On Wed, 2012-10-24 at 18:27 +0800, Huang Shijie wrote:
> Only we meet the following conditions, we can enable the DMA support for
> auart:
>
> (1) We enable the DMA support in the dts file, such as
> arch/arm/boot/dts/imx28.dtsi.
>
> (2) We enable the hardware flow control.
>
> (3) We use the mx28, not the mx23. Due to hardware bug(see errata: 2836),
> we can not add the DMA support to mx23.
>
> Signed-off-by: Huang Shijie <b32955@xxxxxxxxxxxxx>
>
> #define to_auart_port(u) container_of(u, struct mxs_auart_port, port)
> +
> +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.
> + 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
> + return true;
> + }
> + return false;
> +}
> +
--
Vinod Koul
Intel Corp.
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