Re: [PATCH] gpiolib-acpi: Only defer request_irq for GpioInt ACPI event handlers

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, Nov 26, 2018 at 11:42:31AM +0100, Hans de Goede wrote:
> Commit 78d3a92edbfb ("gpiolib-acpi: Register GpioInt ACPI event handlers
> from a late_initcall") deferred the entire acpi_gpiochip_request_interrupt
> call for each event resource.
> 
> This means it also delays the gpiochip_request_own_desc(..., "ACPI:Event")
> call. This is a problem if some AML code reads the GPIO pin before we
> run the deferred acpi_gpiochip_request_interrupt, because in that case
> acpi_gpio_adr_space_handler() will already have called
> gpiochip_request_own_desc(..., "ACPI:OpRegion") causing the call from
> acpi_gpiochip_request_interrupt to fail with -EBUSY and we will fail to
> register an event handler.
> 
> acpi_gpio_adr_space_handler is prepared for acpi_gpiochip_request_interrupt
> already having claimed the pin, but the other way around does not work.
> 
> One example of a problem this causes, is the event handler for the OTG
> ID pin on a Prowise PT301 tablet not registering, keeping the port stuck
> in whatever mode it was in during boot and e.g. only allowing charging
> after a reboot.
> 
> This commit fixes this by only deferring the request_irq call and the
> initial run of edge-triggered IRQs instead of deferring all of
> acpi_gpiochip_request_interrupt.

Thanks for a patch with such nice description.
I have couple of nitpicks and one question below.


>   * For gpiochips which call acpi_gpiochip_request_interrupts() before late_init
> - * (so builtin drivers) we register the ACPI GpioInt event handlers from a
> + * (so builtin drivers) we register the ACPI GpioInt irq-handlers from a

I would rather spell "IRQ handlers"

>   * late_initcall_sync handler, so that other builtin drivers can register their
>   * OpRegions before the event handlers can run.  This list contains gpiochips
> - * for which the acpi_gpiochip_request_interrupts() has been deferred.
> + * for which the acpi_gpiochip_request_irqs() call has been deferred.

>  	mutex_unlock(&acpi_gpio_deferred_req_irqs_lock);
>  
> -	if (defer)
> -		return;
> -
> -	acpi_walk_resources(handle, "_AEI",
> -			    acpi_gpiochip_request_interrupt, acpi_gpio);
> +	if (!defer)
> +		acpi_gpiochip_request_irqs(acpi_gpio);

Can we leave above condition and put here just

	acpi_gpiochip_request_irqs(acpi_gpio);

?

>  	list_for_each_entry_safe_reverse(event, ep, &acpi_gpio->events, node) {
>  		struct gpio_desc *desc;
>  
> +		if (event->irq_requested) {
> +			if (event->irq_is_wake)
> +				disable_irq_wake(event->irq);
> +
> +			free_irq(event->irq, event);
> +		}
>  


>  		desc = event->desc;
>  		if (WARN_ON(IS_ERR(desc)))

I don't remember if I asked already about possible memory leak here.
Am I reading code right?

>  			continue;

Reading more code, I'm even not sure if this condition could ever happen.

-- 
With Best Regards,
Andy Shevchenko