[PATCH] drm/amd/display: fix usage of DC_FPU_{BEGIN,END} with PREEMPT_RT

[Bert Karwatzki]

On PREEMPT_RT kernels kvzalloc_obj() can sleep because spin_lock is
converted to rt_mutex. dc_create_plane_state() can be called while
inside an FPU-guarded region, resuling in "scheduling while atomic"
errors on PREEMPT_RT kernels.
 Fix this by calling kvzalloc_obj() with DC_RUN_WITH_PREEMPTION_ENABLED().
Also fix the error path in dc_create_stream_for_sink().

Fixes: 3539437f354b ("drm/amd/display: Move FPU Guards From DML To DC - Part 1")
Link: https://lore.kernel.org/lkml/20260723123449.6494-1-spasswolf@xxxxxx/

Signed-off-by: Bert Karwatzki <spasswolf@xxxxxx>
---
 drivers/gpu/drm/amd/display/dc/core/dc_stream.c  | 2 +-
 drivers/gpu/drm/amd/display/dc/core/dc_surface.c | 5 +++--
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
index cdcf140bc1bb..accad9e20e88 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_stream.c
@@ -229,7 +229,7 @@ struct dc_stream_state *dc_create_stream_for_sink(
 
 fail:
 	if (stream)
-		kfree(stream);
+		DC_RUN_WITH_PREEMPTION_ENABLED(kfree(stream));
 
 	return NULL;
 }
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc_surface.c b/drivers/gpu/drm/amd/display/dc/core/dc_surface.c
index 88e825a6582c..f4eb021711cb 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc_surface.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc_surface.c
@@ -33,6 +33,7 @@
 #include "dpp.h"
 
 #include "dc_plane_priv.h"
+#include "dc_fpu.h"
 
 /*******************************************************************************
  * Private functions
@@ -85,8 +86,8 @@ uint8_t  dc_plane_get_pipe_mask(struct dc_state *dc_state, const struct dc_plane
  ******************************************************************************/
 struct dc_plane_state *dc_create_plane_state(const struct dc *dc)
 {
-	struct dc_plane_state *plane_state = kvzalloc_obj(*plane_state,
-							  GFP_ATOMIC);
+	struct dc_plane_state *plane_state;
+	DC_RUN_WITH_PREEMPTION_ENABLED(plane_state = kvzalloc_obj(*plane_state, GFP_ATOMIC));
 
 	if (NULL == plane_state)
 		return NULL;
-- 
2.55.0

Added compile fix (by Mikhail Gavrilov) for CONFIG_DRM_AMD_DC_FP=n to
the patch for linux-next. Compile tested with arm64/clang on debian sid.

Bert Karwatzki