Re: [PATCH v3 2/4] drm: bridge: dw_hdmi: Enable GCP only for Deep Color

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On 15/04/2022 04:42, Sandor.yu@xxxxxxx wrote:
From: Sandor Yu <Sandor.yu@xxxxxxx>

HDMI1.4b specification section 6.5.3:
Source shall only send GCPs with non-zero CD to sinks
that indicate support for Deep Color.

DW HDMI GCP default enabled, but only transmit CD
and do not handle AVMUTE, PP norDefault_Phase (yet).
Disable Auto GCP when 24-bit color for sinks that not support Deep Color.

Signed-off-by: Sandor Yu <Sandor.yu@xxxxxxx>
---
  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 17 +++++++++++++++++
  drivers/gpu/drm/bridge/synopsys/dw-hdmi.h |  3 +++
  2 files changed, 20 insertions(+)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 02d8f7e08814..312500921754 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -1108,6 +1108,8 @@ static void hdmi_video_packetize(struct dw_hdmi *hdmi)
  	unsigned int output_select = HDMI_VP_CONF_OUTPUT_SELECTOR_PP;
  	struct hdmi_data_info *hdmi_data = &hdmi->hdmi_data;
  	u8 val, vp_conf;
+	u8 clear_gcp_auto = 0;
+
if (hdmi_bus_fmt_is_rgb(hdmi->hdmi_data.enc_out_bus_format) ||
  	    hdmi_bus_fmt_is_yuv444(hdmi->hdmi_data.enc_out_bus_format) ||
@@ -1117,6 +1119,7 @@ static void hdmi_video_packetize(struct dw_hdmi *hdmi)
  		case 8:
  			color_depth = 4;
  			output_select = HDMI_VP_CONF_OUTPUT_SELECTOR_BYPASS;
+			clear_gcp_auto = 1;
  			break;
  		case 10:
  			color_depth = 5;
@@ -1136,6 +1139,7 @@ static void hdmi_video_packetize(struct dw_hdmi *hdmi)
  		case 0:
  		case 8:
  			remap_size = HDMI_VP_REMAP_YCC422_16bit;
+			clear_gcp_auto = 1;
  			break;
  		case 10:
  			remap_size = HDMI_VP_REMAP_YCC422_20bit;
@@ -1160,6 +1164,19 @@ static void hdmi_video_packetize(struct dw_hdmi *hdmi)
  		HDMI_VP_PR_CD_DESIRED_PR_FACTOR_MASK);
  	hdmi_writeb(hdmi, val, HDMI_VP_PR_CD);
+ /* HDMI1.4b specification section 6.5.3:
+	 * Source shall only send GCPs with non-zero CD to sinks
+	 * that indicate support for Deep Color.
+	 * GCP only transmit CD and do not handle AVMUTE, PP norDefault_Phase (yet).
+	 * Disable Auto GCP when 24-bit color for sinks that not support Deep Color.
+	 */
+	val = hdmi_readb(hdmi, HDMI_FC_DATAUTO3);
+	if (clear_gcp_auto == 1)
+		val &= ~HDMI_FC_DATAUTO3_GCP_AUTO;
+	else
+		val |= HDMI_FC_DATAUTO3_GCP_AUTO;
+	hdmi_writeb(hdmi, val, HDMI_FC_DATAUTO3);
+
  	hdmi_modb(hdmi, HDMI_VP_STUFF_PR_STUFFING_STUFFING_MODE,
  		  HDMI_VP_STUFF_PR_STUFFING_MASK, HDMI_VP_STUFF);
diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
index 1999db05bc3b..18df3e119553 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.h
@@ -850,6 +850,9 @@ enum {
  	HDMI_FC_DATAUTO0_VSD_MASK = 0x08,
  	HDMI_FC_DATAUTO0_VSD_OFFSET = 3,
+/* FC_DATAUTO3 field values */
+	HDMI_FC_DATAUTO3_GCP_AUTO = 0x04,
+
  /* PHY_CONF0 field values */
  	HDMI_PHY_CONF0_PDZ_MASK = 0x80,
  	HDMI_PHY_CONF0_PDZ_OFFSET = 7,

Reviewed-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>



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