dmaengine: omap-dma: move barrier to omap_dma_start_desc()

We don't need to issue a barrier for every segment of a DMA transfer;
doing this just once per descriptor will do.

Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
index 49609275b2e7..49b303296d75 100644
--- a/drivers/dma/omap-dma.c
+++ b/drivers/dma/omap-dma.c
@@ -195,7 +195,6 @@ static void omap_dma_start(struct omap_chan *c, struct omap_desc *d)
 
         val = c->plat->dma_read(CCR, c->dma_ch);
         val |= CCR_ENABLE;
-        mb();
         c->plat->dma_write(val, CCR, c->dma_ch);
 }
 
@@ -301,6 +300,13 @@ static void omap_dma_start_desc(struct omap_chan *c)
         c->desc = d = to_omap_dma_desc(&vd->tx);
         c->sgidx = 0;
 
+        /*
+         * This provides the necessary barrier to ensure data held in
+         * DMA coherent memory is visible to the DMA engine prior to
+         * the transfer starting.
+         */
+        mb();
+
         c->plat->dma_write(d->ccr, CCR, c->dma_ch);
         if (dma_omap1())
                 c->plat->dma_write(d->ccr >> 16, CCR2, c->dma_ch);