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

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Message-ID: <e38e8450-94c5-90f6-207e-07af972f3ed0@baylibre.com>
Date:   Fri, 15 Apr 2022 09:08:58 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Sandor.yu@....com, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org, andrzej.hajda@...el.com,
        robert.foss@...aro.org, Laurent.pinchart@...asonboard.com,
        jonas@...boo.se, jernej.skrabec@...il.com, hverkuil-cisco@...all.nl
Cc:     shengjiu.wang@....com, cai.huoqing@...ux.dev, maxime@...no.tech,
        harry.wentland@....com
Subject: Re: [PATCH v3 2/4] drm: bridge: dw_hdmi: Enable GCP only for Deep
 Color

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