Re: [PATCH v3 32/34] dmaengine: hidma: defer callbacks via channel BH

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

On Mon, Aug 10, 2026 at 11:09:33AM -0700, Allen Pais wrote:
> Move descriptor callback processing out of the low-level completion
> path and schedule it through per-channel BH work. Drain that work while
> freeing channels so callbacks cannot outlive channel storage.
>
> Signed-off-by: Allen Pais <allen.lkml@gmail.com>
> ---
>  drivers/dma/qcom/hidma.c | 18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/dma/qcom/hidma.c b/drivers/dma/qcom/hidma.c
> index c939635be21d..486a2c61a9fb 100644
> --- a/drivers/dma/qcom/hidma.c
> +++ b/drivers/dma/qcom/hidma.c
> @@ -90,7 +90,13 @@ static inline struct hidma_chan *to_hidma_chan(struct dma_chan *dmach)
>
>  static void hidma_free(struct hidma_dev *dmadev)
>  {
> -	INIT_LIST_HEAD(&dmadev->ddev.channels);
> +	struct hidma_chan *mchan, *next;
> +
> +	list_for_each_entry_safe(mchan, next, &dmadev->ddev.channels,
> +				 chan.device_node) {
> +		dmaengine_kill_bh(&mchan->chan);
> +		list_del(&mchan->chan.device_node);

origial code have not list_del(), is it fix other problem?

Frank
> +	}
>  }
>
>  static unsigned int nr_desc_prm;
> @@ -155,6 +161,13 @@ static void hidma_process_completed(struct hidma_chan *mchan)
>  	}
>  }
>
> +static void hidma_chan_bh(struct dma_chan *chan)
> +{
> +	struct hidma_chan *mchan = to_hidma_chan(chan);
> +
> +	hidma_process_completed(mchan);
> +}
> +
>  /*
>   * Called once for each submitted descriptor.
>   * PM is locked once for each descriptor that is currently
> @@ -181,7 +194,7 @@ static void hidma_callback(void *data)
>  	}
>  	spin_unlock_irqrestore(&mchan->lock, irqflags);
>
> -	hidma_process_completed(mchan);
> +	dmaengine_schedule_bh(&mchan->chan);
>
>  	if (queued) {
>  		pm_runtime_mark_last_busy(dmadev->ddev.dev);
> @@ -203,6 +216,7 @@ static int hidma_chan_init(struct hidma_dev *dmadev, u32 dma_sig)
>  	mchan->dmadev = dmadev;
>  	mchan->chan.device = ddev;
>  	dma_cookie_init(&mchan->chan);
> +	dmaengine_init_bh(&mchan->chan, hidma_chan_bh);
>
>  	INIT_LIST_HEAD(&mchan->free);
>  	INIT_LIST_HEAD(&mchan->prepared);
> --
> 2.43.0
>