linux-kernel - [PATCH v2 3/5] drm: bridge: dw_hdmi: Enable GCP only for Deep Color

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Message-Id: <a0f9def7e7438592f78ef0a16cd0a560be0e6133.1649412256.git.Sandor.yu@nxp.com>
Date:   Fri,  8 Apr 2022 18:32:26 +0800
From:   Sandor Yu <Sandor.yu@....com>
To:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        andrzej.hajda@...el.com, narmstrong@...libre.com,
        robert.foss@...aro.org, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...il.com, hverkuil-cisco@...all.nl
Cc:     Sandor.yu@....com, shengjiu.wang@....com, cai.huoqing@...ux.dev,
        maxime@...no.tech, harry.wentland@....com
Subject: [PATCH v2 3/5] drm: bridge: dw_hdmi: Enable GCP only for Deep Color

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, clear gpc_auto bit for 24-bit color depth.

Signed-off-by: Sandor Yu <Sandor.yu@....com>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 02d8f7e08814..5a7ec066e37a 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 +1164,14 @@ 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);
 
+	val = hdmi_readb(hdmi, HDMI_FC_DATAUTO3);
+	if (clear_gcp_auto == 1)
+		/* disable Auto GCP when 24-bit color */
+		val &= ~0x4;
+	else
+		val |= 0x4;
+	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);
 
-- 
2.25.1