linux-kernel - [PATCH v4 2/2] drm/amd: use fixed dsc bits-per-pixel from edid

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Message-ID: <20251016001038.13611-6-iam@lach.pw>
Date: Thu, 16 Oct 2025 02:10:41 +0200
From: Yaroslav Bolyukin <iam@...h.pw>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Simona Vetter <simona@...ll.ch>
Cc: Harry Wentland <harry.wentland@....com>,
	Leo Li <sunpeng.li@....com>,
	Rodrigo Siqueira <siqueira@...lia.com>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	Wayne Lin <Wayne.Lin@....com>,
	amd-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	Yaroslav Bolyukin <iam@...h.pw>
Subject: [PATCH v4 2/2] drm/amd: use fixed dsc bits-per-pixel from edid

VESA vendor header from DisplayID spec may contain fixed bit per pixel
rate, it should be respected by drm driver

Signed-off-by: Yaroslav Bolyukin <iam@...h.pw>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 0d03e324d5b9..ebe5bb4eecf8 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6521,6 +6521,11 @@ static void fill_stream_properties_from_drm_display_mode(
 
 	stream->output_color_space = get_output_color_space(timing_out, connector_state);
 	stream->content_type = get_output_content_type(connector_state);
+
+	/* DisplayID Type VII pass-through timings. */
+	if (mode_in->dsc_passthrough_timings_support && info->dp_dsc_bpp != 0) {
+		stream->timing.dsc_fixed_bits_per_pixel_x16 = info->dp_dsc_bpp;
+	}
 }
 
 static void fill_audio_info(struct audio_info *audio_info,
@@ -7067,6 +7072,13 @@ create_stream_for_sink(struct drm_connector *connector,
 					&mode, preferred_mode, scale);
 
 			preferred_refresh = drm_mode_vrefresh(preferred_mode);
+
+			/*
+			 * HACK: In case of multiple supported modes, we should look at the matching mode to decide this flag.
+			 * But what is matching mode, how should it be decided?
+			 * Assuming that only preferred mode would have this flag.
+			 */
+			mode.dsc_passthrough_timings_support = preferred_mode->dsc_passthrough_timings_support;
 		}
 	}
 
@@ -7756,7 +7768,7 @@ create_validate_stream_for_sink(struct drm_connector *connector,
 			drm_dbg_kms(connector->dev, "%s:%d Validation failed with %d, retrying w/ YUV420\n",
 				    __func__, __LINE__, dc_result);
 			aconnector->force_yuv420_output = true;
-		}
+}
 		stream = create_validate_stream_for_sink(connector, drm_mode,
 							 dm_state, old_stream);
 		aconnector->force_yuv422_output = false;
-- 
2.51.0