diff options
Diffstat (limited to 'drivers/dma/mxs-dma.c')
| -rw-r--r-- | drivers/dma/mxs-dma.c | 32 |
1 files changed, 28 insertions, 4 deletions
diff --git a/drivers/dma/mxs-dma.c b/drivers/dma/mxs-dma.c index 0afcedbe247..0ddfd30b56a 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; } } } |