Re: [PATCH v2 1/2] dmaengine: fsl-edma: Implement device_prep_peripheral_dma_vec

[Frank Li]

On Wed, May 06, 2026 at 04:10:35PM +0200, Benoît Monin wrote:
> Add implementation of .device_prep_peripheral_dma_vec() callback to setup
> a scatter/gather DMA transfer from an array of dma_vec structures. Setup
> a cyclic transfer if the DMA_PREP_REPEAT flag is set.
>
> Signed-off-by: Benoît Monin <benoit.monin@xxxxxxxxxxx>
> ---
>  drivers/dma/fsl-edma-common.c | 110 ++++++++++++++++++++++++++++++++++++++++++
>  drivers/dma/fsl-edma-common.h |   4 ++
>  drivers/dma/fsl-edma-main.c   |   2 +
>  3 files changed, 116 insertions(+)
>
> diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
> index bb7531c456df..26a5ecf493b9 100644
> --- a/drivers/dma/fsl-edma-common.c
> +++ b/drivers/dma/fsl-edma-common.c
> @@ -673,6 +673,116 @@ struct dma_async_tx_descriptor *fsl_edma_prep_dma_cyclic(
>  	return vchan_tx_prep(&fsl_chan->vchan, &fsl_desc->vdesc, flags);
>  }
>
> +struct dma_async_tx_descriptor *fsl_edma_prep_peripheral_dma_vec(
> +		struct dma_chan *chan, const struct dma_vec *vecs,
> +		size_t nb, enum dma_transfer_direction direction,
> +		unsigned long flags)

struct dma_async_tx_descriptor *
fsl_edma_prep_peripheral_dma_vec(struct dma_chan *chan, ...
				 size_t nb
				 ...

> +{
> +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> +	struct fsl_edma_desc *fsl_desc;
> +	dma_addr_t src_addr, dst_addr, last_sg;

Keep revise christmas tree order, switch both lines.

> +	u16 soff, doff, iter;
> +	u32 nbytes;
> +	int i;
> +
> +	if (!is_slave_direction(direction))
> +		return NULL;
> +
> +	if (!fsl_edma_prep_slave_dma(fsl_chan, direction))
> +		return NULL;
> +
> +	fsl_desc = fsl_edma_alloc_desc(fsl_chan, nb);
> +	if (!fsl_desc)
> +		return NULL;
> +	fsl_desc->iscyclic = flags & DMA_PREP_REPEAT;
> +	fsl_desc->dirn = direction;
> +
> +	if (direction == DMA_MEM_TO_DEV) {
> +		if (!fsl_chan->cfg.src_addr_width)
> +			fsl_chan->cfg.src_addr_width = fsl_chan->cfg.dst_addr_width;
> +		fsl_chan->attr =
> +			fsl_edma_get_tcd_attr(fsl_chan->cfg.src_addr_width,
> +					      fsl_chan->cfg.dst_addr_width);
> +		nbytes = fsl_chan->cfg.dst_addr_width *
> +			fsl_chan->cfg.dst_maxburst;

This file already use 100 column, keep it to one line. check other nbtyes.

> +	} else {
> +		if (!fsl_chan->cfg.dst_addr_width)
> +			fsl_chan->cfg.dst_addr_width = fsl_chan->cfg.src_addr_width;
> +		fsl_chan->attr =
> +			fsl_edma_get_tcd_attr(fsl_chan->cfg.src_addr_width,
> +					      fsl_chan->cfg.dst_addr_width);
> +		nbytes = fsl_chan->cfg.src_addr_width *
> +			fsl_chan->cfg.src_maxburst;
> +	}
> +
> +	for (i = 0; i < nb; i++) {
> +		if (direction == DMA_MEM_TO_DEV) {
> +			src_addr = vecs[i].addr;
> +			dst_addr = fsl_chan->dma_dev_addr;
> +			soff = fsl_chan->cfg.dst_addr_width;
> +			doff = 0;
> +		} else if (direction == DMA_DEV_TO_MEM) {
> +			src_addr = fsl_chan->dma_dev_addr;
> +			dst_addr = vecs[i].addr;
> +			soff = 0;
> +			doff = fsl_chan->cfg.src_addr_width;
> +		} else {
> +			/* DMA_DEV_TO_DEV */
> +			src_addr = fsl_chan->cfg.src_addr;
> +			dst_addr = fsl_chan->cfg.dst_addr;
> +			soff = 0;
> +			doff = 0;
> +		}
> +
> +		/*
> +		 * Choose the suitable burst length if dma_vec length is not
> +		 * multiple of burst length so that the whole transfer length is
> +		 * multiple of minor loop(burst length).
> +		 */
> +		if (vecs[i].len % nbytes) {
> +			u32 width = (direction == DMA_DEV_TO_MEM) ? doff : soff;
> +			u32 burst = (direction == DMA_DEV_TO_MEM) ?
> +						fsl_chan->cfg.src_maxburst :
> +						fsl_chan->cfg.dst_maxburst;
> +			int j;
> +
> +			for (j = burst; j > 1; j--) {
> +				if (!(vecs[i].len % (j * width))) {
> +					nbytes = j * width;
> +					break;
> +				}
> +			}
> +			/* Set burst size as 1 if there's no suitable one */
> +			if (j == 1)
> +				nbytes = width;
> +		}

add empty line here!

Frank
>
> --
> 2.54.0
>