async_tx: remove walk of tx->parent chain in dma_wait_for_async_tx

[safe/jmp/linux-2.6] / drivers / dma / dmaengine.c

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index 6781e8f..e002e0e 100644 (file)
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -934,49 +934,24 @@ EXPORT_SYMBOL(dma_async_tx_descriptor_init);
 
 /* dma_wait_for_async_tx - spin wait for a transaction to complete
  * @tx: in-flight transaction to wait on
- *
- * This routine assumes that tx was obtained from a call to async_memcpy,
- * async_xor, async_memset, etc which ensures that tx is "in-flight" (prepped
- * and submitted).  Walking the parent chain is only meant to cover for DMA
- * drivers that do not implement the DMA_INTERRUPT capability and may race with
- * the driver's descriptor cleanup routine.
  */
 enum dma_status
 dma_wait_for_async_tx(struct dma_async_tx_descriptor *tx)
 {
-       enum dma_status status;
-       struct dma_async_tx_descriptor *iter;
-       struct dma_async_tx_descriptor *parent;
+       unsigned long dma_sync_wait_timeout = jiffies + msecs_to_jiffies(5000);
 
        if (!tx)
                return DMA_SUCCESS;
 
-       WARN_ONCE(tx->parent, "%s: speculatively walking dependency chain for"
-                 " %s\n", __func__, dma_chan_name(tx->chan));
-
-       /* poll through the dependency chain, return when tx is complete */
-       do {
-               iter = tx;
-
-               /* find the root of the unsubmitted dependency chain */
-               do {
-                       parent = iter->parent;
-                       if (!parent)
-                               break;
-                       else
-                               iter = parent;
-               } while (parent);
-
-               /* there is a small window for ->parent == NULL and
-                * ->cookie == -EBUSY
-                */
-               while (iter->cookie == -EBUSY)
-                       cpu_relax();
-
-               status = dma_sync_wait(iter->chan, iter->cookie);
-       } while (status == DMA_IN_PROGRESS || (iter != tx));
-
-       return status;
+       while (tx->cookie == -EBUSY) {
+               if (time_after_eq(jiffies, dma_sync_wait_timeout)) {
+                       pr_err("%s timeout waiting for descriptor submission\n",
+                               __func__);
+                       return DMA_ERROR;
+               }
+               cpu_relax();
+       }
+       return dma_sync_wait(tx->chan, tx->cookie);
 }
 EXPORT_SYMBOL_GPL(dma_wait_for_async_tx);