Re: [PATCH v3 34/34] dmaengine: switchtec: use channel BH helpers

[Frank Li]

On Mon, Aug 10, 2026 at 11:09:35AM -0700, Allen Pais wrote:
> Replace the per-channel descriptor completion tasklet with the shared
> dmaengine BH helpers. Client callbacks remain in softirq context while
> using the common scheduling and teardown mechanism.
>
> Signed-off-by: Allen Pais <allen.lkml@xxxxxxxxx>
> Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
> ---

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

>  drivers/dma/switchtec_dma.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/dma/switchtec_dma.c b/drivers/dma/switchtec_dma.c
> index 71d9868ce613..849f1f2f8105 100644
> --- a/drivers/dma/switchtec_dma.c
> +++ b/drivers/dma/switchtec_dma.c
> @@ -133,8 +133,6 @@ struct switchtec_dma_chan {
>  	/* Serialize hardware control register access */
>  	spinlock_t hw_ctrl_lock;
>
> -	struct tasklet_struct desc_task;
> -
>  	/* Serialize descriptor preparation */
>  	spinlock_t submit_lock;
>  	bool ring_active;
> @@ -584,6 +582,7 @@ static void switchtec_dma_synchronize(struct dma_chan *chan)
>
>  	int rc;
>
> +	dmaengine_kill_bh(chan);
>  	switchtec_dma_abort_desc(swdma_chan, 1);
>
>  	rc = enable_channel(swdma_chan);
> @@ -820,9 +819,10 @@ static int switchtec_dma_resume(struct dma_chan *chan)
>  	return ret;
>  }
>
> -static void switchtec_dma_desc_task(unsigned long data)
> +static void switchtec_dma_desc_task(struct dma_chan *chan)
>  {
> -	struct switchtec_dma_chan *swdma_chan = (void *)data;
> +	struct switchtec_dma_chan *swdma_chan =
> +		container_of(chan, struct switchtec_dma_chan, dma_chan);
>
>  	switchtec_dma_cleanup_completed(swdma_chan);
>  }
> @@ -832,7 +832,7 @@ static irqreturn_t switchtec_dma_isr(int irq, void *chan)
>  	struct switchtec_dma_chan *swdma_chan = chan;
>
>  	if (swdma_chan->comp_ring_active)
> -		tasklet_schedule(&swdma_chan->desc_task);
> +		dmaengine_schedule_bh(&swdma_chan->dma_chan);
>
>  	return IRQ_HANDLED;
>  }
> @@ -1041,6 +1041,7 @@ static void switchtec_dma_free_chan_resources(struct dma_chan *chan)
>  	spin_unlock_bh(&swdma_chan->complete_lock);
>
>  	switchtec_dma_chan_stop(swdma_chan);
> +	dmaengine_kill_bh(chan);
>  	switchtec_dma_abort_desc(swdma_chan, 0);
>  	switchtec_dma_free_desc(swdma_chan);
>
> @@ -1067,8 +1068,6 @@ static int switchtec_dma_chan_init(struct switchtec_dma_dev *swdma_dev,
>  	spin_lock_init(&swdma_chan->hw_ctrl_lock);
>  	spin_lock_init(&swdma_chan->submit_lock);
>  	spin_lock_init(&swdma_chan->complete_lock);
> -	tasklet_init(&swdma_chan->desc_task, switchtec_dma_desc_task,
> -		     (unsigned long)swdma_chan);
>
>  	swdma_chan->mmio_chan_fw =
>  		swdma_dev->bar + SWITCHTEC_DMAC_CHAN_CFG_STS_OFFSET +
> @@ -1116,6 +1115,7 @@ static int switchtec_dma_chan_init(struct switchtec_dma_dev *swdma_dev,
>  	chan = &swdma_chan->dma_chan;
>  	chan->device = dma;
>  	dma_cookie_init(chan);
> +	dmaengine_init_bh(chan, switchtec_dma_desc_task);
>
>  	list_add_tail(&chan->device_node, &dma->channels);
>
> @@ -1138,7 +1138,7 @@ static int switchtec_dma_chan_free(struct pci_dev *pdev,
>  	spin_unlock_bh(&swdma_chan->complete_lock);
>
>  	pci_free_irq(pdev, swdma_chan->irq, swdma_chan);
> -	tasklet_kill(&swdma_chan->desc_task);
> +	dmaengine_kill_bh(&swdma_chan->dma_chan);
>
>  	switchtec_dma_chan_stop(swdma_chan);
>
> --
> 2.43.0
>