Re: [PATCH 3/5] dma: dma-axi-dmac: add helper for getting next desc

[Frank Li <Frank.li@nxp.com>]

On Tue, Jan 27, 2026 at 02:28:24PM +0000, Nuno Sá wrote:
> Add a new helper for getting the next valid struct axi_dmac_desc. This
> will be extended in follow up patches to support to gracefully terminate
> cyclic transfers.
>
> Signed-off-by: Nuno Sá <nuno.sa@analog.com>
> ---
>  drivers/dma/dma-axi-dmac.c | 33 +++++++++++++++++++++++----------
>  1 file changed, 23 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
> index b083b6176593..3984236717a6 100644
> --- a/drivers/dma/dma-axi-dmac.c
> +++ b/drivers/dma/dma-axi-dmac.c
> @@ -227,10 +227,29 @@ static bool axi_dmac_check_addr(struct axi_dmac_chan *chan, dma_addr_t addr)
>  	return true;
>  }
>
> +static struct axi_dmac_desc *axi_dmac_get_next_desc(struct axi_dmac *dmac,
> +						    struct axi_dmac_chan *chan)

Nit: if need respin,

static struct axi_dmac_desc *
axi_dmac_get_next_desc(struct axi_dmac *dmac, struct axi_dmac_chan *chan)

This is also fine.

Reviewed-by: Frank Li <Frank.Li@nxp.com>
> +{
> +	struct virt_dma_desc *vdesc;
> +	struct axi_dmac_desc *desc;
> +
> +	if (chan->next_desc)
> +		return chan->next_desc;
> +
> +	vdesc = vchan_next_desc(&chan->vchan);
> +	if (!vdesc)
> +		return NULL;
> +
> +	list_move_tail(&vdesc->node, &chan->active_descs);
> +	desc = to_axi_dmac_desc(vdesc);
> +	chan->next_desc = desc;
> +
> +	return desc;
> +}
> +
>  static void axi_dmac_start_transfer(struct axi_dmac_chan *chan)
>  {
>  	struct axi_dmac *dmac = chan_to_axi_dmac(chan);
> -	struct virt_dma_desc *vdesc;
>  	struct axi_dmac_desc *desc;
>  	struct axi_dmac_sg *sg;
>  	unsigned int flags = 0;
> @@ -240,16 +259,10 @@ static void axi_dmac_start_transfer(struct axi_dmac_chan *chan)
>  	if (val) /* Queue is full, wait for the next SOT IRQ */
>  		return;
>
> -	desc = chan->next_desc;
> +	desc = axi_dmac_get_next_desc(dmac, chan);
> +	if (!desc)
> +		return;
>
> -	if (!desc) {
> -		vdesc = vchan_next_desc(&chan->vchan);
> -		if (!vdesc)
> -			return;
> -		list_move_tail(&vdesc->node, &chan->active_descs);
> -		desc = to_axi_dmac_desc(vdesc);
> -		chan->next_desc = desc;
> -	}
>  	sg = &desc->sg[desc->num_submitted];
>
>  	/* Already queued in cyclic mode. Wait for it to finish */
>
> --
> 2.52.0
>