCBCR420)) {
+			drm_dbg_kms(dev, "Sink doesn't support YUV420.\n");
+			return false;
+		}
+
+		if (!drm_mode_is_420(info, mode)) {
+			drm_dbg_kms(dev, "Sink doesn't support YUV420 for VIC%u.\n", vic);
+			return false;
+		}
+
+		if (bpc == 10 && !(info->hdmi.y420_dc_modes & DRM_EDID_YCBCR420_DC_30)) {
+			drm_dbg_kms(dev, "10 BPC but sink doesn't support Deep Color 30.\n");
+			return false;
+		}
+
+		if (bpc == 12 && !(info->hdmi.y420_dc_modes & DRM_EDID_YCBCR420_DC_36)) {
+			drm_dbg_kms(dev, "12 BPC but sink doesn't support Deep Color 36.\n");
+			return false;
+		}
+
+		if (bpc == 16 && !(info->hdmi.y420_dc_modes & DRM_EDID_YCBCR420_DC_48)) {
+			drm_dbg_kms(dev, "16 BPC but sink doesn't support Deep Color 48.\n");
+			return false;
+		}
+
+		drm_dbg_kms(dev, "YUV420 format supported in that configuration.\n");
+
+		return true;
 
 	case HDMI_COLORSPACE_YUV422:
 		drm_dbg_kms(dev, "YUV422 format, checking the constraints.\n");

-- 
2.47.0