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Date: Tue, 11 Jun 2024 09:39:24 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: Shawn Sung (宋孝謙) <Shawn.Sung@...iatek.com>,
"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC: "linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Bibby Hsieh (謝濟遠) <Bibby.Hsieh@...iatek.com>,
"jason-ch.chen@...iatek.corp-partner.google.com"
<jason-ch.chen@...iatek.corp-partner.google.com>,
Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
"daniel@...ll.ch" <daniel@...ll.ch>, "p.zabel@...gutronix.de"
<p.zabel@...gutronix.de>, "dri-devel@...ts.freedesktop.org"
<dri-devel@...ts.freedesktop.org>, "airlied@...il.com" <airlied@...il.com>,
"sean@...rly.run" <sean@...rly.run>, "matthias.bgg@...il.com"
<matthias.bgg@...il.com>, "fshao@...omium.org" <fshao@...omium.org>,
"linux-arm-kernel@...ts.infradead.org"
<linux-arm-kernel@...ts.infradead.org>,
"angelogioacchino.delregno@...labora.com"
<angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v8 11/16] drm/mediatek: Support "Pre-multiplied" blending
in OVL
Hi, Shawn:
On Thu, 2024-06-06 at 17:26 +0800, Shawn Sung wrote:
> From: Hsiao Chien Sung <shawn.sung@...iatek.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@...iatek.com>
> ---
> drivers/gpu/drm/mediatek/mtk_disp_ovl.c | 40 +++++++++++++++++++++----
> 1 file changed, 34 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> index 54a6f11aa867..de1633988921 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_ovl.c
> @@ -52,13 +52,16 @@
> #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)
> +#define OVL_CON_RGB_SWAP BIT(25)
> #define OVL_CON_CLRFMT_RGB (1 << 12)
> #define OVL_CON_CLRFMT_RGBA8888 (2 << 12)
> #define OVL_CON_CLRFMT_ARGB8888 (3 << 12)
> #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 (OVL_CON_CLRFMT_ARGB8888 | OVL_CON_CLRFMT_MAN)
> #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 ? \
> @@ -72,6 +75,8 @@
> #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) {
> @@ -296,7 +301,13 @@ 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?
>
> 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);
> @@ -372,7 +383,8 @@ 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.
> @@ -391,21 +403,35 @@ static unsigned int ovl_fmt_convert(struct mtk_disp_ovl *ovl, unsigned int fmt)
> return OVL_CON_CLRFMT_RGB888(ovl) | OVL_CON_BYTE_SWAP;
> case DRM_FORMAT_RGBX8888:
> case DRM_FORMAT_RGBA8888:
> + return blend_mode == DRM_MODE_BLEND_COVERAGE ?
> + OVL_CON_CLRFMT_ARGB8888 :
> + OVL_CON_CLRFMT_PARGB8888;
> case DRM_FORMAT_RGBX1010102:
> case DRM_FORMAT_RGBA1010102:
> return OVL_CON_CLRFMT_ARGB8888;
> case DRM_FORMAT_BGRX8888:
> case DRM_FORMAT_BGRA8888:
> + return OVL_CON_BYTE_SWAP |
> + (blend_mode == DRM_MODE_BLEND_COVERAGE ?
> + OVL_CON_CLRFMT_ARGB8888 :
> + OVL_CON_CLRFMT_PARGB8888);
> case DRM_FORMAT_BGRX1010102:
> case DRM_FORMAT_BGRA1010102:
> return OVL_CON_CLRFMT_ARGB8888 | OVL_CON_BYTE_SWAP;
> case DRM_FORMAT_XRGB8888:
> case DRM_FORMAT_ARGB8888:
> + return blend_mode == DRM_MODE_BLEND_COVERAGE ?
> + OVL_CON_CLRFMT_RGBA8888 :
> + OVL_CON_CLRFMT_PARGB8888;
In pre-multiplied mode, DRM_FORMAT_RGBA8888 and DRM_FORMAT_ARGB8888 would return the same value OVL_CON_CLRFMT_PARGB8888,
so how does hardware distinguish these two format?
> case DRM_FORMAT_XRGB2101010:
> case DRM_FORMAT_ARGB2101010:
> return OVL_CON_CLRFMT_RGBA8888;
> case DRM_FORMAT_XBGR8888:
> case DRM_FORMAT_ABGR8888:
> + return OVL_CON_RGB_SWAP |
> + (blend_mode == DRM_MODE_BLEND_COVERAGE ?
> + OVL_CON_CLRFMT_RGBA8888 :
> + OVL_CON_CLRFMT_PARGB8888);
Originally, DRM_MODE_BLEND_COVERAGE and DRM_FORMAT_ABGR8888 would return
OVL_CON_CLRFMT_RGBA8888 | OVL_CON_BYTE_SWAP
but this patch return
OVL_CON_CLRFMT_RGBA8888 | OVL_CON_RGB_SWAP
This is not related to pre-multiplied, so separate this to another patch.
> case DRM_FORMAT_XBGR2101010:
> case DRM_FORMAT_ABGR2101010:
> return OVL_CON_CLRFMT_RGBA8888 | OVL_CON_BYTE_SWAP;
> @@ -448,9 +474,11 @@ void mtk_ovl_layer_config(struct device *dev, unsigned int idx,
> return;
> }
>
> - con = ovl_fmt_convert(ovl, fmt);
> - if (state->base.fb && state->base.fb->format->has_alpha)
> - con |= OVL_CON_AEN | OVL_CON_ALPHA;
> + con = ovl_fmt_convert(ovl, fmt, blend_mode);
> + if (state->base.fb) {
> + con |= OVL_CON_AEN;
> + con |= state->base.alpha & OVL_CON_ALPHA;
This modification is to support constant alpha, not related to pre-multiplied alpha. So separate this to another patch.
Regards,
CK
> + }
>
> /* CONST_BLD must be enabled for XRGB formats although the alpha channel
> * can be ignored, or OVL will still read the value from memory.
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