Re: [PATCH v7 06/24] dmaengine: ste_dma40: Check runtime PM in IRQ

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] dmaengine: ste_dma40: IRQ storm due to unhandled interrupt during RPM_RESUMING
--

commit 5c375e7c3c832d3f8400ed368962408e5da22738
Author: Linus Walleij <linusw@kernel.org>

dmaengine: ste_dma40: Check runtime PM in IRQ

d40_handle_interrupt() reads DMA40 interrupt registers unconditionally. A
spurious interrupt can arrive while the device is runtime suspended, after
dma40_runtime_suspend() has disabled the GCC clock. Avoid touching the
registers unless the device is runtime active by taking a conditional
runtime PM reference.

> diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
> index 1dcfeabb3f363..5e9b6342c5a9e 100644
> --- a/drivers/dma/ste_dma40.c
> +++ b/drivers/dma/ste_dma40.c
> @@ -1807,6 +1807,11 @@ static irqreturn_t d40_handle_interrupt(int irq, void *data)
>  	u32 *regs = base->regs_interrupt;
>  	struct d40_interrupt_lookup *il = base->gen_dmac.il;
>  	u32 il_size = base->gen_dmac.il_size;
> +	int ret;
> +
> +	ret = pm_runtime_get_if_active(base->dev);
> +	if (IS_ENABLED(CONFIG_PM) && ret <= 0)
> +		return IRQ_NONE;

[Severity: High]
Does returning IRQ_NONE here cause an IRQ storm during device resume?

In dma40_runtime_resume(), the hardware clocks are enabled which immediately
asserts any pending interrupts. However, the PM core's status is still
RPM_RESUMING, causing pm_runtime_get_if_active() to return 0.

Because the interrupt handler skips acknowledging the hardware interrupt and
returns IRQ_NONE, the level-triggered interrupt remains asserted.

A similar situation can happen during system suspend when
pm_runtime_force_suspend() disables runtime PM (disable_depth > 0), causing
pm_runtime_get_if_active() to return -EINVAL.

Will this cause the kernel to eventually disable the interrupt line
("nobody cared") and permanently break the DMA controller?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260927-dma40-fixes-v7-0-89f595e8851d@kernel.org?part=6