[PATCH v4 3/4] drm/sun4i: Add support for premulti/coverage blending mode handling

From: Roman Stratiienko
Date: Mon Mar 02 2020 - 05:32:39 EST

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Argument:

All information below is author's understanding of underlying processes.
This information was obtained from DE2.0-3.0 datasheet analysis and
analysis of different DRM driver source code and commit messages.

Input buffers could have 2 ways of holding pixel alpha channel value.
1. Coverage means that in case of transparency - only alpha channel changes.
Example of 50% transparent white pixel: R=0xff B=0xff B=0xff A=0x7f

2. Premultiply means that RGB pixel values should be dimmed proportional to
alpha channel value. Alpha channel value has also to be set in this case.
Example of 50% transparent white pixel: R=0x7f B=0x7f B=0x7f A=0x7f

Userspace informs DRM/KMS which blending type frame buffer uses with
'pixel blend mode' property.

Allwinner DE2.0 and DE3.0 have 2 block of image processing:
Overlay and Blending. Both should aware of blending type are used in the buffer.

Overlay block uses this information to:
1. Unify blending types if more then 1 overlay channel are used. It can unify it
only as premultiplied by converting coverage to premultiplied.
2. Calculate correct pixel value in case of applying plane alpha.
For coverage alpha only alpha channel should be affected:
[Ro=Ri, Go=Gi, Bo=Bi, Ao=Ai*AGlobal]
For premultiplied alpha all 4 channels should be affected:
[Ro=Ri*AGlobal, Go=Gi*AGlobal, Bo=Bi*AGlobal, Ao=Ai*AGlobal]

Blending functional block should aware of blending type each pipe
channel uses. Otherwise image can't blend correctly.

In case we've specified premultiplied format for blending PIPE0, blender
converts premultiplied RGB values to original (divides by normalized Alpha).
In case for some reason pixel value after division exceeds 0xff, blender clamps
it to 0xff. [Was discovered in experimental way]
If image that passed through PIPE1-3 restored to coverage before mixing or used
in premultiplied form still require testing and out of scope of this patch.

Implementation:

1. Add blend property to UI channel
2. Add blend property to VI channel in case of DE3.0 used
3. Make all DE2.0 UI and DE3.0 VI overlay channels to use premultiply format.
Mark all blending pipes as premultiply except DE2.0 VI plane.
4. If DRM plane uses coverage blending format, set blending mode register
to convert it to premultiply.

Signed-off-by: Roman Stratiienko <r.stratiienko@xxxxxxxxx>

--

v4:
- Initial version (Depends on unmerged patches from patchset)
---
drivers/gpu/drm/sun4i/sun8i_mixer.h | 2 ++
drivers/gpu/drm/sun4i/sun8i_ui_layer.c | 33 ++++++++++++++++++-----
drivers/gpu/drm/sun4i/sun8i_ui_layer.h | 5 ++++
drivers/gpu/drm/sun4i/sun8i_vi_layer.c | 36 +++++++++++++++++++++-----
drivers/gpu/drm/sun4i/sun8i_vi_layer.h | 5 ++++
5 files changed, 69 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/sun4i/sun8i_mixer.h b/drivers/gpu/drm/sun4i/sun8i_mixer.h
index 915479cc3077..8a18372938d5 100644
--- a/drivers/gpu/drm/sun4i/sun8i_mixer.h
+++ b/drivers/gpu/drm/sun4i/sun8i_mixer.h
@@ -70,6 +70,8 @@
#define SUN8I_MIXER_BLEND_ROUTE_PIPE_MSK(n) (0xf << ((n) << 2))
#define SUN8I_MIXER_BLEND_ROUTE_PIPE_SHIFT(n) ((n) << 2)

+#define SUN8I_MIXER_BLEND_PREMULTIPLY_EN(pipe) BIT(pipe)
+
#define SUN8I_MIXER_BLEND_OUTCTL_INTERLACED BIT(1)

#define SUN50I_MIXER_BLEND_CSC_CTL_EN(ch) BIT(ch)
diff --git a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
index 5278032567a3..dd6145f80c36 100644
--- a/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_ui_layer.c
@@ -73,10 +73,12 @@ static void sun8i_ui_layer_enable(struct sun8i_mixer *mixer, int channel,
}

static void sun8i_ui_layer_update_alpha(struct sun8i_mixer *mixer, int channel,
- int overlay, struct drm_plane *plane)
+ int overlay, struct drm_plane *plane,
+ unsigned int zpos)
{
- u32 mask, val, ch_base;
+ u32 mask, val, ch_base, bld_base;

