Re: [PATCH 12/26] dmaengine: sh-rcar-dmac: Remove redundant dev_err()/dev_err_probe()

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] System crash due to unclocked register access on spurious interrupt
--

--- Patch [12]: [PATCH 12/26] dmaengine: sh-rcar-dmac: Remove redundant dev_err()/dev_err_probe() ---
commit 910ca9859b95c7ea2133b72448deeefa62bebf2b
Author: Pan Chuang <panchuang@vivo.com>

dmaengine: sh-rcar-dmac: Remove redundant dev_err()/dev_err_probe()

This commit removes driver-specific error logging when requesting the
channel interrupt. The logging is removed because
devm_request_threaded_irq() now automatically logs detailed error messages
on failure.

> diff --git a/drivers/dma/sh/rcar-dmac.c b/drivers/dma/sh/rcar-dmac.c
> index 44eab2d21d54f..4cd7f0189bc7b 100644
> --- a/drivers/dma/sh/rcar-dmac.c
> +++ b/drivers/dma/sh/rcar-dmac.c
> @@ -1793,11 +1793,8 @@ static int rcar_dmac_chan_probe(struct rcar_dmac *dmac,
>  					rcar_dmac_isr_channel,
>  					rcar_dmac_isr_channel_thread, 0,
>  					irqname, rchan);

[Severity: High]
This is a pre-existing issue, but is it safe to leave the interrupt active
when the device enters runtime suspend?

Since the IRQ is managed by devm_request_threaded_irq(), it remains
unmasked even when the power domain gates the clock (for example, after
rcar_dmac_probe() calls pm_runtime_put()).

If a spurious interrupt fires while the clock is gated, the hardirq
handler unconditionally accesses a device register:

rcar_dmac_isr_channel() {
        ...
        chcr = rcar_dmac_chan_read(chan, RCAR_DMACHCR);
        ...
}

Could this unclocked register read cause a synchronous external abort and
subsequent kernel panic?

A similar window appears to exist in rcar_dmac_remove(). It calls
pm_runtime_disable(), which leaves the clock disabled if the device was
already suspended, before devres unregisters the IRQ. Can a spurious
interrupt during this teardown phase also trigger the same panic?

> -	if (ret) {
> -		dev_err(dmac->dev, "failed to request IRQ %u (%d)\n",
> -			rchan->irq, ret);
> +	if (ret)
>  		return ret;
> -	}
>  
>  	return 0;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260709135846.97972-1-panchuang@vivo.com?part=12