1 files changed, 28 insertions, 4 deletions

diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c
index 0afcedbe2471..0ddfd30b56ad 100644
--- a/drivers/dma/mxs-dma.c
+++ b/drivers/dma/mxs-dma.c
@@ -349,10 +349,32 @@ static void mxs_dma_free_chan_resources(struct dma_chan *chan)
         clk_disable_unprepare(mxs_dma->clk);
 }
 
+/*
+ * How to use the flags for ->device_prep_slave_sg() :
+ *    [1] If there is only one DMA command in the DMA chain, the code should be:
+ *            ......
+ *            ->device_prep_slave_sg(DMA_CTRL_ACK);
+ *            ......
+ *    [2] If there are two DMA commands in the DMA chain, the code should be
+ *            ......
+ *            ->device_prep_slave_sg(0);
+ *            ......
+ *            ->device_prep_slave_sg(DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
+ *            ......
+ *    [3] If there are more than two DMA commands in the DMA chain, the code
+ *        should be:
+ *            ......
+ *            ->device_prep_slave_sg(0);                                // First
+ *            ......
+ *            ->device_prep_slave_sg(DMA_PREP_INTERRUPT [| DMA_CTRL_ACK]);
+ *            ......
+ *            ->device_prep_slave_sg(DMA_PREP_INTERRUPT | DMA_CTRL_ACK); // Last
+ *            ......
+ */
 static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
                 struct dma_chan *chan, struct scatterlist *sgl,
                 unsigned int sg_len, enum dma_transfer_direction direction,
-                unsigned long append)
+                unsigned long flags)
 {
         struct mxs_dma_chan *mxs_chan = to_mxs_dma_chan(chan);
         struct mxs_dma_engine *mxs_dma = mxs_chan->mxs_dma;
@@ -360,6 +382,7 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
         struct scatterlist *sg;
         int i, j;
         u32 *pio;
+        bool append = flags & DMA_PREP_INTERRUPT;
         int idx = append ? mxs_chan->desc_count : 0;
 
         if (mxs_chan->status == DMA_IN_PROGRESS && !append)
@@ -386,7 +409,6 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
                 ccw->bits |= CCW_CHAIN;
                 ccw->bits &= ~CCW_IRQ;
                 ccw->bits &= ~CCW_DEC_SEM;
-                ccw->bits &= ~CCW_WAIT4END;
         } else {
                 idx = 0;
         }
@@ -401,7 +423,8 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
                 ccw->bits = 0;
                 ccw->bits |= CCW_IRQ;
                 ccw->bits |= CCW_DEC_SEM;
-                ccw->bits |= CCW_WAIT4END;
+                if (flags & DMA_CTRL_ACK)
+                        ccw->bits |= CCW_WAIT4END;
                 ccw->bits |= CCW_HALT_ON_TERM;
                 ccw->bits |= CCW_TERM_FLUSH;
                 ccw->bits |= BF_CCW(sg_len, PIO_NUM);
@@ -432,7 +455,8 @@ static struct dma_async_tx_descriptor *mxs_dma_prep_slave_sg(
                                 ccw->bits &= ~CCW_CHAIN;
                                 ccw->bits |= CCW_IRQ;
                                 ccw->bits |= CCW_DEC_SEM;
-                                ccw->bits |= CCW_WAIT4END;
+                                if (flags & DMA_CTRL_ACK)
+                                        ccw->bits |= CCW_WAIT4END;
                         }
                 }
         }