dma: mxs-dma: make mxs_dma_prep_slave_sg() multi user safe

Using a static variable for counting the number of CCWs attached to
a DMA channel when appending a new descriptor is not multi user safe.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
index b0e6ac3e09aa..1b4c6be3aacb 100644
--- a/drivers/dma/mxs-dma.c
+++ b/drivers/dma/mxs-dma.c
@@ -111,6 +111,7 @@ struct mxs_dma_chan {
         int                             chan_irq;
         struct mxs_dma_ccw              *ccw;
         dma_addr_t                      ccw_phys;
+        int                             desc_count;
         dma_cookie_t                    last_completed;
         enum dma_status                 status;
         unsigned int                    flags;
@@ -386,7 +387,7 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
         struct scatterlist *sg;
         int i, j;
         u32 *pio;
-        static int idx;
+        int idx = append ? mxs_chan->desc_count : 0;
 
         if (mxs_chan->status == DMA_IN_PROGRESS && !append)
                 return NULL;
@@ -462,6 +463,7 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
                         }
                 }
         }
+        mxs_chan->desc_count = idx;
 
         return &mxs_chan->desc;
 
@@ -523,6 +525,7 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_dma_cyclic(
 
                 i++;
         }
+        mxs_chan->desc_count = i;
 
         return &mxs_chan->desc;