linux-kernel - Re: [PATCH v12 13/14] drm/mediatek: dpi: Only enable dpi after the bridge is enabled

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Date:   Tue, 21 Jun 2022 11:18:26 +0800
From:   CK Hu <ck.hu@...iatek.com>
To:     Bo-Chen Chen <rex-bc.chen@...iatek.com>, <chunkuang.hu@...nel.org>,
        <p.zabel@...gutronix.de>, <daniel@...ll.ch>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <matthias.bgg@...il.com>,
        <airlied@...ux.ie>
CC:     <msp@...libre.com>, <granquet@...libre.com>,
        <jitao.shi@...iatek.com>, <wenst@...omium.org>,
        <angelogioacchino.delregno@...labora.com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <Project_Global_Chrome_Upstream_Group@...iatek.com>
Subject: Re: [PATCH v12 13/14] drm/mediatek: dpi: Only enable dpi after the
 bridge is enabled

Hi, Bo-Chen:

On Mon, 2022-06-20 at 20:10 +0800, Bo-Chen Chen wrote:
> From: Guillaume Ranquet <granquet@...libre.com>
> 
> Enabling the dpi too early causes glitches on screen.
> 
> Move the call to mtk_dpi_enable() at the end of the bridge_enable
> callback to ensure everything is setup properly before enabling dpi.
> 
> Fixes: f89c696e7f63 ("drm/mediatek: mtk_dpi: Convert to bridge
> driver")

I think this problem happen in the first patch [1].

[1] 
https://git.kernel.org/pub/scm/linux/kernel/git/chunkuang.hu/linux.git/commit/drivers/gpu/drm/mediatek/mtk_dpi.c?h=mediatek-drm-next&id=9e629c17aa8d7a75b8c1d99ed42892cd8ba7cdc4

Regards,
CK

> Signed-off-by: Guillaume Ranquet <granquet@...libre.com>
> Signed-off-by: Bo-Chen Chen <rex-bc.chen@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_dpi.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_dpi.c
> b/drivers/gpu/drm/mediatek/mtk_dpi.c
> index fc76ccad0a82..220e9b18e2cd 100644
> --- a/drivers/gpu/drm/mediatek/mtk_dpi.c
> +++ b/drivers/gpu/drm/mediatek/mtk_dpi.c
> @@ -486,7 +486,6 @@ static int mtk_dpi_power_on(struct mtk_dpi *dpi)
>  	if (dpi->pinctrl && dpi->pins_dpi)
>  		pinctrl_select_state(dpi->pinctrl, dpi->pins_dpi);
>  
> -	mtk_dpi_enable(dpi);
>  	return 0;
>  
>  err_pixel:
> @@ -731,6 +730,7 @@ static void mtk_dpi_bridge_enable(struct
> drm_bridge *bridge)
>  
>  	mtk_dpi_power_on(dpi);
>  	mtk_dpi_set_display_mode(dpi, &dpi->mode);
> +	mtk_dpi_enable(dpi);
>  }
>  
>  static enum drm_mode_status