drm/vc4: Add support for plane alpha

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 <stschake@gmail.com>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180421000954.18936-1-stschake@gmail.com

diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c
index c3a37a9..3483c05 100644 (file)
--- 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));
@@ -653,10 +663,11 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
                        vc4_state->crtc_w == state->crtc->mode.hdisplay &&
                        vc4_state->crtc_h == state->crtc->mode.vdisplay;
        /* Background fill might be necessary when the plane has per-pixel
-        * alpha content and blends from the background or does not cover
-        * the entire screen.
+        * alpha content or a non-opaque plane alpha and could blend from the
+        * background or does not cover the entire screen.
         */
-       vc4_state->needs_bg_fill = fb->format->has_alpha || !covers_screen;
+       vc4_state->needs_bg_fill = fb->format->has_alpha || !covers_screen ||
+                                  state->alpha != DRM_BLEND_ALPHA_OPAQUE;
 
        return 0;
 }
@@ -916,5 +927,7 @@ 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 4af3e29..d1fb6fe 100644 (file)
--- 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