linux-kernel - Re: [PATCH] drm/msm/hdmi: mark interlace

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Message-ID: <52229a96-64b0-48d0-9868-31be42b12db1@quicinc.com>
Date: Fri, 1 Nov 2024 14:41:27 -0700
From: Abhinav Kumar <quic_abhinavk@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Rob Clark
	<robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten
	<marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona
 Vetter <simona@...ll.ch>
CC: <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/hdmi: mark interlace_allowed as true

On 10/18/2024 2:10 PM, Dmitry Baryshkov wrote:
> The MSM HDMI driver supports interlaced modes. Set the corresponding
> flag to allow interlaced modes on the corresponding connectors.
> 
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> ---
>   drivers/gpu/drm/msm/hdmi/hdmi_bridge.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c b/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c
> index 4a5b5112227f..643c152e6380 100644
> --- a/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c
> +++ b/drivers/gpu/drm/msm/hdmi/hdmi_bridge.c
> @@ -336,6 +336,7 @@ int msm_hdmi_bridge_init(struct hdmi *hdmi)
>   	bridge->funcs = &msm_hdmi_bridge_funcs;
>   	bridge->ddc = hdmi->i2c;
>   	bridge->type = DRM_MODE_CONNECTOR_HDMIA;
> +	bridge->interlace_allowed = true;
>   	bridge->ops = DRM_BRIDGE_OP_HPD |
>   		DRM_BRIDGE_OP_DETECT |
>   		DRM_BRIDGE_OP_EDID;
> 

I had quite a bit of discussion on this internally because this spans 
quite a few generations of chipsets.

On very old hardware, even before msm8996, there was dedicated hardware 
de-interlacer. But even on msm8996 or other HDMI supported chipsets 
where the handling of if (mode->flags & DRM_MODE_FLAG_INTERLACE) is 
present, these were because its carry forward of older interface code.

The way we handle interlaced formats today, is software needs to handle 
the part of dividing height / 2 and width * 2 and adjust the source crop 
if necessary. This part has moved to userspace for recent chips.

Othwerise, we will need to add this part in the dpu driver to adjust 
this. I am not seeing this part there yet. So may I know how you 
validated this change? Something similar to :

https://git.codelinaro.org/clo/la/kernel/msm-4.4/-/blob/caf_migration/LE.UM.1.3.r3.25/drivers/gpu/drm/msm/sde/sde_plane.c#L1340

If we add this part first to dpu code, then we can mark interlace_allowed.

> ---
> base-commit: c4f364c621d0d509190d673d80a9b23250607b4a
> change-id: 20241019-msm-hdmi-interlaced-1508c1dc9bb9
> 
> Best regards,