于 2012年10月25日 12:18, Vinod Koul 写道:
+ +static int mxs_auart_dma_tx(struct mxs_auart_port *s, int size) +{ + struct dma_async_tx_descriptor *desc; + struct scatterlist *sgl =&s->tx_sgl; + struct dma_chan *channel = s->tx_dma_chan; + u32 pio; + + /* [1] : send PIO. Note, the first pio word is CTRL1. */ + pio = AUART_CTRL1_XFER_COUNT(size); + desc = dmaengine_prep_slave_sg(channel, (struct scatterlist *)&pio, + 1, DMA_TRANS_NONE, 0);this seems like a hack. API expects a scatterlist as argument. Same thing about direction, NONE doesnt mean anything for dma transfer.
It's not a hack. this DMA descriptor is used to set the registers. Please see the code in drivers/dma/mxs-dma.c:mxs_dam_prep_slave_sg().
+ if (!desc) { + dev_err(s->dev, "step 1 error\n"); + return -EINVAL; + } + + /* [2] : set DMA buffer. */ + sg_init_one(sgl, s->tx_dma_buf, size); + dma_map_sg(s->dev, sgl, 1, DMA_TO_DEVICE); + desc = dmaengine_prep_slave_sg(channel, sgl, + 1, DMA_MEM_TO_DEV, DMA_PREP_INTERRUPT | DMA_CTRL_ACK); + if (!desc) { + dev_err(s->dev, "step 2 error\n"); + return -EINVAL; + } + + /* [3] : submit the DMA */ + desc->callback = dma_tx_callback; + desc->callback_param = s; + dmaengine_submit(desc); + dma_async_issue_pending(channel); + return 0; +} + +static bool mxs_auart_dma_filter(struct dma_chan *chan, void *param) +{ + struct mxs_auart_port *s = param; + + if (!mxs_dma_is_apbx(chan)) + return false; + + if (s->dma_channel == chan->chan_id) { + chan->private =&s->dma_data;dont use chan->private. You need to dmaengine_slave_config API
please see the drivers/dma/mxs-dma.c:mxs_dam_alloc_chan_resoures(). The mxs-dma driver uses ->private to store the channel interrupt number. thanks Huang Shijie
+ return true; + } + return false; +} +
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