We allow alpha formats on the primary plane but a partially transparent framebuffer will cause a corrupted display. With this change black pixels are output instead, in line with the behavior for other DRM drivers.
Signed-off-by: Stefan Schake stschake@gmail.com --- Test program is available at https://github.com/stschake/vc4-alpha-test
drivers/gpu/drm/vc4/vc4_plane.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/vc4/vc4_plane.c b/drivers/gpu/drm/vc4/vc4_plane.c index 61ad955..8c829fa 100644 --- a/drivers/gpu/drm/vc4/vc4_plane.c +++ b/drivers/gpu/drm/vc4/vc4_plane.c @@ -521,6 +521,7 @@ 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 primary_plane = state->crtc->primary == plane; u32 scl0, scl1, pitch0; u32 lbm_size, tiling; unsigned long irqflags; @@ -620,8 +621,12 @@ static int vc4_plane_mode_set(struct drm_plane *plane,
/* Position Word 2: Source Image Size, Alpha Mode */ vc4_state->pos2_offset = vc4_state->dlist_count; + /* We do not enable the HVS background color fill so the primary plane + * must be opaque to avoid display artifacts. Achieve this by always + * using fixed alpha (initialized to 0xff above) on the primary plane. + */ vc4_dlist_write(vc4_state, - VC4_SET_FIELD(fb->format->has_alpha ? + VC4_SET_FIELD(fb->format->has_alpha && !primary_plane ? SCALER_POS2_ALPHA_MODE_PIPELINE : SCALER_POS2_ALPHA_MODE_FIXED, SCALER_POS2_ALPHA_MODE) |