dma-buf/fence: make timeout handling in fence_default_wait consistent (v2)

Kernel functions taking a timeout usually return 1 on success even
when they get a zero timeout.

v2: agd: rebase on drm-next

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chunming Zhou <david1.zhou@amd.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: http://patchwork.freedesktop.org/patch/msgid/1478553376-18575-1-git-send-email-alexander.deucher@amd.com

drivers/dma-buf/dma-fence.c

@@ -339,18 +339,20 @@ dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
  * @timeout:	[in]	timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
  *
  * Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
- * remaining timeout in jiffies on success.
+ * remaining timeout in jiffies on success. If timeout is zero the value one is
+ * returned if the fence is already signaled for consistency with other
+ * functions taking a jiffies timeout.
  */
 signed long
 dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
 {
 	struct default_wait_cb cb;
 	unsigned long flags;
-	signed long ret = timeout;
+	signed long ret = timeout ? timeout : 1;
 	bool was_set;
 
 	if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
-		return timeout;
+		return ret;
 
 	spin_lock_irqsave(fence->lock, flags);