Re: [PATCH v3 09/10] mailbox: imx: Don't force-thread the primary handler

[sashiko-bot@kernel.org]

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

Pre-existing issues:
- [High] The return value of `pm_runtime_get_sync()` is ignored in `imx_mu_startup()`, risking unclocked register accesses and PM reference leaks.
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commit 14f99570339a0f5e4729690bf8d39e0fdeb47ac3
Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

mailbox: imx: Don't force-thread the primary handler

This commit optimizes the i.MX mailbox driver by converting the
xcr_lock to a raw_spinlock_t and marking the primary interrupt handler
with IRQF_NO_THREAD. This prevents the primary handler from being
force-threaded, allowing it to run in hardirq context even on PREEMPT_RT.

> diff --git a/drivers/mailbox/imx-mailbox.c b/drivers/mailbox/imx-mailbox.c
> --- a/drivers/mailbox/imx-mailbox.c
> +++ b/drivers/mailbox/imx-mailbox.c

[ ... ]

> @@ -640,7 +635,7 @@ static int imx_mu_startup(struct mbox_chan *chan)
>  {
>  	struct imx_mu_priv *priv = to_imx_mu_priv(chan->mbox);
>  	struct imx_mu_con_priv *cp = chan->con_priv;
> -	unsigned long irq_flag = 0;
> +	unsigned long irq_flag = IRQF_NO_THREAD;
>  	int ret;
>  
>  	pm_runtime_get_sync(priv->dev);

[Severity: High]
This isn't a bug introduced by this patch, but should the return value of
pm_runtime_get_sync() be checked here?

If the device fails to resume (e.g., the PM domain fails to power on),
pm_runtime_get_sync() returns a negative error code but leaves the PM
usage counter incremented. Because the return value goes unchecked, the
driver might incorrectly assume the hardware is ready and proceed to call
hardware access functions like imx_mu_xcr_rmw() during startup.

Accessing unclocked or unpowered registers on i.MX devices can cause an
asynchronous external abort (bus fault), leading to a system crash. Could
this be updated to use pm_runtime_resume_and_get() instead, allowing the
driver to safely abort the startup on failure?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260617-imx_mbox_rproc-v3-0-77948112defc@linutronix.de?part=9