[PATCH] drm/vc4: Add support for plane alpha

[Stefan Schake]

The HVS supports mixing fixed alpha with per-pixel alpha or
setting a fixed plane alpha in case there is no per-pixel information.
This allows us to support the generic DRM plane alpha property.

Signed-off-by: Stefan Schake <***@gmail.com>
---
drivers/gpu/drm/vc4/vc4_plane.c | 14 +++++++++++++-
drivers/gpu/drm/vc4/vc4_regs.h | 1 +
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index c3a37a99e601..b06e0ec013c5 100644
--- a/drivers/gpu/drm/vc4/vc4_plane.c
+++ b/drivers/gpu/drm/vc4/vc4_plane.c
@@ -201,6 +201,7 @@ static void vc4_plane_reset(struct drm_plane *plane)
return;

plane->state = &vc4_state->base;
+ plane->state->alpha = DRM_BLEND_ALPHA_OPAQUE;
vc4_state->base.plane = plane;
}

@@ -467,6 +468,7 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
u32 ctl0_offset = vc4_state->dlist_count;
const struct hvs_format *format = vc4_get_hvs_format(fb->format->format);
int num_planes = drm_format_num_planes(format->drm);
+ bool mix_plane_alpha;
bool covers_screen;
u32 scl0, scl1, pitch0;
u32 lbm_size, tiling;
@@ -552,7 +554,7 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
/* Position Word 0: Image Positions and Alpha Value */
vc4_state->pos0_offset = vc4_state->dlist_count;
vc4_dlist_write(vc4_state,
- VC4_SET_FIELD(0xff, SCALER_POS0_FIXED_ALPHA) |
+ VC4_SET_FIELD(state->alpha >> 8, SCALER_POS0_FIXED_ALPHA) |
VC4_SET_FIELD(vc4_state->crtc_x, SCALER_POS0_START_X) |
VC4_SET_FIELD(vc4_state->crtc_y, SCALER_POS0_START_Y));

@@ -565,6 +567,13 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
SCALER_POS1_SCL_HEIGHT));
}

+ /* Don't waste cycles mixing with plane alpha if the set alpha
+ * is opaque or there is no per-pixel alpha information.
+ * In any case we use the alpha property value as the fixed alpha.
+ */
+ mix_plane_alpha = state->alpha != DRM_BLEND_ALPHA_OPAQUE &&
+ fb->format->has_alpha;
+
/* Position Word 2: Source Image Size, Alpha */
vc4_state->pos2_offset = vc4_state->dlist_count;
vc4_dlist_write(vc4_state,
@@ -572,6 +581,7 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
SCALER_POS2_ALPHA_MODE_PIPELINE :
SCALER_POS2_ALPHA_MODE_FIXED,
SCALER_POS2_ALPHA_MODE) |
+ (mix_plane_alpha ? SCALER_POS2_ALPHA_MIX : 0) |
(fb->format->has_alpha ? SCALER_POS2_ALPHA_PREMULT : 0) |
VC4_SET_FIELD(vc4_state->src_w[0], SCALER_POS2_WIDTH) |
VC4_SET_FIELD(vc4_state->src_h[0], SCALER_POS2_HEIGHT));
@@ -916,5 +926,7 @@ struct drm_plane *vc4_plane_init(struct drm_device *dev,

drm_plane_helper_add(plane, &vc4_plane_helper_funcs);

+ drm_plane_create_alpha_property(plane);
+
return plane;
}
diff --git a/drivers/gpu/drm/vc4/vc4_regs.h b/drivers/gpu/drm/vc4/vc4_regs.h
index 4af3e29d076a..d1fb6fec46eb 100644
--- a/drivers/gpu/drm/vc4/vc4_regs.h
+++ b/drivers/gpu/drm/vc4/vc4_regs.h
@@ -945,6 +945,7 @@ enum hvs_pixel_format {
#define SCALER_POS2_ALPHA_MODE_FIXED_NONZERO 2
#define SCALER_POS2_ALPHA_MODE_FIXED_OVER_0x07 3
#define SCALER_POS2_ALPHA_PREMULT BIT(29)
+#define SCALER_POS2_ALPHA_MIX BIT(28)

#define SCALER_POS2_HEIGHT_MASK VC4_MASK(27, 16)
#define SCALER_POS2_HEIGHT_SHIFT 16

[Eric Anholt]

Post by Stefan Schake
The HVS supports mixing fixed alpha with per-pixel alpha or
setting a fixed plane alpha in case there is no per-pixel information.
This allows us to support the generic DRM plane alpha property.