+ bld_base = sun8i_blender_base(mixer);
ch_base = sun8i_channel_base(mixer, channel);

mask = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_MASK |
@@ -84,13 +86,27 @@ static void sun8i_ui_layer_update_alpha(struct sun8i_mixer *mixer, int channel,

val = SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA(plane->state->alpha >> 8);

- val |= (plane->state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
- SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_PIXEL :
- SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_COMBINED;
+ if (plane->state->pixel_blend_mode == DRM_MODE_BLEND_PIXEL_NONE) {
+ val |= SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_LAYER;
+ } else {
+ val |= (plane->state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
+ SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_PIXEL :
+ SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_COMBINED;
+
+ if (plane->state->pixel_blend_mode == DRM_MODE_BLEND_COVERAGE)
+ val |= SUN8I_MIXER_CHAN_UI_LAYER_ATTR_BLEND_COV2PREMUL;
+ else
+ val |= SUN8I_MIXER_CHAN_UI_LAYER_ATTR_BLEND_PREMULTI;
+ }

regmap_update_bits(mixer->engine.regs,
SUN8I_MIXER_CHAN_UI_LAYER_ATTR(ch_base, overlay),
mask, val);
+
+ regmap_update_bits(mixer->engine.regs,
+ SUN8I_MIXER_BLEND_PREMULTIPLY(bld_base),
+ SUN8I_MIXER_BLEND_PREMULTIPLY_EN(zpos),
+ SUN8I_MIXER_BLEND_PREMULTIPLY_EN(zpos));
}

static int sun8i_ui_layer_update_coord(struct sun8i_mixer *mixer, int channel,
@@ -280,7 +296,7 @@ static void sun8i_ui_layer_atomic_update(struct drm_plane *plane,
sun8i_ui_layer_update_coord(mixer, layer->channel,
layer->overlay, plane, zpos);
sun8i_ui_layer_update_alpha(mixer, layer->channel,
- layer->overlay, plane);
+ layer->overlay, plane, zpos);
sun8i_ui_layer_update_formats(mixer, layer->channel,
layer->overlay, plane);
sun8i_ui_layer_update_buffer(mixer, layer->channel,
@@ -361,6 +377,11 @@ struct sun8i_ui_layer *sun8i_ui_layer_init_one(struct drm_device *drm,
return ERR_PTR(ret);
}

+ drm_plane_create_blend_mode_property(&layer->plane,
+ BIT(DRM_MODE_BLEND_PREMULTI) |
+ BIT(DRM_MODE_BLEND_COVERAGE) |
+ BIT(DRM_MODE_BLEND_PIXEL_NONE));
+
ret = drm_plane_create_zpos_property(&layer->plane, channel,
0, plane_cnt - 1);
if (ret) {
diff --git a/drivers/gpu/drm/sun4i/sun8i_ui_layer.h b/drivers/gpu/drm/sun4i/sun8i_ui_layer.h
index e3e32ee1178d..c5136f4841bc 100644
--- a/drivers/gpu/drm/sun4i/sun8i_ui_layer.h
+++ b/drivers/gpu/drm/sun4i/sun8i_ui_layer.h
@@ -41,6 +41,11 @@
#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_FBFMT_OFFSET 8
#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MASK GENMASK(31, 24)
#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA(x) ((x) << 24)
+#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_BLEND_MASK GENMASK(16, 17)
+
+#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_BLEND_COVERAGE ((0) << 16)
+#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_BLEND_COV2PREMUL ((1) << 16)
+#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_BLEND_PREMULTI ((2) << 16)

#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_PIXEL ((0) << 1)
#define SUN8I_MIXER_CHAN_UI_LAYER_ATTR_ALPHA_MODE_LAYER ((1) << 1)
diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
index f2469b5e97ee..e6d8a539614f 100644
--- a/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
+++ b/drivers/gpu/drm/sun4i/sun8i_vi_layer.c
@@ -66,11 +66,13 @@ static void sun8i_vi_layer_enable(struct sun8i_mixer *mixer, int channel,
}

static void sun8i_vi_layer_update_alpha(struct sun8i_mixer *mixer, int channel,
- int overlay, struct drm_plane *plane)
+ int overlay, struct drm_plane *plane,
+ unsigned int zpos)
{
- u32 mask, val, ch_base;
+ u32 mask, val, ch_base, bld_base;

ch_base = sun8i_channel_base(mixer, channel);
+ bld_base = sun8i_blender_base(mixer);

if (mixer->cfg->is_de3) {
mask = SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MASK |
@@ -78,9 +80,18 @@ static void sun8i_vi_layer_update_alpha(struct sun8i_mixer *mixer, int channel,
val = SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA
(plane->state->alpha >> 8);

