Re: [PATCH v17 03/14] dmaengine: qcom: bam_dma: convert tasklet to a BH workqueue

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] PM usage counter leak on failure in bam_start_dma() and bam_dma_irq()
--

commit 16a499b407c35e00637c627257ad62de2a108b14
Author: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

dmaengine: qcom: bam_dma: convert tasklet to a BH workqueue

This commit replaces the legacy tasklet implementation in the BAM DMA
driver with a high-priority BH workqueue.

> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index cea44833201d6..e2f16efcdb55f 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
[ ... ]
> @@ -893,9 +894,9 @@ static irqreturn_t bam_dma_irq(int irq, void *data)
>  
>  	srcs |= process_channel_irqs(bdev);
>  
> -	/* kick off tasklet to start next dma transfer */
> +	/* kick off the work queue to start next dma transfer */
>  	if (srcs & P_IRQ)
> -		tasklet_schedule(&bdev->task);
> +		queue_work(system_bh_highpri_wq, &bdev->work);
>  
>  	ret = pm_runtime_get_sync(bdev->dev);
>  	if (ret < 0)
>  		return IRQ_NONE;

Does this code leak the PM usage counter if pm_runtime_get_sync() returns
a negative value?

While this wasn't introduced by this patch, pm_runtime_get_sync()
unconditionally increments the usage counter before checking the state.
Returning IRQ_NONE here without dropping the counter permanently prevents
the device from entering runtime suspend again.

Could this be updated to use pm_runtime_resume_and_get() instead, which
automatically drops the usage counter on failure?

[ ... ]
> @@ -1111,14 +1112,13 @@ static void dma_tasklet(struct tasklet_struct *t)
>  		if (!list_empty(&bchan->vc.desc_issued) && !IS_BUSY(bchan))
>  			bam_start_dma(bchan);

A similar pattern is present in bam_start_dma(), which is executed by this
newly added work queue callback. It calls pm_runtime_get_sync() and returns
early on failure without dropping the usage counter.

>  	}
> -
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260519-qcom-qce-cmd-descr-v17-0-53a595414b79@oss.qualcomm.com?part=3