1 files changed, 14 insertions, 0 deletions

diff --git a/arch/arm/plat-omap/dma.c b/arch/arm/plat-omap/dma.c
index ecdb3da0dea9..c58d896cd5c3 100644
--- a/arch/arm/plat-omap/dma.c
+++ b/arch/arm/plat-omap/dma.c
@@ -916,6 +916,13 @@ void omap_start_dma(int lch)
                         l |= OMAP_DMA_CCR_BUFFERING_DISABLE;
         l |= OMAP_DMA_CCR_EN;
 
+        /*
+         * As dma_write() uses IO accessors which are weakly ordered, there
+         * is no guarantee that data in coherent DMA memory will be visible
+         * to the DMA device.  Add a memory barrier here to ensure that any
+         * such data is visible prior to enabling DMA.
+         */
+        mb();
         p->dma_write(l, CCR, lch);
 
         dma_chan[lch].flags |= OMAP_DMA_ACTIVE;
@@ -965,6 +972,13 @@ void omap_stop_dma(int lch)
                 p->dma_write(l, CCR, lch);
         }
 
+        /*
+         * Ensure that data transferred by DMA is visible to any access
+         * after DMA has been disabled.  This is important for coherent
+         * DMA regions.
+         */
+        mb();
+
         if (!omap_dma_in_1510_mode() && dma_chan[lch].next_lch != -1) {
                 int next_lch, cur_lch = lch;
                 char dma_chan_link_map[dma_lch_count];