- val |= (plane->state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
- SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_PIXEL :
- SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_COMBINED;
+ if (plane->state->pixel_blend_mode == DRM_MODE_BLEND_PIXEL_NONE) {
+ val |= SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_LAYER;
+ } else {
+ val |= (plane->state->alpha == DRM_BLEND_ALPHA_OPAQUE) ?
+ SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_PIXEL :
+ SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_COMBINED;
+
+ if (plane->state->pixel_blend_mode == DRM_MODE_BLEND_COVERAGE)
+ val |= SUN50I_MIXER_CHAN_VI_LAYER_ATTR_BLEND_COV2PREMUL;
+ else
+ val |= SUN50I_MIXER_CHAN_VI_LAYER_ATTR_BLEND_PREMULTI;
+ }

regmap_update_bits(mixer->engine.regs,
SUN8I_MIXER_CHAN_VI_LAYER_ATTR(ch_base,
@@ -93,6 +104,13 @@ static void sun8i_vi_layer_update_alpha(struct sun8i_mixer *mixer, int channel,
SUN8I_MIXER_FCC_GLOBAL_ALPHA
(plane->state->alpha >> 8));
}
+
+ regmap_update_bits(mixer->engine.regs,
+ SUN8I_MIXER_BLEND_PREMULTIPLY(bld_base),
+ SUN8I_MIXER_BLEND_PREMULTIPLY_EN(zpos),
+ (mixer->cfg->is_de3) ?
+ SUN8I_MIXER_BLEND_PREMULTIPLY_EN(zpos) : 0);
+
}

static int sun8i_vi_layer_update_coord(struct sun8i_mixer *mixer, int channel,
@@ -396,7 +414,7 @@ static void sun8i_vi_layer_atomic_update(struct drm_plane *plane,
sun8i_vi_layer_update_coord(mixer, layer->channel,
layer->overlay, plane, zpos);
sun8i_vi_layer_update_alpha(mixer, layer->channel,
- layer->overlay, plane);
+ layer->overlay, plane, zpos);
sun8i_vi_layer_update_formats(mixer, layer->channel,
layer->overlay, plane);
sun8i_vi_layer_update_buffer(mixer, layer->channel,
@@ -504,6 +522,12 @@ struct sun8i_vi_layer *sun8i_vi_layer_init_one(struct drm_device *drm,
}
}

+ if (mixer->cfg->is_de3)
+ drm_plane_create_blend_mode_property
+ (&layer->plane, BIT(DRM_MODE_BLEND_PREMULTI) |
+ BIT(DRM_MODE_BLEND_COVERAGE) |
+ BIT(DRM_MODE_BLEND_PIXEL_NONE));
+
ret = drm_plane_create_zpos_property(&layer->plane, index,
0, plane_cnt - 1);
if (ret) {
diff --git a/drivers/gpu/drm/sun4i/sun8i_vi_layer.h b/drivers/gpu/drm/sun4i/sun8i_vi_layer.h
index 48c399e1c86d..a1cf0ff16543 100644
--- a/drivers/gpu/drm/sun4i/sun8i_vi_layer.h
+++ b/drivers/gpu/drm/sun4i/sun8i_vi_layer.h
@@ -43,6 +43,11 @@
#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_MASK GENMASK(2, 1)
#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MASK GENMASK(31, 24)
#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA(x) ((x) << 24)
+#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_BLEND_MASK GENMASK(16, 17)
+
+#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_BLEND_COVERAGE ((0) << 16)
+#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_BLEND_COV2PREMUL ((1) << 16)
+#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_BLEND_PREMULTI ((2) << 16)

#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_PIXEL ((0) << 1)
#define SUN50I_MIXER_CHAN_VI_LAYER_ATTR_ALPHA_MODE_LAYER ((1) << 1)
--
2.17.1

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