Re: [PATCH v9 16/21] drm/mediatek: Support "Pre-multiplied" blending in OVL

["CK Hu (胡俊光)" <ck.hu@mediatek.com>]

On Fri, 2024-06-14 at 10:46 +0800, Shawn Sung wrote:
> From: Hsiao Chien Sung <shawn.sung@mediatek.com>
> 
> Support "Pre-multiplied" alpha blending mode on in OVL.
> Before this patch, only the "coverage" mode is supported.
> 
> Signed-off-by: Hsiao Chien Sung <shawn.sung@mediatek.com>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 42 ++++++++++++++++++++-----
>  1 file changed, 34 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index 6567806cf4e2..47d0b039a616 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> @@ -52,8 +52,12 @@
>  #define GMC_THRESHOLD_HIGH	((1 << GMC_THRESHOLD_BITS) / 4)
>  #define GMC_THRESHOLD_LOW	((1 << GMC_THRESHOLD_BITS) / 8)
>  
> +#define OVL_CON_CLRFMT_MAN	BIT(23)
>  #define OVL_CON_BYTE_SWAP	BIT(24)
> -#define OVL_CON_MTX_YUV_TO_RGB	(6 << 16)
> +
> +/* OVL_CON_RGB_SWAP works only if OVL_CON_CLRFMT_MAN is enabled */
> +#define OVL_CON_RGB_SWAP	BIT(25)
> +
>  #define OVL_CON_CLRFMT_RGB	(1 << 12)
>  #define OVL_CON_CLRFMT_ARGB8888	(2 << 12)
>  #define OVL_CON_CLRFMT_RGBA8888	(3 << 12)
> @@ -61,6 +65,11 @@
>  #define OVL_CON_CLRFMT_BGRA8888	(OVL_CON_CLRFMT_ARGB8888 | OVL_CON_BYTE_SWAP)
>  #define OVL_CON_CLRFMT_UYVY	(4 << 12)
>  #define OVL_CON_CLRFMT_YUYV	(5 << 12)
> +#define OVL_CON_MTX_YUV_TO_RGB	(6 << 16)
> +#define OVL_CON_CLRFMT_PARGB8888 ((3 << 12) | OVL_CON_CLRFMT_MAN)

#define OVL_CON_CLRFMT_PARGB8888 (OVL_CON_CLRFMT_RGBA8888 | OVL_CON_CLRFMT_MAN)

But I'm confused with the naming.


> +#define OVL_CON_CLRFMT_PABGR8888 (OVL_CON_CLRFMT_PARGB8888 | OVL_CON_RGB_SWAP)

#define OVL_CON_CLRFMT_PABGR8888 (OVL_CON_CLRFMT_ABGR8888 | OVL_CON_CLRFMT_MAN)

> +#define OVL_CON_CLRFMT_PBGRA8888 (OVL_CON_CLRFMT_PARGB8888 | OVL_CON_BYTE_SWAP)

#define OVL_CON_CLRFMT_PBGRA8888 (OVL_CON_CLRFMT_BGRA8888 | OVL_CON_CLRFMT_MAN)

> +#define OVL_CON_CLRFMT_PRGBA8888 (OVL_CON_CLRFMT_PABGR8888 | OVL_CON_BYTE_SWAP)
>  #define OVL_CON_CLRFMT_RGB565(ovl)	((ovl)->data->fmt_rgb565_is_0 ? \
>  					0 : OVL_CON_CLRFMT_RGB)
>  #define OVL_CON_CLRFMT_RGB888(ovl)	((ovl)->data->fmt_rgb565_is_0 ? \
> @@ -74,6 +83,8 @@
>  #define	OVL_CON_VIRT_FLIP	BIT(9)
>  #define	OVL_CON_HORZ_FLIP	BIT(10)
>  
> +#define OVL_COLOR_ALPHA		GENMASK(31, 24)
> +
>  static inline bool is_10bit_rgb(u32 fmt)
>  {
>  	switch (fmt) {
> @@ -298,7 +309,13 @@ void mtk_ovl_config(struct device *dev, unsigned int w,
>  	if (w != 0 && h != 0)
>  		mtk_ddp_write_relaxed(cmdq_pkt, h << 16 | w, &ovl->cmdq_reg, ovl->regs,
>  				      DISP_REG_OVL_ROI_SIZE);
> -	mtk_ddp_write_relaxed(cmdq_pkt, 0x0, &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_ROI_BGCLR);
> +
> +	/*
> +	 * The background color must be opaque black (ARGB),
> +	 * otherwise the alpha blending will have no effect
> +	 */
> +	mtk_ddp_write_relaxed(cmdq_pkt, OVL_COLOR_ALPHA, &ovl->cmdq_reg,
> +			      ovl->regs, DISP_REG_OVL_ROI_BGCLR);

