From 6be8ced880dfe29ce38c2d5e74489822da5c250e Mon Sep 17 00:00:00 2001 From: =?utf8?q?Timur=20Krist=C3=B3f?= Date: Tue, 21 Apr 2026 01:55:04 +0200 Subject: [PATCH] drm/amd/display: Disable 10-bit truncation and dithering on DCE 6.x MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit DCE 6.x doesn't support 10-bit truncation and 10-bit dithering because the following fields are 1-bit only: FMT_TEMPORAL_DITHER_DEPTH FMT_SPATIAL_DITHER_DEPTH FMT_TRUNCATE_DEPTH Programming these fields to "2" will program them as if the dithering option was 6-bit, resulting in sub-par picture quality and an ugly "color banding" effect. Note that a recent commit changed the default 10-bit dithering option to DITHER_OPTION_SPATIAL10 which improves the picture quality because it happens to look better, but is still not actually supported by DCE 6.x versions. When the color depth is 10-bit or more, just disable any kind of dithering options on DCE 6.x. Closes: https://gitlab.freedesktop.org/drm/amd/-/work_items/5151 Fixes: 529cad0f945c ("drm/amd/display: Add function to set dither option") Signed-off-by: Timur Kristóf Signed-off-by: Alex Deucher --- drivers/gpu/drm/amd/display/dc/core/dc_resource.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c index 19526a278b2a5..1ab76c2d0f723 100644 --- a/drivers/gpu/drm/amd/display/dc/core/dc_resource.c +++ b/drivers/gpu/drm/amd/display/dc/core/dc_resource.c @@ -5069,6 +5069,12 @@ void resource_build_bit_depth_reduction_params(struct dc_stream_state *stream, } } + if (stream->ctx->dce_version < DCE_VERSION_8_0 && + stream->timing.display_color_depth >= COLOR_DEPTH_101010) { + /* DCE 6.x doesn't support 10-bit truncation or dither options. */ + option = DITHER_OPTION_DISABLE; + } + if (option == DITHER_OPTION_DISABLE) return; -- 2.47.3