drm/amdgpu: Set TTM_PAGE_FLAG_SG earlier for userprt BOs

Because TTM do page counting on userptr BOs which is actually not
needed. To avoid that, lets set TTM_PAGE_FLAG_SG after tt_create and
before tt_populate.
Signed-off-by: xinhui pan <xinhui.pan@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -1129,8 +1129,6 @@ static int amdgpu_ttm_tt_populate(struct ttm_device *bdev,
 		ttm->sg = kzalloc(sizeof(struct sg_table), GFP_KERNEL);
 		if (!ttm->sg)
 			return -ENOMEM;
-
-		ttm->page_flags |= TTM_PAGE_FLAG_SG;
 		return 0;
 	}
 
@@ -1156,7 +1154,6 @@ static void amdgpu_ttm_tt_unpopulate(struct ttm_device *bdev,
 		amdgpu_ttm_tt_set_user_pages(ttm, NULL);
 		kfree(ttm->sg);
 		ttm->sg = NULL;
-		ttm->page_flags &= ~TTM_PAGE_FLAG_SG;
 		return;
 	}
 
@@ -1190,6 +1187,9 @@ int amdgpu_ttm_tt_set_userptr(struct ttm_buffer_object *bo,
 			return -ENOMEM;
 	}
 
+	/* Set TTM_PAGE_FLAG_SG before populate but after create. */
+	bo->ttm->page_flags |= TTM_PAGE_FLAG_SG;
+
 	gtt = (void *)bo->ttm;
 	gtt->userptr = addr;
 	gtt->userflags = flags;