? 2012?10?25? 12:18, Vinod Koul ??:

quoted

+
+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().

quoted

+	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

quoted

+		return true;
+	}
+	return false;
+}
+