Date:   Fri, 13 May 2022 08:53:38 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Lad, Prabhakar" <prabhakar.csengg@...il.com>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Phil Edworthy <phil.edworthy@...esas.com>,
        Biju Das <biju.das.jz@...renesas.com>
Subject: Re: [PATCH v3 5/5] pinctrl: renesas: pinctrl-rzg2l: Add IRQ domain to
 handle GPIO interrupt

Hi Prabhakar,

On Thu, May 12, 2022 at 7:36 PM Lad, Prabhakar
<prabhakar.csengg@...il.com> wrote:
> On Thu, May 12, 2022 at 8:39 AM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > On Wed, May 11, 2022 at 8:32 PM Lad Prabhakar
> > <prabhakar.mahadev-lad.rj@...renesas.com> wrote:
> > > Add IRQ domian to RZ/G2L pinctrl driver to handle GPIO interrupt.
> > > GPIO0-GPIO122 pins can be used as IRQ lines but only 32 pins can be
> > > used as IRQ lines at given time. Selection of pins as IRQ lines
> > > is handled by IA55 (which is the IRQC block) which sits in between the
> > > GPIO and GIC.
> > >
> > > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >
> > Thanks for your patch!
> >
> > > --- a/drivers/pinctrl/renesas/pinctrl-rzg2l.c
> > > +++ b/drivers/pinctrl/renesas/pinctrl-rzg2l.c
> >
> > >  static int rzg2l_gpio_register(struct rzg2l_pinctrl *pctrl)
> > >  {
> > >         struct device_node *np = pctrl->dev->of_node;
> > >         struct gpio_chip *chip = &pctrl->gpio_chip;
> > >         const char *name = dev_name(pctrl->dev);
> > > +       struct irq_domain *parent_domain;
> > >         struct of_phandle_args of_args;
> > > +       struct device_node *parent_np;
> > > +       struct gpio_irq_chip *girq;
> > >         int ret;
> > >
> > > +       parent_np = of_irq_find_parent(np);
> > > +       if (!parent_np)
> > > +               return -ENXIO;
> > > +
> > > +       parent_domain = irq_find_host(parent_np);
> > > +       of_node_put(parent_np);
> > > +       if (!parent_domain)
> > > +               return -EPROBE_DEFER;
> > > +
> > >         ret = of_parse_phandle_with_fixed_args(np, "gpio-ranges", 3, 0, &of_args);
> > >         if (ret) {
> > >                 dev_err(pctrl->dev, "Unable to parse gpio-ranges\n");
> > > @@ -1138,6 +1330,15 @@ static int rzg2l_gpio_register(struct rzg2l_pinctrl *pctrl)
> > >         chip->base = -1;
> > >         chip->ngpio = of_args.args[2];
> > >
> > > +       girq = &chip->irq;
> > > +       girq->chip = &rzg2l_gpio_irqchip;
> > > +       girq->fwnode = of_node_to_fwnode(np);
> > > +       girq->parent_domain = parent_domain;
> > > +       girq->child_to_parent_hwirq = rzg2l_gpio_child_to_parent_hwirq;
> > > +       girq->populate_parent_alloc_arg = rzg2l_gpio_populate_parent_fwspec;
> > > +       girq->child_irq_domain_ops.free = rzg2l_gpio_irq_domain_free;
> > > +       girq->ngirq = RZG2L_TINT_MAX_INTERRUPT;
> > > +
> >
> > I think you need to provide a .init_valid_mask() callback, as
> > gpiochip_irqchip_remove() relies on that for destroying interrupts.
> Are you suggesting  the callback to avoid looping through all the GPIO pins?

gpiochip_irqchip_remove() does:

        /* Remove all IRQ mappings and delete the domain */
        if (gc->irq.domain) {
                unsigned int irq;

                for (offset = 0; offset < gc->ngpio; offset++) {
                       if (!gpiochip_irqchip_irq_valid(gc, offset))
                                continue;

                        irq = irq_find_mapping(gc->irq.domain, offset);
                        irq_dispose_mapping(irq);
                }

                irq_domain_remove(gc->irq.domain);

        }

The main thing is not about avoiding to loop through all GPIO pins,
but to avoid irq_{find,dispose}_mapping() doing the wrong thing.
The loop is over all GPIO offsets, while not all of them are mapped
to valid interrupts. Does the above work correctly?

> > However, the mask will need to be dynamic, as GPIO interrupts can be
> > mapped and unmapped to one of the 32 available interrupts dynamically,
> > right?
> Yep that's correct.
>
> > I'm not sure if that can be done easily: if gpiochip_irqchip_irq_valid()
> > is ever called too early, before the mapping is done, it would fail.
> >
> The mask initialization is a one time process and that is during
> adding the GPIO chip. At this stage we won't be knowing what will be
> the valid GPIO pins used as interrupts. Maybe the core needs to
> implement a callback which lands in the GPIO controller driver to tell
> if the gpio irq line is valid. This way we can handle dynamic
> interrupts.

Upon closer look, I think the mask is a red herring, and we don't
need it.
But we do need to handle the (possible) mismatch between GPIO
offset (index) and IRQ offset in the above code.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

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