linux-kernel - Re: [PATCH v9 2/5] drm/mediatek: ovl: Refine ignore_pixel

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Message-ID: <0540f783d0c011b8f8ba3fa1f173616ff2e26d91.camel@mediatek.com>
Date: Tue, 8 Oct 2024 03:56:22 +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 2/5] drm/mediatek: ovl: Refine ignore_pixel_alpha
 comment and placement

Hi, Jason:

On Mon, 2024-10-07 at 15:00 +0800, Jason-JH.Lin wrote:
> Refine the comment for ignore_pixel_alpha flag and move it to
> if (state->fb) statement to make it less conditional.

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

> 
> Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index 8453a72f9e59..ddc826c42653 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> @@ -481,16 +481,16 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  		 */
>  		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
> -	 * can be ignored, or OVL will still read the value from memory.
> -	 * For RGB888 related formats, whether CONST_BLD is enabled or not won't
> -	 * affect the result. Therefore we use !has_alpha as the condition.
> -	 */
> -	if ((state->base.fb && !state->base.fb->format->has_alpha) ||
> -	    blend_mode == DRM_MODE_BLEND_PIXEL_NONE)
> -		ignore_pixel_alpha = OVL_CONST_BLEND;
> +		/*
> +		 * Although the alpha channel can be ignored, CONST_BLD must be enabled
> +		 * for XRGB format, otherwise OVL will still read the value from memory.
> +		 * For RGB888 related formats, whether CONST_BLD is enabled or not won't
> +		 * affect the result. Therefore we use !has_alpha as the condition.
> +		 */
> +		if (blend_mode == DRM_MODE_BLEND_PIXEL_NONE || !state->base.fb->format->has_alpha)
> +			ignore_pixel_alpha = OVL_CONST_BLEND;
> +	}
>  
>  	if (pending->rotation & DRM_MODE_REFLECT_Y) {
>  		con |= OVL_CON_VIRT_FLIP;