drm/ttm: introduce ttm_bo_move_null

This pattern is cut-n-pasted across 4 drivers, switch it to
a WARN_ON instead, as BUG_ON is considered a bad idea usually.
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200907204630.1406528-2-airlied@gmail.com

drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c

@@ -174,24 +174,6 @@ static int amdgpu_verify_access(struct ttm_buffer_object *bo, struct file *filp)
 					  filp->private_data);
 }
 
-/**
- * amdgpu_move_null - Register memory for a buffer object
- *
- * @bo: The bo to assign the memory to
- * @new_mem: The memory to be assigned.
- *
- * Assign the memory from new_mem to the memory of the buffer object bo.
- */
-static void amdgpu_move_null(struct ttm_buffer_object *bo,
-			     struct ttm_resource *new_mem)
-{
-	struct ttm_resource *old_mem = &bo->mem;
-
-	BUG_ON(old_mem->mm_node != NULL);
-	*old_mem = *new_mem;
-	new_mem->mm_node = NULL;
-}
-
 /**
  * amdgpu_mm_node_addr - Compute the GPU relative offset of a GTT buffer.
  *
@@ -676,7 +658,7 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
 	adev = amdgpu_ttm_adev(bo->bdev);
 
 	if (old_mem->mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
-		amdgpu_move_null(bo, new_mem);
+		ttm_bo_move_null(bo, new_mem);
 		return 0;
 	}
 	if ((old_mem->mem_type == TTM_PL_TT &&
@@ -684,7 +666,7 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
 	    (old_mem->mem_type == TTM_PL_SYSTEM &&
 	     new_mem->mem_type == TTM_PL_TT)) {
 		/* bind is enough */
-		amdgpu_move_null(bo, new_mem);
+		ttm_bo_move_null(bo, new_mem);
 		return 0;
 	}
 	if (old_mem->mem_type == AMDGPU_PL_GDS ||
@@ -694,7 +676,7 @@ static int amdgpu_bo_move(struct ttm_buffer_object *bo, bool evict,
 	    new_mem->mem_type == AMDGPU_PL_GWS ||
 	    new_mem->mem_type == AMDGPU_PL_OA) {
 		/* Nothing to save here */
-		amdgpu_move_null(bo, new_mem);
+		ttm_bo_move_null(bo, new_mem);
 		return 0;
 	}
 

drivers/gpu/drm/nouveau/nouveau_bo.c

@@ -993,9 +993,7 @@ nouveau_bo_move(struct ttm_buffer_object *bo, bool evict,
 
 	/* Fake bo copy. */
 	if (old_reg->mem_type == TTM_PL_SYSTEM && !bo->ttm) {
-		BUG_ON(bo->mem.mm_node != NULL);
-		bo->mem = *new_reg;
-		new_reg->mm_node = NULL;
+		ttm_bo_move_null(bo, new_reg);
 		goto out;
 	}
 

drivers/gpu/drm/qxl/qxl_ttm.c

@@ -158,16 +158,6 @@ static struct ttm_tt *qxl_ttm_tt_create(struct ttm_buffer_object *bo,
 	return &gtt->ttm;
 }
 
-static void qxl_move_null(struct ttm_buffer_object *bo,
-			     struct ttm_resource *new_mem)
-{
-	struct ttm_resource *old_mem = &bo->mem;
-
-	BUG_ON(old_mem->mm_node != NULL);
-	*old_mem = *new_mem;
-	new_mem->mm_node = NULL;
-}
-
 static int qxl_bo_move(struct ttm_buffer_object *bo, bool evict,
 		       struct ttm_operation_ctx *ctx,
 		       struct ttm_resource *new_mem)
@@ -180,7 +170,7 @@ static int qxl_bo_move(struct ttm_buffer_object *bo, bool evict,
 		return ret;
 
 	if (old_mem->mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
-		qxl_move_null(bo, new_mem);
+		ttm_bo_move_null(bo, new_mem);
 		return 0;
 	}
 	return ttm_bo_move_memcpy(bo, ctx, new_mem);

drivers/gpu/drm/radeon/radeon_ttm.c

@@ -148,16 +148,6 @@ static int radeon_verify_access(struct ttm_buffer_object *bo, struct file *filp)
 					  filp->private_data);
 }
 
-static void radeon_move_null(struct ttm_buffer_object *bo,
-			     struct ttm_resource *new_mem)
-{
-	struct ttm_resource *old_mem = &bo->mem;
-
-	BUG_ON(old_mem->mm_node != NULL);
-	*old_mem = *new_mem;
-	new_mem->mm_node = NULL;
-}
-
 static int radeon_move_blit(struct ttm_buffer_object *bo,
 			bool evict, bool no_wait_gpu,
 			struct ttm_resource *new_mem,
@@ -316,7 +306,7 @@ static int radeon_bo_move(struct ttm_buffer_object *bo, bool evict,
 
 	rdev = radeon_get_rdev(bo->bdev);
 	if (old_mem->mem_type == TTM_PL_SYSTEM && bo->ttm == NULL) {
-		radeon_move_null(bo, new_mem);
+		ttm_bo_move_null(bo, new_mem);
 		return 0;
 	}
 	if ((old_mem->mem_type == TTM_PL_TT &&
@@ -324,7 +314,7 @@ static int radeon_bo_move(struct ttm_buffer_object *bo, bool evict,
 	    (old_mem->mem_type == TTM_PL_SYSTEM &&
 	     new_mem->mem_type == TTM_PL_TT)) {
 		/* bind is enough */
-		radeon_move_null(bo, new_mem);
+		ttm_bo_move_null(bo, new_mem);
 		return 0;
 	}
 	if (!rdev->ring[radeon_copy_ring_index(rdev)].ready ||

include/drm/ttm/ttm_bo_driver.h

@@ -520,6 +520,23 @@ static inline void ttm_bo_move_to_lru_tail_unlocked(struct ttm_buffer_object *bo
 	spin_unlock(&ttm_bo_glob.lru_lock);
 }
 
+/**
+ * ttm_bo_move_null = assign memory for a buffer object.
+ * @bo: The bo to assign the memory to
+ * @new_mem: The memory to be assigned.
+ *
+ * Assign the memory from new_mem to the memory of the buffer object bo.
+ */
+static inline void ttm_bo_move_null(struct ttm_buffer_object *bo,
+				    struct ttm_resource *new_mem)
+{
+	struct ttm_resource *old_mem = &bo->mem;
+
+	WARN_ON(old_mem->mm_node != NULL);
+	*old_mem = *new_mem;
+	new_mem->mm_node = NULL;
+}
+
 /**
  * ttm_bo_unreserve
  *