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path: root/drivers/dma/mxs-dma.c
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Diffstat (limited to 'drivers/dma/mxs-dma.c')
-rw-r--r--drivers/dma/mxs-dma.c32
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;
}
}
}