The coverage mode formula is:
dst.RGB = src.RGB * src.A + dst.RGB * (1 - src.A)

The pre-multiplied mode formula is:
dst.RGB = src.RGB + dst.RGB * (1 - src.A)

Both formula has no destination alpha (I think background color is last destination),
why coverage mode work fine but pre-multiplied mode has something wrong?

Regards,
CK

>  
>  	mtk_ddp_write(cmdq_pkt, 0x1, &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_RST);
>  	mtk_ddp_write(cmdq_pkt, 0x0, &ovl->cmdq_reg, ovl->regs, DISP_REG_OVL_RST);
> @@ -374,7 +391,8 @@ void mtk_ovl_layer_off(struct device *dev, unsigned int idx,
>  		      DISP_REG_OVL_RDMA_CTRL(idx));
>  }
>  
> -static unsigned int ovl_fmt_convert(struct mtk_disp_ovl *ovl, unsigned int fmt)
> +static unsigned int ovl_fmt_convert(struct mtk_disp_ovl *ovl, unsigned int fmt,
> +				    unsigned int blend_mode)
>  {
>  	/* The return value in switch "MEM_MODE_INPUT_FORMAT_XXX"
>  	 * is defined in mediatek HW data sheet.
> @@ -395,22 +413,30 @@ static unsigned int ovl_fmt_convert(struct mtk_disp_ovl *ovl, unsigned int fmt)
>  	case DRM_FORMAT_RGBA8888:
>  	case DRM_FORMAT_RGBX1010102:
>  	case DRM_FORMAT_RGBA1010102:
> -		return OVL_CON_CLRFMT_RGBA8888;
> +		return blend_mode == DRM_MODE_BLEND_COVERAGE ?
> +		       OVL_CON_CLRFMT_RGBA8888 :
> +		       OVL_CON_CLRFMT_PRGBA8888;
>  	case DRM_FORMAT_BGRX8888:
>  	case DRM_FORMAT_BGRA8888:
>  	case DRM_FORMAT_BGRX1010102:
>  	case DRM_FORMAT_BGRA1010102:
> -		return OVL_CON_CLRFMT_BGRA8888;
> +		return blend_mode == DRM_MODE_BLEND_COVERAGE ?
> +		       OVL_CON_CLRFMT_BGRA8888 :
> +		       OVL_CON_CLRFMT_PBGRA8888;
>  	case DRM_FORMAT_XRGB8888:
>  	case DRM_FORMAT_ARGB8888:
>  	case DRM_FORMAT_XRGB2101010:
>  	case DRM_FORMAT_ARGB2101010:
> -		return OVL_CON_CLRFMT_ARGB8888;
> +		return blend_mode == DRM_MODE_BLEND_COVERAGE ?
> +		       OVL_CON_CLRFMT_ARGB8888 :
> +		       OVL_CON_CLRFMT_PARGB8888;
>  	case DRM_FORMAT_XBGR8888:
>  	case DRM_FORMAT_ABGR8888:
>  	case DRM_FORMAT_XBGR2101010:
>  	case DRM_FORMAT_ABGR2101010:
> -		return OVL_CON_CLRFMT_ABGR8888;
> +		return blend_mode == DRM_MODE_BLEND_COVERAGE ?
> +		       OVL_CON_CLRFMT_ABGR8888 :
> +		       OVL_CON_CLRFMT_PABGR8888;
>  	case DRM_FORMAT_UYVY:
>  		return OVL_CON_CLRFMT_UYVY | OVL_CON_MTX_YUV_TO_RGB;
>  	case DRM_FORMAT_YUYV:
> @@ -450,7 +476,7 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
>  		return;
>  	}
>  
> -	con = ovl_fmt_convert(ovl, fmt);
> +	con = ovl_fmt_convert(ovl, fmt, blend_mode);
>  	if (state->base.fb) {
>  		con |= OVL_CON_AEN;
>  		con |= state->base.alpha & OVL_CON_ALPHA;