Re: [PATCH] gpio: ml-ioh: use raw_spinlock_t for the register lock

On Fri, Jul 31, 2026 at 5:30=E2=80=AFAM Junjie Cao <[email protected]> w=
rote:

> ioh_irq_type() is registered as the irq_chip .irq_set_type callback and
> takes chip->spinlock with spin_lock_irqsave().  This callback is reached
> from __setup_irq() -> __irq_set_trigger() -> chip->irq_set_type() while
> the caller holds desc->lock, a raw_spinlock_t, with hardirqs disabled.
> That context is not sleepable, but on PREEMPT_RT a regular spinlock_t is
> an rtmutex-backed sleeping lock, so acquiring it there is invalid.
> ioh_irq_enable() and ioh_irq_disable() take the same lock from the
> .irq_enable/.irq_disable callbacks, which are likewise invoked with
> desc->lock held.
>
> Convert the register lock to raw_spinlock_t.  The same lock also
> serializes the GPIO direction/value callbacks and the suspend/resume
> register save/restore, and those critical sections only perform short
> sequences of MMIO register accesses (ioread32()/iowrite32()); the
> .irq_set_type callback additionally emits a dev_warn() on an unsupported
> type.  None of these are sleepable operations, so keeping this register
> lock non-sleeping is appropriate for the irqchip callbacks and does not
> change the GPIO-side locking contract.
>
> This is the same fix as commit a02b8950d619 ("gpio: pch: use
> raw_spinlock_t for the register lock"); this driver shares the same
> structure as gpio-pch.
>
> Fixes: 54be566317b6 ("gpio-ml-ioh: Support interrupt function")
> Cc: [email protected]
> Signed-off-by: Junjie Cao <[email protected]>

Reviewed-by: Linus Walleij <[email protected]>

If you have time, look into the issue reported by sashiko about suspend/res=
ume
ignoring the spinlock.

Thanks!
Linus Walleij