dmaengine: add cpu_relax() to busy-loop in dma_sync_wait()

Removal of the busy-loop from dma_sync_wait() is not a trivial
task so just add cpu_relax() to the loop for now.

Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Dan Williams <djbw@fb.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index d37cf95987b6..242b8c0a3de8 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -267,7 +267,10 @@ enum dma_status dma_sync_wait(struct dma_chan *chan, dma_cookie_t cookie)
                         pr_err("%s: timeout!\n", __func__);
                         return DMA_ERROR;
                 }
-        } while (status == DMA_IN_PROGRESS);
+                if (status != DMA_IN_PROGRESS)
+                        break;
+                cpu_relax();
+        } while (1);
 
         return status;
 }