<snip> > > On 2022-05-19 16:42, Harry Wentland wrote: >> >> >> On 2022-05-13 16:22, Sung Joon Kim wrote: >>> Issue fixed: Overlay plane alpha channel blending is incorrect >>> >>> Issue tracker: https://gitlab.freedesktop.org/drm/amd/-/issues/1769 >>> >>> According to the KMS man page, there is a "Coverage" alpha blend mode >>> that assumes the pixel color values have NOT been pre-multiplied and >>> will be done when the actual blending to the background color values >>> happens. >>> >>> Previously, this mode hasn't been enabled in our driver and it was >>> assumed that all normal overlay planes are pre-multiplied by default. >>> >>> When a 3rd party app is used to input a image in a specific format, >>> e.g. PNG, as a source of a overlay plane to blend with the background >>> primary plane, the pixel color values are not pre-multiplied. So by >>> adding "Coverage" blend mode, our driver will support those cases. >>> >>> Reference: >>> https://dri.freedesktop.org/docs/drm/gpu/drm-kms.html#plane-compositi >>> on-properties >>> >>> Adding Coverage support also enables IGT kms_plane_alpha_blend >>> Coverage subtests: >>> 1. coverage-7efc >>> 2. coverage-vs-premult-vs-constant >>> >>> Signed-off-by: Sung Joon Kim <Sungjoon.Kim@xxxxxxx> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx> <snip> >>> @@ -2564,14 +2573,6 @@ void dcn10_update_mpcc(struct dc *dc, struct pipe_ctx *pipe_ctx) >>> else >>> blnd_cfg.global_alpha = 0xff; >>> >>> - /* DCN1.0 has output CM before MPC which seems to screw with >>> - * pre-multiplied alpha. >>> - */ >>> - blnd_cfg.pre_multiplied_alpha = is_rgb_cspace( >>> - pipe_ctx->stream->output_color_space) >>> - && per_pixel_alpha; >>> - >> >> Could this break color management use-cases on DCN1.x for Windows? >> Dmytro Laktyushkin added this code 5 years ago. Maybe check with him. >> >> Overall I like this patch but let's see if we can confirm that this >> won't break DCN1.x on Windows. >> >> See commit ad32734699da4dd185405637459bf915a4f4cff6. >> >> Harry > > I spoke with Dmytro and he is okay with the change > Thanks for checking. Harry > Joon >> >>> - >>> /* >>> * TODO: remove hack >>> * Note: currently there is a bug in init_hw such that diff --git >>> a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c >>> b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c >>> index e1f87bd72e4a..c117830b8b9d 100644 >>> --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c >>> +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c >>> @@ -2346,12 +2346,16 @@ void dcn20_update_mpcc(struct dc *dc, struct pipe_ctx *pipe_ctx) >>> blnd_cfg.overlap_only = false; >>> blnd_cfg.global_gain = 0xff; >>> >>> - if (per_pixel_alpha && pipe_ctx->plane_state->global_alpha) { >>> - blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA_COMBINED_GLOBAL_GAIN; >>> - blnd_cfg.global_gain = pipe_ctx->plane_state->global_alpha_value; >>> - } else if (per_pixel_alpha) { >>> - blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA; >>> + if (per_pixel_alpha) { >>> + blnd_cfg.pre_multiplied_alpha = pipe_ctx->plane_state->pre_multiplied_alpha; >>> + if (pipe_ctx->plane_state->global_alpha) { >>> + blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA_COMBINED_GLOBAL_GAIN; >>> + blnd_cfg.global_gain = pipe_ctx->plane_state->global_alpha_value; >>> + } else { >>> + blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA; >>> + } >>> } else { >>> + blnd_cfg.pre_multiplied_alpha = false; >>> blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA; >>> } >>> >>> @@ -2365,7 +2369,7 @@ void dcn20_update_mpcc(struct dc *dc, struct pipe_ctx *pipe_ctx) >>> blnd_cfg.top_gain = 0x1f000; >>> blnd_cfg.bottom_inside_gain = 0x1f000; >>> blnd_cfg.bottom_outside_gain = 0x1f000; >>> - blnd_cfg.pre_multiplied_alpha = per_pixel_alpha; >>> + >>> if (pipe_ctx->plane_state->format >>> == SURFACE_PIXEL_FORMAT_GRPH_RGBE_ALPHA) >>> blnd_cfg.pre_multiplied_alpha = false; >> >
