--- a/sys/dev/drm/radeon/rv770_dma.c
+++ b/sys/dev/drm/radeon/rv770_dma.c
@@ -48,13 +48,14 @@
 	struct radeon_sync sync;
 	int ring_index = rdev->asic->copy.dma_ring_index;
 	struct radeon_ring *ring = &rdev->ring[ring_index];
-	u32 size_in_dw, cur_size_in_dw;
+	u64 size_in_dw;
+	u32 cur_size_in_dw;
 	int i, num_loops;
 	int r = 0;
 
 	radeon_sync_create(&sync);
 
-	size_in_dw = (num_gpu_pages << RADEON_GPU_PAGE_SHIFT) / 4;
+	size_in_dw = ((u64)num_gpu_pages << RADEON_GPU_PAGE_SHIFT) / 4;
 	num_loops = DIV_ROUND_UP(size_in_dw, 0xFFFF);
 	r = radeon_ring_lock(rdev, ring, num_loops * 5 + 8);
 	if (r) {