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

[Thomas Hellstrom]

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 at vmware.com>
---
 drivers/gpu/drm/ttm/ttm_bo_util.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index 4834c46..15b86a9 100644
--- 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.
-- 
1.7.10.4