drm/ttm: Don't move non-existing data

If ttm_bo_move_memcpy was instructed to move a non-populated ttm to
io memory, it would first populate the ttm, then move the data and then
destroy the ttm. That's stupid. However, some drivers might have relied on
this to clear io memory from old stuff. So instead of a NOP, which would
be the most efficient, just clear the destination.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 4834c463c38bdf04d02049f5ca324d152fb6f57d..15b86a94949dcb875d3cd716322875ad8c763e88 100644 (file)
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -350,10 +350,13 @@ int ttm_bo_move_memcpy(struct ttm_buffer_object *bo,
                goto out2;
 
        /*
-        * Move nonexistent data. NOP.
+        * Don't move nonexistent data. Clear destination instead.
         */
-       if (old_iomap == NULL && ttm == NULL)
+       if (old_iomap == NULL &&
+           (ttm == NULL || ttm->state == tt_unpopulated)) {
+               memset_io(new_iomap, 0, new_mem->num_pages*PAGE_SIZE);
                goto out2;
+       }
 
        /*
         * TTM might be null for moves within the same region.