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

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Date:   Fri, 21 Oct 2016 11:06:38 +0200
From:   Jerome Brunet <jbrunet@...libre.com>
To:     Linus Walleij <linus.walleij@...aro.org>
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 Thu, 2016-10-20 at 21:21 +0200, Linus Walleij wrote:
> 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.

Linus,
Do you mean I should create a new hierarchical irqdomains in each of
the two pinctrl instances we have in these SoC, these domains being
stacked on the one I just added for controller in irqchip ?

I did not understand this is what you meant when I asked you the
question at ELCE.

> 
> Yours,
> Linus Walleij