于 2012年10月25日 14:07, Vinod Koul 写道:
On Thu, 2012-10-25 at 13:50 +0800, Huang Shijie wrote:
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().
yes it is, and also an abuse of the api.
prep_slave_sg() expects a scatter list and you are passing something
else and using DMA_TRANS_NONE to do that, which makes no sense!!!
If you have to setup your registers you need to setup based on what APIs
passed you and not by abusing.
yes. I have to setup the register. Could you told me which API is the
right API?
It seems to the mxs-dma needs a patch again.
+ 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.
And which it should not be doing. private is not supposed to be used for
passing info. If it is generic add to slave config.
Could you give me an example which do not use the private?
The imx-sdma also uses the private to pass some info.
thanks
Huang Shijie
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