drm/amd/display: Add Core 2 Workaround Manager scaffolding

[Why]
Core needs a Layer-2 post-build stage that can edit a built BLS list
for errata before the Executor runs. Inline workarounds stay scattered
until that manager exists.

[How]
Add an empty-registry Workaround Manager over block_sequence_state.
Keep the restore image in BSS so the kernel frame stays small, and
reject growth past MAX_HWSS_BLOCK_SEQUENCE_SIZE. Name the committed
state field current_state so the Linux current macro does not expand
it.

Reviewed-by: Dillon Varone <dillon.varone@amd.com>
Reviewed-by: Jun Lei <jun.lei@amd.com>
Signed-off-by: Tony Cheng <tony.cheng@amd.com>
Signed-off-by: Roman Li <roman.li@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

3 files changed, 121 insertions, 0 deletions

diff --git a/drivers/gpu/drm/amd/display/dc/Makefile b/drivers/gpu/drm/amd/display/dc/Makefile
index 58800522dfd9..7338125b117b 100644
--- a/drivers/gpu/drm/amd/display/dc/Makefile
+++ b/drivers/gpu/drm/amd/display/dc/Makefile
@@ -86,6 +86,7 @@ FILES += core2/dc_core2_init.o
 FILES += bls_builder/bls_builder.o
 FILES += bls_builder/dcn401_init_builder.o
 FILES += bls_executor/bls_executor.o
+FILES += workaround_manager/workaround_manager.o
 
 AMD_DISPLAY_FILES += $(addprefix $(AMDDALPATH)/dc/, $(FILES))
 
diff --git a/drivers/gpu/drm/amd/display/dc/workaround_manager/workaround_manager.c b/drivers/gpu/drm/amd/display/dc/workaround_manager/workaround_manager.c
new file mode 100644
index 000000000000..067a7069186b
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/dc/workaround_manager/workaround_manager.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright 2026 Advanced Micro Devices, Inc.
+ */
+
+#include "dm_services.h"
+#include "workaround_manager/workaround_manager.h"
+
+static const struct workaround_manager dc2_wam_empty = {
+	.registry = NULL,
+	.count = 0,
+};
+
+/* BSS, not the stack: 64 block_sequence entries exceed the kernel frame limit. */
+static struct block_sequence dc2_wam_saved_steps[DC2_BLS_MAX_STEPS];
+
+const struct workaround_manager *dc2_workaround_manager_get(void)
+{
+	return &dc2_wam_empty;
+}
+
+enum workaround_manager_result workaround_manager_apply(
+		const struct workaround_manager *wam,
+		struct block_sequence_state *bls,
+		const struct workaround_context *ctx)
+{
+	struct block_sequence *saved_steps = dc2_wam_saved_steps;
+	enum workaround_manager_result result;
+	unsigned int saved_num;
+	unsigned int i;
+
+	if (!wam || !bls || !bls->steps || !bls->num_steps || !ctx ||
+			*bls->num_steps > MAX_HWSS_BLOCK_SEQUENCE_SIZE ||
+			(wam->count && !wam->registry))
+		return WAM_INVALID_INPUT;
+
+	/* Snapshot buffer is DC2_BLS_MAX_STEPS; larger built lists stay unmodified. */
+	if (*bls->num_steps > DC2_BLS_MAX_STEPS) {
+		if (!wam->count)
+			return WAM_OK;
+		return WAM_INVALID_INPUT;
+	}
+
+	saved_num = *bls->num_steps;
+	memmove(saved_steps, bls->steps,
+			saved_num * sizeof(saved_steps[0]));
+
+	for (i = 0; i < wam->count; i++) {
+		const struct workaround *wa = &wam->registry[i];
+
+		if (!wa->enabled)
+			continue;
+		if (!wa->is_applicable || !wa->apply) {
+			memmove(bls->steps, saved_steps,
+					saved_num * sizeof(saved_steps[0]));
+			*bls->num_steps = saved_num;
+			return WAM_INTERNAL_ERROR;
+		}
+		if (!wa->is_applicable(bls, ctx))
+			continue;
+		result = wa->apply(bls, ctx);
+		if (result != WAM_OK ||
+				*bls->num_steps > MAX_HWSS_BLOCK_SEQUENCE_SIZE) {
+			memmove(bls->steps, saved_steps,
+					saved_num * sizeof(saved_steps[0]));
+			*bls->num_steps = saved_num;
+			if (result != WAM_OK)
+				return result;
+			return WAM_SIZE_EXCEEDED;
+		}
+	}
+
+	return WAM_OK;
+}
diff --git a/drivers/gpu/drm/amd/display/dc/workaround_manager/workaround_manager.h b/drivers/gpu/drm/amd/display/dc/workaround_manager/workaround_manager.h
new file mode 100644
index 000000000000..4cbadffd6a8b
--- /dev/null
+++ b/drivers/gpu/drm/amd/display/dc/workaround_manager/workaround_manager.h
@@ -0,0 +1,46 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright 2026 Advanced Micro Devices, Inc.
+ */
+
+#pragma once
+
+#include "bls_builder/bls_builder.h"
+
+enum workaround_manager_result {
+	WAM_OK,
+	WAM_INVALID_INPUT,
+	WAM_SIZE_EXCEEDED,
+	WAM_INTERNAL_ERROR,
+};
+
+struct workaround_context {
+	const struct dc_state *current_state;
+	const struct dc_state *target;
+	enum bls_builder_name builder_name;
+	unsigned int dcn_version;
+	const struct dc_bug_wa *bug_wa;
+	const struct dc_debug_options *debug;
+};
+
+struct workaround {
+	const char *name;
+	bool enabled;
+	bool (*is_applicable)(const struct block_sequence_state *bls,
+			const struct workaround_context *ctx);
+	enum workaround_manager_result (*apply)(
+			struct block_sequence_state *bls,
+			const struct workaround_context *ctx);
+};
+
+struct workaround_manager {
+	const struct workaround *registry;
+	unsigned int count;
+};
+
+const struct workaround_manager *dc2_workaround_manager_get(void);
+
+enum workaround_manager_result workaround_manager_apply(
+		const struct workaround_manager *wam,
+		struct block_sequence_state *bls,
+		const struct workaround_context *ctx);