linux-kernel - Re: [PATCH v3 1/2] gpio: sch: Add edge event support

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Message-ID: <CACRpkdbE_gkm4n3_V3_D0mKL4dF1pYC1ORbg07YSk24TpYrjTw@mail.gmail.com>
Date:   Thu, 28 Nov 2019 10:33:40 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Jan Kiszka <jan.kiszka@...mens.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>
Subject: Re: [PATCH v3 1/2] gpio: sch: Add edge event support

Hi Jan,

thanks for your patch!

On Wed, Nov 20, 2019 at 8:20 PM Jan Kiszka <jan.kiszka@...mens.com> wrote:

> From: Jan Kiszka <jan.kiszka@...mens.com>
>
> Add the required infrastructure consisting of an irq_chip_generic with
> its irq_chip_type callbacks to enable and report edge events of the pins
> to the gpio core. The actual hook-up of the event interrupt will happen
> separately.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@...mens.com>

Please resend after the merge window, some comments:

First I'm pretty sure this driver can select GPIOLIB_IRQCHIP
and use infrastructure from the core to handle interrupts.

The fact that you register your own irq handler does not
stop that. See for example the solution in
drivers/gpio/gpio-mt7621.c
where we set the ->parent_handler to NULL to let
the driver handle the IRQs itself.

I will try to make this more explicit in the API as we work
with this.

>  struct sch_gpio {
>         struct gpio_chip chip;
>         spinlock_t lock;
>         unsigned short iobase;
>         unsigned short resume_base;
> +       int irq_base;

Why are you keeping this around in the state?
Why not just a local variable?

> +static int sch_gpio_to_irq(struct gpio_chip *gpio, unsigned int offset)
> +{
> +       struct sch_gpio *sch = gpiochip_get_data(gpio);
> +       return sch->irq_base + offset;
> +}
(...)
> +       .to_irq                 = sch_gpio_to_irq,
(...)
> +       irq_base = devm_irq_alloc_descs(&pdev->dev, -1, 0, sch->chip.ngpio,
> +                                       NUMA_NO_NODE);
> +       if (irq_base < 0)
> +               return irq_base;
> +       sch->irq_base = irq_base;
> +
> +       gc = devm_irq_alloc_generic_chip(&pdev->dev, "sch_gpio", 1, irq_base,
> +                                        NULL, handle_simple_irq);
> +       if (!gc)
> +               return -ENOMEM;
(...)
> +       ret = devm_irq_setup_generic_chip(&pdev->dev, gc,
> +                                         IRQ_MSK(sch->chip.ngpio),
> +                                         0, IRQ_NOREQUEST | IRQ_NOPROBE, 0);
> +       if (ret)
> +               return ret;

So I think you can avoid this complexity by jus doing what
gpio-mt7621.c is doing,
use devm_request_irq(), populate girq = &gc->irq; before
registering the gpio_chip pass a handle_simple_irq
and reuse core gpio irqchip infrastructure.

But I don't know everything so let's test and see!

Yours,
Linus Walleij