linux-kernel - Re: [PATCH v9 1/5] drm/mediatek: ovl: Fix XRGB format breakage for blend

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Message-ID: <3b1c62caf4a80892071607ce944c151541a7c7d6.camel@mediatek.com>
Date: Tue, 8 Oct 2024 03:51:45 +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 v9 1/5] drm/mediatek: ovl: Fix XRGB format breakage for
 blend_modes unsupported SoCs

Hi, Jason:

On Mon, 2024-10-07 at 15:00 +0800, Jason-JH.Lin wrote:
> If the constant alpha always enable, the SoCs that is not supported the
> ignore pixel alpha bit will still use constant alpha. That will break
> the original constant alpha setting of XRGB foramt for blend_modes
> unsupported SoCs, such as MT8173.
> 
> Note that ignore pixel alpha bit is suppored if the SoC support the
> blend_modes.
> Make the constatnt alpha only enable when having a vliad blend_mode or
> setting the has_alpha to fix the downgrade issue.

It's alpha blending enable, not constant alpha enable.

> 
> 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..8453a72f9e59 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 constant alpha.
> +		 * For blend_modes unsupported SoCs, enable constant alpha when has_alpha is set.

It's alpha blending enable, not constant alpha enable.

Regards,
CK

> +		 */
> +		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