Don't we need to set needs_bg_fill based on alpha != OPAQUE, as well?

Other than that, looks good to me.

[Stefan Schake]

Post by Eric Anholt

Post by Stefan Schake
The HVS supports mixing fixed alpha with per-pixel alpha or
setting a fixed plane alpha in case there is no per-pixel information.
This allows us to support the generic DRM plane alpha property.

Don't we need to set needs_bg_fill based on alpha != OPAQUE, as well?
Other than that, looks good to me.

I did forget about the whole background situation, and a quick test
shows you are right: anything less than opaque has the funky
repeating pattern artifact.

Thanks, I'll send a new version.

[kbuild test robot]

Hi Stefan,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on v4.17-rc1]
[also build test ERROR on next-20180420]
[cannot apply to anholt/for-next]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url: https://github.com/0day-ci/linux/commits/Stefan-Schake/drm-vc4-Add-support-for-plane-alpha/20180423-002110
config: sh-allmodconfig (attached as .config)
compiler: sh4-linux-gnu-gcc (Debian 7.2.0-11) 7.2.0
reproduce:
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
make.cross ARCH=sh

drivers/gpu/drm/vc4/vc4_plane.c:204:14: error: 'struct drm_plane_state' has no member named 'alpha'

plane->state->alpha = DRM_BLEND_ALPHA_OPAQUE;
^~

drivers/gpu/drm/vc4/vc4_plane.c:204:24: error: 'DRM_BLEND_ALPHA_OPAQUE' undeclared (first use in this function)

plane->state->alpha = DRM_BLEND_ALPHA_OPAQUE;
^~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/vc4/vc4_plane.c:204:24: note: each undeclared identifier is reported only once for each function it appears in
In file included from drivers/gpu/drm/vc4/vc4_plane.c:28:0:
drivers/gpu/drm/vc4/vc4_plane.c: In function 'vc4_plane_mode_set':
drivers/gpu/drm/vc4/vc4_plane.c:557:23: error: 'struct drm_plane_state' has no member named 'alpha'
VC4_SET_FIELD(state->alpha >> 8, SCALER_POS0_FIXED_ALPHA) |
^
drivers/gpu/drm/vc4/vc4_regs.h:18:24: note: in definition of macro 'VC4_SET_FIELD'
uint32_t fieldval = (value) << field##_SHIFT; \
^~~~~
drivers/gpu/drm/vc4/vc4_plane.c:574:25: error: 'struct drm_plane_state' has no member named 'alpha'
mix_plane_alpha = state->alpha != DRM_BLEND_ALPHA_OPAQUE &&
^~
drivers/gpu/drm/vc4/vc4_plane.c:574:36: error: 'DRM_BLEND_ALPHA_OPAQUE' undeclared (first use in this function)
mix_plane_alpha = state->alpha != DRM_BLEND_ALPHA_OPAQUE &&
^~~~~~~~~~~~~~~~~~~~~~

drivers/gpu/drm/vc4/vc4_plane.c:952:2: error: implicit declaration of function 'drm_plane_create_alpha_property'; did you mean 'drm_plane_create_zpos_property'? [-Werror=implicit-function-declaration]

drm_plane_create_alpha_property(plane);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drm_plane_create_zpos_property
cc1: some warnings being treated as errors

vim +204 drivers/gpu/drm/vc4/vc4_plane.c

191
192 /* Called during init to allocate the plane's atomic state. */
193 static void vc4_plane_reset(struct drm_plane *plane)
194 {
195 struct vc4_plane_state *vc4_state;
196
197 WARN_ON(plane->state);
198
199 vc4_state = kzalloc(sizeof(*vc4_state), GFP_KERNEL);
200 if (!vc4_state)
201 return;
202
203 plane->state = &vc4_state->base;

204 plane->state->alpha = DRM_BLEND_ALPHA_OPAQUE;

205 vc4_state->base.plane = plane;
206 }
207

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