Re: [PATCH v6 08/23] dmaengine: ste_dma40: Return IRQ_NONE when no interrupt is pending

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

On Thu, Sep 24, 2026 at 10:35:20AM +0200, Linus Walleij wrote:
> d40_handle_interrupt() returns IRQ_HANDLED even when no terminal-count or
> error status bit is pending.
>
> IRQ_NONE is not only used to identify a device on a shared interrupt.
> The generic IRQ core also counts it as unhandled for spurious IRQ
> detection. DMA40 does not request this IRQ with IRQF_SHARED, so interrupt
> sharing is not the purpose of this change.
>
> If the line remains asserted without matching DMA40 status, returning
> IRQ_HANDLED hides the stuck interrupt and can leave the CPU servicing it
> indefinitely. Track whether any DMA40 status is pending and return IRQ_NONE
> when none is present, allowing the generic IRQ core to diagnose and
> eventually disable the faulty line.
>
> DMA40 channels can be owned by other SoC cores. Their status means that
> the interrupt is real, but Linux must not acknowledge it. Treat foreign
> status as handled and leave its acknowledgment to the owning core, while
> acknowledging and dispatching only registered Linux channels.
>
> Fixes: 8d318a50b3d7 ("DMAENGINE: Support for ST-Ericssons DMA40 block v3")
> Assisted-by: LLM
> Signed-off-by: Linus Walleij <linusw@kernel.org>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

>  drivers/dma/ste_dma40.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
> index 712719f0c4cf..271f653a15c4 100644
> --- a/drivers/dma/ste_dma40.c
> +++ b/drivers/dma/ste_dma40.c
> @@ -1819,6 +1819,7 @@ static void dma_tasklet(struct tasklet_struct *t)
>
>  static irqreturn_t d40_handle_interrupt(int irq, void *data)
>  {
> +	irqreturn_t handled = IRQ_NONE;
>  	int i;
>  	u32 idx;
>  	u32 row;
> @@ -1852,6 +1853,12 @@ static irqreturn_t d40_handle_interrupt(int irq, void *data)
>  		row = chan / BITS_PER_LONG;
>  		idx = chan & (BITS_PER_LONG - 1);
>
> +		/*
> +		 * Status for a channel owned by another core still explains
> +		 * the interrupt, but only ACK Linux-owned channels below.
> +		 */
> +		handled = IRQ_HANDLED;
> +
>  		if (il[row].offset == D40_PHY_CHAN)
>  			d40c = base->lookup_phy_chans[idx];
>  		else
> @@ -1884,7 +1891,7 @@ static irqreturn_t d40_handle_interrupt(int irq, void *data)
>  	if (ret > 0)
>  		pm_runtime_put_autosuspend(base->dev);
>
> -	return IRQ_HANDLED;
> +	return handled;
>  }
>
>  static int d40_validate_conf(struct d40_chan *d40c,
>
> --
> 2.55.0
>