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Message-ID: <203a2b93-a842-8cf2-b265-864f520c16a6@baylibre.com>
Date:   Wed, 6 Apr 2022 11:20:16 +0200
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Subject: Re: [PATCH v1 3/5] drm: bridge: dw_hdmi: Enable GCP only for Deep
 Color
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To:     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
Cc:     shengjiu.wang@nxp.com, cai.huoqing@linux.dev, maxime@cerno.tech,
        harry.wentland@amd.com, hverkuil-cisco@xs4all.nl,
        amuel@sholland.org
References: <cover.1649230434.git.Sandor.yu@nxp.com>
 <ebd9830fe35d79153cb0051bed0d255fb004fb63.1649230434.git.Sandor.yu@nxp.com>
From:   Neil Armstrong <narmstrong@baylibre.com>
Organization: Baylibre
In-Reply-To: <ebd9830fe35d79153cb0051bed0d255fb004fb63.1649230434.git.Sandor.yu@nxp.com>
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On 06/04/2022 10:48, Sandor.yu@nxp.com wrote:
> From: Sandor Yu <Sandor.yu@nxp.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 GPC default enabled, clear gpc_auto bit for bpp 24.
> 
> Signed-off-by: Sandor Yu <Sandor.yu@nxp.com>
> ---
>   drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index b11577de4836..c7b11582529e 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -1160,6 +1160,14 @@ 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 (color_depth == 4)
> +		/* disable Auto GCP when bpp 24 */
> +		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);
>   

Do you handle the case when color_depth == 0 when output is YUV422 ?

Neil