Re: [PATCH 16/23] gpio: nomadik: support shared GPIO IRQs

Théo Lebrun
2024-02-19T15:54:57Z

Hello,

On Mon Feb 19, 2024 at 4:48 PM CET, Bartosz Golaszewski wrote:
> On Wed, Feb 14, 2024 at 5:24 PM Théo Lebrun <theo.lebrun@bootlin.com> wrote:
> >
> > Support a single IRQs used by multiple GPIO banks. Change the IRQ
> > handler type from a chained handler (as used by gpiolib
> > for ->parent_handler) to a threaded IRQ.
> >
> > Use a fake raw spinlock to ensure generic_handle_irq() is called in a
> > no-irq context. See Documentation/driver-api/gpio/driver.rst, "CHAINED
> > CASCADED GPIO IRQCHIPS" for additional information.
> >
>
> Any reason for not using preempt_disable()?

I did what the doc recommended:

> The generic_handle_irq() is expected to be called with IRQ disabled,
> so the IRQ core will complain if it is called from an IRQ handler which is
> forced to a thread. The "fake?" raw lock can be used to work around this
> problem::
>
> raw_spinlock_t wa_lock;
> static irqreturn_t omap_gpio_irq_handler(int irq, void *gpiobank)
> unsigned long wa_lock_flags;
> raw_spin_lock_irqsave(&bank->wa_lock, wa_lock_flags);
> generic_handle_irq(irq_find_mapping(bank->chip.irq.domain, bit));
> raw_spin_unlock_irqrestore(&bank->wa_lock, wa_lock_flags);

If you confirm I should be using preempt_disable() that's what I'll do
in the next revision. I could even throw in a documentation patch if
the advice is outdated.

Thanks Bartosz,

--
Théo Lebrun, Bootlin
Embedded Linux and Kernel engineering