linux-kernel - Re: [PATCH v10 1/5] drm/mediatek: ovl: Fix XRGB format breakage for blend

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Message-ID: <f86b4ebdc80e2058a530cab6989d8f1a7c7a2094.camel@mediatek.com>
Date: Wed, 9 Oct 2024 03:22:57 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: Jason-JH Lin (林睿祥) <Jason-JH.Lin@...iatek.com>,
	"me@...mthiede.com" <me@...mthiede.com>, "chunkuang.hu@...nel.org"
	<chunkuang.hu@...nel.org>, "yassine.oudjana@...il.com"
	<yassine.oudjana@...il.com>, AngeloGioacchino Del Regno
	<angelogioacchino.delregno@...labora.com>
CC: "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"alpernebiyasak@...il.com" <alpernebiyasak@...il.com>,
	Singo Chang (張興國) <Singo.Chang@...iatek.com>,
	Shawn Sung (宋孝謙) <Shawn.Sung@...iatek.com>,
	Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
	"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
	Project_Global_Chrome_Upstream_Group
	<Project_Global_Chrome_Upstream_Group@...iatek.com>,
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v10 1/5] drm/mediatek: ovl: Fix XRGB format breakage for
 blend_modes unsupported SoCs

Hi, Jason:

On Tue, 2024-10-08 at 14:47 +0800, Jason-JH.Lin wrote:
> OVL_CON_AEN is for alpha blending enable.
> For the SoC that is supported the blend_modes, OVL_CON_AEN will always
> enabled to use constant alpha and then use the ignore_pixel_alpha bit
> to do the alpha blending for XRGB8888 format.
> Note that ignore pixel alpha bit is not supported if the SoC is not
> supported the blend_modes.
> So it will break the original setting of XRGB8888 foramt for the
> blend_modes unsupported SoCs, such as MT8173.
> 
> To fix the downgrade issue, enable alpha blending only when a valid
> blend_mode or has_alpha is set.

After fixing the typo mentioned by Markus,

Reviewed-by: CK Hu <ck.hu@...iatek.com>

> 
> Fixes: bc46eb5d5d77 ("drm/mediatek: Support DRM plane alpha in OVL")
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index 89b439dcf3a6..047cd1796a51 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> @@ -473,8 +473,14 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  
>  	con = ovl_fmt_convert(ovl, fmt, blend_mode);
>  	if (state->base.fb) {
> -		con |= OVL_CON_AEN;
>  		con |= state->base.alpha & OVL_CON_ALPHA;
> +
> +		/*
> +		 * For blend_modes supported SoCs, always enable alpha blending.
> +		 * For blend_modes unsupported SoCs, enable alpha blending when has_alpha is set.
> +		 */
> +		if (blend_mode || state->base.fb->format->has_alpha)
> +			con |= OVL_CON_AEN;
>  	}
>  
>  	/* CONST_BLD must be enabled for XRGB formats although the alpha channel