linux-kernel - Re: [PATCH v4 2/2] gpio: sch: Hook into ACPI SCI handler to catch GPIO edge events

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Date:   Tue, 16 Mar 2021 19:05:48 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Jan Kiszka <jan.kiszka@...mens.com>, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     Andy Shevchenko <andy@...nel.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>
Subject: Re: [PATCH v4 2/2] gpio: sch: Hook into ACPI SCI handler to catch
 GPIO edge events

On Tue, Mar 16, 2021 at 06:26:13PM +0200, Andy Shevchenko wrote:
> From: Jan Kiszka <jan.kiszka@...mens.com>
> 
> Neither the ACPI description on the Quark platform provides the required
> information is to do establish generic handling nor hardware capable of
> doing it. According to the datasheet the hardware can generate SCI events.
> Therefore, we need to hook from the driver directly into SCI handler of
> the ACPI subsystem in order to catch and report GPIO-related events.

> Validated on the Quark-based IOT2000 platform.

This depends on the test by Jan or somebody with the same hardware available.

> +static u32 sch_gpio_sci_handler(void *context)
> +{
> +	struct sch_gpio *sch = context;
> +	struct gpio_chip *gc = &sch->chip;
> +	unsigned long core_status, resume_status;
> +	unsigned long pending;
> +	int offset;

> +	core_status = inl(sch->iobase + GTS + 0x00);
> +	resume_status = inl(sch->iobase + GTS + 0x20);
> +
> +	pending = (resume_status << sch->resume_base) | core_status;
> +
> +	for_each_set_bit(offset, &pending, sch->chip.ngpio)
> +		generic_handle_irq(irq_find_mapping(gc->irq.domain, offset));
> +
> +	outl(core_status, sch->iobase + GTS + 0x00);
> +	outl(resume_status, sch->iobase + GTS + 0x20);

I guess this still needs to be protected by spin_lock.

> +	return pending ? ACPI_INTERRUPT_HANDLED : ACPI_INTERRUPT_NOT_HANDLED;
> +}

...

Also I am in doubt that we need to instantiate an IRQ chip if the ACPI SCI
handler registration fails. But I don't know what is better approach here, to
NULL the pointer, or try to register handler before we will have an IRQ chip in
place. Any recommendations?

-- 
With Best Regards,
Andy Shevchenko