linux-kernel - Re: [PATCH 4/9] pinctrl: meson: allow gpio to request irq

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Date:   Thu, 20 Oct 2016 21:21:04 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Jerome Brunet <jbrunet@...libre.com>
Cc:     Carlo Caione <carlo@...one.org>,
        Kevin Hilman <khilman@...libre.com>,
        "open list:ARM/Amlogic Meson..." <linux-amlogic@...ts.infradead.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        Marc Zyngier <marc.zyngier@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH 4/9] pinctrl: meson: allow gpio to request irq

On Wed, Oct 19, 2016 at 12:08 PM, Jerome Brunet <jbrunet@...libre.com> wrote:

> Add the ability for gpio to request irq from the gpio interrupt controller
> if present. We have to specificaly that the parent interrupt controller is
> the gpio interrupt controller because gpio on meson SoCs can't generate
> interrupt directly on the GIC.
>
> Signed-off-by: Jerome Brunet <jbrunet@...libre.com>
(...)
> +       select IRQ_DOMAIN
>         select OF_GPIO
> +       select OF_IRQ
(...)
> +static int meson_gpio_to_hwirq(struct meson_bank *bank, unsigned int offset)
> +{
> +       unsigned int hwirq;
> +
> +       if (bank->irq_first < 0)
> +               /* this bank cannot generate irqs */
> +               return -1;
> +
> +       hwirq = offset - bank->first + bank->irq_first;
> +
> +       if (hwirq > bank->irq_last)
> +               /* this pin cannot generate irqs */
> +               return -1;
> +
> +       return hwirq;
> +}

This is reimplementing irqdomain.

> +static int meson_gpio_to_irq(struct gpio_chip *chip, unsigned int offset)
> +{
(...)
> +       hwirq = meson_gpio_to_hwirq(bank, offset);
> +       if (hwirq < 0) {
> +               dev_dbg(pc->dev, "no interrupt for pin %u\n", offset);
> +               return 0;
> +       }

Isn't this usecase (also as described in the cover letter) a textbook
example of when you should be using hierarchical irqdomain?

Please check with Marc et al on hierarchical irqdomains.

Yours,
Linus Walleij