On Mon, Mar 5, 2018 at 10:15 PM, Eric Anholt <eric@xxxxxxxxxx> wrote: > Stefan Schake <stschake@xxxxxxxxx> writes: > >> 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@xxxxxxxxx> >> --- >> Test program is available at https://github.com/stschake/vc4-alpha-test > > How about this as a suggestion for a patch series: > > vc4_plane_mode_set() sets ALPHA_PREMULT (POS2 bit 29) if alpha is > enabled. > > vc4_plane_mode_set() sets a new vc4_plane->needs_bg_fill boolean to > (format->has_alpha || !covers_screen) where covers_screenis the > can_position logic from drm_atomic_helper.c > > vc4_crtc_atomic_flush() updates DISPBKGND to enable background fill > (before vc4_crtc_update_dlist()) if the first plane has needs_bg_fill > set. > > vc4_plane_mode_set() strips off the alpha blend bits if > !vc4_plane->needs_bg_fill. > > This lets us keep avoiding the background fill cost in the normal case, > and fixes the case where the "primary" plane doesn't cover the screen. > It doesn't get the background fill turned back off if you transition > away from primary not covering the screen, but that seems unlikely and > harder to handle (since you would need to wait for the flip to be done > before disabling). I've sent out the series: https://patchwork.freedesktop.org/series/39411/ I don't think we need the final change since !needs_bg_fill <=> !(has_alpha||!covers_screen) <=> covers_screen && !has_alpha so we shouldn't be setting the alpha blend bits in the first place. Thanks, Stefan _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
