linux-kernel - Re: [PATCH 1/1] pinctrl: st: add irq_request

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Date:   Tue, 14 Mar 2017 15:05:27 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Patrice CHOTARD <patrice.chotard@...com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Peter Griffin <peter.griffin@...aro.org>,
        Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH 1/1] pinctrl: st: add irq_request_resources callback

On Mon, Feb 27, 2017 at 2:49 PM,  <patrice.chotard@...com> wrote:

> From: Patrice Chotard <patrice.chotard@...com>
>
> When using GPIO as IRQ source, the GPIO must be configured
> in INPUT. The callback dedicated for this was missing in
> pinctrl-st driver.
>
> This fix the following kernel error when trying to lock a gpio
> as IRQ:
>
> [    7.521095] gpio gpiochip7: (PIO11): gpiochip_lock_as_irq: tried to flag a GPIO set as output for IRQ
> [    7.526018] gpio gpiochip7: (PIO11): unable to lock HW IRQ 6 for IRQ
> [    7.529405] genirq: Failed to request resources for 0-0053 (irq 81) on irqchip GPIO
>
> Signed-off-by: Patrice Chotard <patrice.chotard@...com>

I see what problem you are trying to solve.

> +static int st_gpio_irq_request_resources(struct irq_data *d)
> +{
> +       struct gpio_chip *gc = irq_data_get_irq_chip_data(d);
> +       int pin = d->hwirq;
> +
> +       return st_gpio_direction_input(gc, pin);
> +}
(...)
> +       .irq_request_resources  = st_gpio_irq_request_resources,

But this is just hiding the problem I'm afraid.

Now thay you override .irq_request_resources()
gpiochip_irq_reqres() will not be called, so then you have
to lock the irq in the driver, with something like:

ret = gpiochip_lock_as_irq(&chip->gc, d->hwirq);
        if (ret)
                goto out;

You also have to implement the .irq_release_resources()
callback and unlock the IRQ there.

Yours,
Linus Walleij