From: Melissa Wen <mwen@xxxxxxxxxx> commit e4f1541caf60fcbe5a59e9d25805c0b5865e546a upstream. "Pre-multiplied" is the default pixel blend mode for KMS/DRM, as documented in supported_modes of drm_plane_create_blend_mode_property(): https://cgit.freedesktop.org/drm/drm-misc/tree/drivers/gpu/drm/drm_blend.c In this mode, both 'pixel alpha' and 'plane alpha' participate in the calculation, as described by the pixel blend mode formula in KMS/DRM documentation: out.rgb = plane_alpha * fg.rgb + (1 - (plane_alpha * fg.alpha)) * bg.rgb Considering the blend config mechanisms we have in the driver so far, the alpha mode that better fits this blend mode is the _PER_PIXEL_ALPHA_COMBINED_GLOBAL_GAIN, where the value for global_gain is the plane alpha (global_alpha). With this change, alpha property stops to be ignored. It also addresses Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1734 v2: * keep the 8-bit value for global_alpha_value (Nicholas) * correct the logical ordering for combined global gain (Nicholas) * apply to dcn10 too (Nicholas) Signed-off-by: Melissa Wen <mwen@xxxxxxxxxx> Tested-by: Rodrigo Siqueira <Rodrigo.Siqueira@xxxxxxx> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx> Tested-by: Simon Ser <contact@xxxxxxxxxxx> Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c | 14 +++++++++----- drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c | 14 +++++++++----- 2 files changed, 18 insertions(+), 10 deletions(-) --- a/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c +++ b/drivers/gpu/drm/amd/display/dc/dcn10/dcn10_hw_sequencer.c @@ -2202,14 +2202,18 @@ static void dcn10_update_mpcc(struct dc &blnd_cfg.black_color); } - if (per_pixel_alpha) - blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA; - else - blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA; - 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; + } else { + blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA; + } + if (pipe_ctx->plane_state->global_alpha) blnd_cfg.global_alpha = pipe_ctx->plane_state->global_alpha_value; else --- a/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/dcn20/dcn20_hwseq.c @@ -1740,14 +1740,18 @@ static void dcn20_update_mpcc(struct dc pipe_ctx, &blnd_cfg.black_color); } - if (per_pixel_alpha) - blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_PER_PIXEL_ALPHA; - else - blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA; - 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; + } else { + blnd_cfg.alpha_mode = MPCC_ALPHA_BLEND_MODE_GLOBAL_ALPHA; + } + if (pipe_ctx->plane_state->global_alpha) blnd_cfg.global_alpha = pipe_ctx->plane_state->global_alpha_value; else
