Am 19.05.21 um 10:24 schrieb Daniel Vetter:
Motivated because I got confused and Christian confirmed why this
works. I think this is non-obvious enough that it merits a slightly
longer comment.
Cc: Christian König <ckoenig.leichtzumerken@xxxxxxxxx>
Cc: Christian Koenig <christian.koenig@xxxxxxx>
Cc: Huang Rui <ray.huang@xxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
---
drivers/gpu/drm/ttm/ttm_bo.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index ca1b098b6a56..51a94fd63bd7 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -682,7 +682,9 @@ int ttm_mem_evict_first(struct ttm_device *bdev,
}
/*
- * Add the last move fence to the BO and reserve a new shared slot.
+ * Add the last move fence to the BO and reserve a new shared slot. We only use
+ * a shared slot to avoid unecessary sync and rely on the subsequent bo move to
+ * either stall or use an exclusive fence respectively set bo->moving.
*/
static int ttm_bo_add_move_fence(struct ttm_buffer_object *bo,
struct ttm_resource_manager *man,
