FAILED: patch "[PATCH] drm/amd/display: Preserve eDP mode on initial ASSR failure" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 5e08102d1d336593160d1434261d50b0c0f6cbe6
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026100541-wages-celibate-8917@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 5e08102d1d336593160d1434261d50b0c0f6cbe6 Mon Sep 17 00:00:00 2001
From: Arthur Heymans <[email protected]>
Date: Sat, 12 Sep 2026 17:11:37 +0200
Subject: [PATCH] drm/amd/display: Preserve eDP mode on initial ASSR failure

Commit 56d8ce9d8c17 ("drm/amd/display: Apply correct panel mode when reinitializing hardware") made ASSR failure fall back to the default panel mode unless eDP mode had previously been applied.

However, dc_link is zero-initialized and DP_PANEL_MODE_DEFAULT is zero. Before the first call to dp_set_panel_mode(), panel_mode therefore looks like a previously applied default mode. If ASSR setup fails during the first link training attempt, the driver incorrectly trains the eDP link using the default scrambling mode.

On a Google Vilboz Chromebook running self-built coreboot firmware and PSP verstage, this leaves the panel mostly black with corrupted output along the top edge.

Track whether panel_mode has actually been initialized, and only consult the saved mode after it has been applied. This retains the recovery behavior while preserving eDP mode during initial link training.

index 705c500ad711..871063f809dc 100644
@@ -1905,6 +1905,7 @@ struct dc_scratch_space {
 	struct ddc_service *ddc;
 
 	enum dp_panel_mode panel_mode;
+	bool panel_mode_initialized;
 	bool aux_mode;
 
 	/* Private to DC core */

index 16951a9550f2..21dd91fc8010 100644
@@ -93,6 +93,7 @@ void dp_set_panel_mode(struct dc_link *link, enum dp_panel_mode panel_mode)
 	}
 
 	link->panel_mode = panel_mode;
+	link->panel_mode_initialized = true;
 	DC_LOG_DETECTION_DP_CAPS("%d eDP panel mode supported: %d, enabled: %d\n",
 				 link->link_index,
 				 link->dpcd_caps.panel_mode_edp,

@@ -1297,7 +1298,8 @@ void edp_set_panel_assr(struct dc_link *link, struct pipe_ctx *pipe_ctx,
 
 		result = cp_psp->funcs.enable_assr(cp_psp->handle, link);
 
-		if (!result && link->panel_mode != DP_PANEL_MODE_EDP)
+		if (!result && link->panel_mode_initialized &&
+		    link->panel_mode != DP_PANEL_MODE_EDP)
 			*panel_mode = DP_PANEL_MODE_DEFAULT;
 	}
 }

From: Arthur Heymans <[email protected]>

[ Upstream commit 5e08102d1d336593160d1434261d50b0c0f6cbe6 ]

Commit 56d8ce9d8c17 ("drm/amd/display: Apply correct panel mode when reinitializing hardware") made ASSR failure fall back to the default panel mode unless eDP mode had previously been applied.

However, dc_link is zero-initialized and DP_PANEL_MODE_DEFAULT is zero. Before the first call to dp_set_panel_mode(), panel_mode therefore looks like a previously applied default mode. If ASSR setup fails during the first link training attempt, the driver incorrectly trains the eDP link using the default scrambling mode.

On a Google Vilboz Chromebook running self-built coreboot firmware and PSP verstage, this leaves the panel mostly black with corrupted output along the top edge.

Track whether panel_mode has actually been initialized, and only consult the saved mode after it has been applied. This retains the recovery behavior while preserving eDP mode during initial link training.

---
 drivers/gpu/drm/amd/display/dc/dc.h                           | 1 +
 .../amd/display/dc/link/protocols/link_edp_panel_control.c    | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

index a4f6ff7155c2a..f7cd6cb06638b 100644
@@ -1721,6 +1721,7 @@ struct dc_link {
 	struct ddc_service *ddc;
 
 	enum dp_panel_mode panel_mode;
+	bool panel_mode_initialized;
 	bool aux_mode;
 
 	/* Private to DC core */

index fa642f4b88c2d..17220177479a3 100644
@@ -91,6 +91,7 @@ void dp_set_panel_mode(struct dc_link *link, enum dp_panel_mode panel_mode)
 	}
 
 	link->panel_mode = panel_mode;
+	link->panel_mode_initialized = true;
 	DC_LOG_DETECTION_DP_CAPS("Link: %d eDP panel mode supported: %d "
 		 "eDP panel mode enabled: %d \n",
 		 link->link_index,

@@ -1231,7 +1232,8 @@ void edp_set_panel_assr(struct dc_link *link, struct pipe_ctx *pipe_ctx,
 
 		result = cp_psp->funcs.enable_assr(cp_psp->handle, link);
 
-		if (!result && link->panel_mode != DP_PANEL_MODE_EDP)
+		if (!result && link->panel_mode_initialized &&
+		    link->panel_mode != DP_PANEL_MODE_EDP)
 			*panel_mode = DP_PANEL_MODE_DEFAULT;
 	}
 }

2.53.0