Nouveau - Oct 2020 - [PATCH 25/65] drm/nouveau: Drop mutex_lock_nested for atomic

Purely conjecture, but I think the original locking inversion with the
legacy page flip code between flipping and ttm's bo move function
shoudn't exist anymore with atomic: With atomic the bo pinning and
actual modeset commit is completely separated in the code patsh.

This annotation was originally added in

commit 060810d7abaabcab282e062c595871d661561400
Author: Ben Skeggs <bskeggs at redhat.com>
Date:   Mon Jul 8 14:15:51 2013 +1000

    drm/nouveau: fix locking issues in page flipping paths

due to

commit b580c9e2b7ba5030a795aa2fb73b796523d65a78
Author: Maarten Lankhorst <m.b.lankhorst at gmail.com>
Date:   Thu Jun 27 13:48:18 2013 +0200

    drm/nouveau: make flipping lockdep safe

Reviewed-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
Cc: Maarten Lankhorst <m.b.lankhorst at gmail.com>
Cc: Ben Skeggs <bskeggs at redhat.com>
Cc: Dave Airlie <airlied at gmail.com>
Cc: nouveau at lists.freedesktop.org
---
I might be totally wrong, so this definitely needs testing :-)

Cheers, Daniel
---
 drivers/gpu/drm/nouveau/nouveau_bo.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_bo.c
b/drivers/gpu/drm/nouveau/nouveau_bo.c
index 70b6f3b1ae85..c04a808664f8 100644
--- a/drivers/gpu/drm/nouveau/nouveau_bo.c
+++ b/drivers/gpu/drm/nouveau/nouveau_bo.c
@@ -775,7 +775,10 @@ nouveau_bo_move_m2mf(struct ttm_buffer_object *bo, int
evict,
 			return ret;
 	}
 
-	mutex_lock_nested(&cli->mutex, SINGLE_DEPTH_NESTING);
+	if (drm_drv_uses_atomic_modeset(drm->dev))
+		mutex_lock(&cli->mutex);
+	else
+		mutex_lock_nested(&cli->mutex, SINGLE_DEPTH_NESTING);
 	ret = nouveau_fence_sync(nouveau_bo(bo), chan, true, ctx->interruptible);
 	if (ret == 0) {
 		ret = drm->ttm.move(chan, bo, &bo->mem, new_reg);
-- 
2.28.0