Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <25ca3826-44ee-ca6f-fb6b-1ef62f6da456@baylibre.com>
Date:   Fri, 8 Apr 2022 14:40:23 +0200
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101
 Thunderbird/91.5.0
Subject: Re: [PATCH v2 3/5] drm: bridge: dw_hdmi: Enable GCP only for Deep
 Color
Content-Language: en-US
To:     Sandor Yu <Sandor.yu@nxp.com>, dri-devel@lists.freedesktop.org,
        linux-kernel@vger.kernel.org, andrzej.hajda@intel.com,
        robert.foss@linaro.org, Laurent.pinchart@ideasonboard.com,
        jonas@kwiboo.se, jernej.skrabec@gmail.com, hverkuil-cisco@xs4all.nl
Cc:     shengjiu.wang@nxp.com, cai.huoqing@linux.dev, maxime@cerno.tech,
        harry.wentland@amd.com
References: <cover.1649412256.git.Sandor.yu@nxp.com>
 <a0f9def7e7438592f78ef0a16cd0a560be0e6133.1649412256.git.Sandor.yu@nxp.com>
From:   Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
In-Reply-To: <a0f9def7e7438592f78ef0a16cd0a560be0e6133.1649412256.git.Sandor.yu@nxp.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 08/04/2022 12:32, Sandor Yu wrote:
> 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.

It's right because we do not handle AVMUTE, Pixel Packing nor Default_Phase.

> 
> Signed-off-by: Sandor Yu <Sandor.yu@nxp.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 */

Maybe add a new define for HDMI_FC_DATAUTO3_GCP_AUTO bit and use it here.

> +		val &= ~0x4;
> +	else
> +		val |= 0x4;
> +	hdmi_writeb(hdmi, val, HDMI_FC_DATAUTO3);

Please also add a comment explaining we clear GCP because we only
transmit CD and do not handle AVMUTE, PP nor Default_Phase (yet).

> +
>   	hdmi_modb(hdmi, HDMI_VP_STUFF_PR_STUFFING_STUFFING_MODE,
>   		  HDMI_VP_STUFF_PR_STUFFING_MASK, HDMI_VP_STUFF);
>   

Thanks,
Neil