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

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Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=0bc254257bfd9b25f64a68b719ee70a303b6d051
Commit:     0bc254257bfd9b25f64a68b719ee70a303b6d051
Parent:     a3483353ca4e6dbeef2ed62ebed01af109b5b27a
Author:     Thomas Hellstrom <thellstrom at vmware.com>
AuthorDate: Sun Nov 17 23:30:38 2013 -0800
Committer:  Thomas Hellstrom <thellstrom at vmware.com>
CommitDate: Wed Nov 20 03:43:28 2013 -0800

    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 at vmware.com>
    Reviewed-by: Jakob Bornecrantz <jakob 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.