Re: [PATCH v3 11/17] drm/mediatek: drm/mediatek: Export OVL ignore pixel alpha function

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

On Thu, 2025-05-15 at 17:34 +0800, paul-pl.chen wrote:
> From: Nancy Lin <nancy.lin@mediatek.com>
> 
> For the new BLENDER component, the OVL ignore pixel alpha logic
> should be exported as a function and reused it.
> 
> Signed-off-by: Nancy Lin <nancy.lin@mediatek.com>
> Signed-off-by: Paul-pl Chen <paul-pl.chen@mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 24 ++++++++++++++++++++++--
>  drivers/gpu/drm/mediatek/mtk_disp_ovl.h |  1 +
>  2 files changed, 23 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index a516b7c82b5a..747898a574da 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> @@ -211,6 +211,23 @@ void mtk_ovl_disable_vblank(struct device *dev)
>  	writel_relaxed(0x0, ovl->regs + DISP_REG_OVL_INTEN);
>  }
>  
> +bool mtk_ovl_is_ignore_pixel_alpha(struct mtk_plane_state *state, unsigned int blend_mode)
> +{
> +	if (!state->base.fb)
> +		return false;
> +	/*
> +	 * 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)
> +		return true;
> +
> +	return false;
> +}
> +
>  u32 mtk_ovl_get_blend_modes(struct device *dev)
>  {
>  	struct mtk_disp_ovl *ovl = dev_get_drvdata(dev);
> @@ -539,7 +556,7 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  	unsigned int rotation = pending->rotation;
>  	unsigned int offset = (pending->y << 16) | pending->x;
>  	unsigned int src_size = (pending->height << 16) | pending->width;
> -	unsigned int blend_mode = state->base.pixel_blend_mode;
> +	unsigned int blend_mode = mtk_ovl_get_blend_mode(state, ovl->data->blend_modes);

I would like previous patch is about color format and this patch is about alpha blend.
You add mtk_ovl_get_blend_mode() in previous patch.
So remove mtk_ovl_get_blend_mode() in previous patch and add it in this patch.

In original design, blend_mode is only changed in mtk_ovl_format_convert(),
but this patch chagne blend_mode in mtk_ovl_layer_config().

In order to keep original behavior,
In below, where using blend_mode is chagned to use state->base.pixel_blend_mode,
so it's not necessary to have a variable blend_mode.

Regards,
CK

>  	unsigned int ignore_pixel_alpha = 0;
>  	unsigned int con;
>  
> @@ -557,7 +574,7 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  		 * 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)
> +		if (state->base.pixel_blend_mode || state->base.fb->format->has_alpha)
>  			con |= OVL_CON_AEN;
>  	}
>  
> @@ -584,6 +601,9 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  
>  	mtk_ddp_write_relaxed(cmdq_pkt, con, &ovl->cmdq_reg, ovl->regs,
>  			      DISP_REG_OVL_CON(idx));
> +
> +	if (mtk_ovl_is_ignore_pixel_alpha(state, blend_mode))
> +		ignore_pixel_alpha = OVL_CONST_BLEND;
>  	mtk_ddp_write_relaxed(cmdq_pkt, pitch_lsb | ignore_pixel_alpha,
>  			      &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_PITCH(idx));
>  	mtk_ddp_write_relaxed(cmdq_pkt, src_size, &ovl->cmdq_reg, ovl->regs,
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.h b/drivers/gpu/drm/mediatek/mtk_disp_ovl.h
> index 3f7d7d54479d..431567538eb5 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.h
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.h
> @@ -20,6 +20,7 @@ extern const u32 mt8195_ovl_formats[];
>  extern const size_t mt8195_ovl_formats_len;
>  
>  bool mtk_ovl_is_10bit_rgb(unsigned int fmt);
> +bool mtk_ovl_is_ignore_pixel_alpha(struct mtk_plane_state *state, unsigned int blend_mode);
>  unsigned int mtk_ovl_get_blend_mode(struct mtk_plane_state *state, unsigned int blend_modes);
>  unsigned int mtk_ovl_fmt_convert(unsigned int fmt, unsigned int blend_mode,
>  				 bool fmt_rgb565_is_0, bool color_convert,