Re: [PATCH v3 23/34] dmaengine: timb_dma: route callbacks via channel BH

[Frank Li]

On Mon, Aug 10, 2026 at 11:09:24AM -0700, Allen Pais wrote:
> Schedule per-channel BH work for completions so callbacks run through
> the dma_chan deferral mechanism while keeping the controller tasklet for
> IRQ handling.
>
> Signed-off-by: Allen Pais <allen.lkml@xxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/dma/timb_dma.c | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/dma/timb_dma.c b/drivers/dma/timb_dma.c
> index 4fc5119854ec..5a2374aab02a 100644
> --- a/drivers/dma/timb_dma.c
> +++ b/drivers/dma/timb_dma.c
> @@ -438,6 +438,8 @@ static void td_free_chan_resources(struct dma_chan *chan)
>
>  	dev_dbg(chan2dev(chan), "%s: Entry\n", __func__);
>
> +	dmaengine_kill_bh(&td_chan->chan);
> +
>  	/* check that all descriptors are free */
>  	BUG_ON(!list_empty(&td_chan->active_list));
>  	BUG_ON(!list_empty(&td_chan->queue));
> @@ -580,17 +582,25 @@ static void td_tasklet(struct tasklet_struct *t)
>  	for (i = 0; i < td->dma.chancnt; i++)
>  		if (ipr & (1 << i)) {
>  			struct timb_dma_chan *td_chan = td->channels + i;
> -			spin_lock(&td_chan->lock);
> -			__td_finish(td_chan);
> -			if (!list_empty(&td_chan->queue))
> -				__td_start_next(td_chan);
> -			spin_unlock(&td_chan->lock);
> +			dmaengine_schedule_bh(&td_chan->chan);
>  		}
>
>  	ier = __td_ier_mask(td);
>  	iowrite32(ier, td->membase + TIMBDMA_IER);
>  }
>
> +static void timb_dma_chan_bh(struct dma_chan *chan)
> +{
> +	struct timb_dma_chan *td_chan = container_of(chan, struct timb_dma_chan,
> +						     chan);
> +
> +	spin_lock(&td_chan->lock);
> +	__td_finish(td_chan);
> +	if (!list_empty(&td_chan->queue))
> +		__td_start_next(td_chan);
> +	spin_unlock(&td_chan->lock);
> +}
> +
>
>  static irqreturn_t td_irq(int irq, void *devid)
>  {
> @@ -697,6 +707,7 @@ static int td_probe(struct platform_device *pdev)
>  		INIT_LIST_HEAD(&td_chan->active_list);
>  		INIT_LIST_HEAD(&td_chan->queue);
>  		INIT_LIST_HEAD(&td_chan->free_list);
> +		dmaengine_init_bh(&td_chan->chan, timb_dma_chan_bh);
>
>  		td_chan->descs = pchan->descriptors;
>  		td_chan->desc_elems = pchan->descriptor_elements;
> --
> 2.43.0
>