Re: [PATCH v4 19/24] dmaengine: dw-edma: Drain LL entries for STOP and PAUSE

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Infinite loop in dw_edma_wait_termination() leading to hung tasks if hardware stalls or is removed.
--

--- Patch [19]: [PATCH v4 19/24] dmaengine: dw-edma: Drain LL entries for STOP and PAUSE ---
commit 7c90dd7ea15ac01e52b8a14ed044dee1a6a2bfde
Author: Koichiro Den <den@valinux.co.jp>
Subject: dmaengine: dw-edma: Drain LL entries for STOP and PAUSE

This commit changes the channel termination process to wait for the
hardware to consume all published LL entries when a STOP or PAUSE is
requested, rather than discarding the ring state immediately.

> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index b0e3f67d3942f..977392689205f 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c

[ ... ]

> @@ -1590,18 +1638,21 @@ static void dw_edma_wait_termination(struct dma_chan *dchan)
>  	 * A STOP may be deferred to a later interrupt while the channel is still
>  	 * running. Wait until that handler completes the termination.
>  	 */
> -	while (time_before(jiffies, timeout)) {
> +	for (;;) {
>  		scoped_guard(spinlock_irqsave, &chan->vc.lock)
>  			stopping = chan->request == EDMA_REQ_STOP;
>  
>  		if (!stopping)
>  			return;
>  
> +		if (time_after_eq(jiffies, timeout)) {
> +			dev_warn(chan->dw->chip->dev,
> +				 "timeout waiting for channel termination; still waiting\n");
> +			timeout = jiffies + msecs_to_jiffies(5000);
> +		}
> +
>  		fsleep(1000);
>  	}

[Severity: High]
Does this change introduce a potential infinite loop? By removing the absolute
timeout and converting this to an unbounded for (;;) loop, the function will
hang forever if the hardware stalls, drops an interrupt, or is
surprise-removed.

If chan->request never transitions away from EDMA_REQ_STOP (for example, if
dw->teardown is set and no further interrupts arrive),
dmaengine_terminate_sync() will block indefinitely. This could prevent driver
unbind, system suspend, or process exit.

Is there a fallback mechanism to eventually break out of this loop if the
hardware never recovers?

> -
> -	dev_warn(chan->dw->chip->dev,
> -		 "timeout waiting for channel termination\n");
>  }
>  
>  static void dw_edma_device_synchronize(struct dma_chan *dchan)

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260729143036.3087722-1-den@valinux.co.jp?part=19