[PATCH v2 4/7] drm/connector: hdmi: Use YUV420 output format as an RGB fallback

[Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>]

Try to make use of YUV420 when computing the best output format and
RGB cannot be supported for any of the available color depths.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@xxxxxxxxxxxxx>
---
 drivers/gpu/drm/display/drm_hdmi_state_helper.c | 69 +++++++++++++------------
 1 file changed, 35 insertions(+), 34 deletions(-)

diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
index a70e204a8df3ac1c2d7318e81cde87a83267dd21..f2052781b797dd09b41127e33d98fe25408a9b23 100644
--- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
+++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
@@ -287,8 +287,9 @@ hdmi_try_format_bpc(const struct drm_connector *connector,
 	struct drm_device *dev = connector->dev;
 	int ret;
 
-	drm_dbg_kms(dev, "Trying %s output format\n",
-		    drm_hdmi_connector_get_output_format_name(fmt));
+	drm_dbg_kms(dev, "Trying %s output format with %u bpc\n",
+		    drm_hdmi_connector_get_output_format_name(fmt),
+		    bpc);
 
 	if (!sink_supports_format_bpc(connector, info, mode, fmt, bpc)) {
 		drm_dbg_kms(dev, "%s output format not supported with %u bpc\n",
@@ -313,47 +314,22 @@ hdmi_try_format_bpc(const struct drm_connector *connector,
 }
 
 static int
-hdmi_compute_format(const struct drm_connector *connector,
-		    struct drm_connector_state *conn_state,
-		    const struct drm_display_mode *mode,
-		    unsigned int bpc)
-{
-	struct drm_device *dev = connector->dev;
-
-	/*
-	 * TODO: Add support for YCbCr420 output for HDMI 2.0 capable
-	 * devices, for modes that only support YCbCr420.
-	 */
-	if (hdmi_try_format_bpc(connector, conn_state, mode, bpc, HDMI_COLORSPACE_RGB)) {
-		conn_state->hdmi.output_format = HDMI_COLORSPACE_RGB;
-		return 0;
-	}
-
-	drm_dbg_kms(dev, "Failed. No Format Supported for that bpc count.\n");
-
-	return -EINVAL;
-}
-
-static int
-hdmi_compute_config(const struct drm_connector *connector,
-		    struct drm_connector_state *conn_state,
-		    const struct drm_display_mode *mode)
+hdmi_try_format(const struct drm_connector *connector,
+		struct drm_connector_state *conn_state,
+		const struct drm_display_mode *mode,
+		unsigned int max_bpc, enum hdmi_colorspace fmt)
 {
 	struct drm_device *dev = connector->dev;
-	unsigned int max_bpc = clamp_t(unsigned int,
-				       conn_state->max_bpc,
-				       8, connector->max_bpc);
 	unsigned int bpc;
 	int ret;
 
 	for (bpc = max_bpc; bpc >= 8; bpc -= 2) {
-		drm_dbg_kms(dev, "Trying with a %d bpc output\n", bpc);
-
-		ret = hdmi_compute_format(connector, conn_state, mode, bpc);
-		if (ret)
+		ret = hdmi_try_format_bpc(connector, conn_state, mode, bpc, fmt);
+		if (!ret)
 			continue;
 
 		conn_state->hdmi.output_bpc = bpc;
+		conn_state->hdmi.output_format = fmt;
 
 		drm_dbg_kms(dev,
 			    "Mode %ux%u @ %uHz: Found configuration: bpc: %u, fmt: %s, clock: %llu\n",
@@ -368,6 +344,31 @@ hdmi_compute_config(const struct drm_connector *connector,
 	return -EINVAL;
 }
 
+static int
+hdmi_compute_config(const struct drm_connector *connector,
+		    struct drm_connector_state *conn_state,
+		    const struct drm_display_mode *mode)
+{
+	unsigned int max_bpc = clamp_t(unsigned int,
+				       conn_state->max_bpc,
+				       8, connector->max_bpc);
+	int ret;
+
+	ret = hdmi_try_format(connector, conn_state, mode, max_bpc,
+			      HDMI_COLORSPACE_RGB);
+	if (!ret)
+		return 0;
+
+	if (connector->ycbcr_420_allowed)
+		ret = hdmi_try_format(connector, conn_state, mode, max_bpc,
+				      HDMI_COLORSPACE_YUV420);
+	else
+		drm_dbg_kms(connector->dev,
+			    "%s output format not allowed for connector\n",
+			    drm_hdmi_connector_get_output_format_name(HDMI_COLORSPACE_YUV420));
+	return ret;
+}
+
 static int hdmi_generate_avi_infoframe(const struct drm_connector *connector,
 				       struct drm_connector_state *conn_state)
 {

-- 
2.48.1