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

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