linux-kernel - Re: [PATCH v3 1/2] gpio: Add support for hierarchical IRQ domains

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Message-ID: <CACRpkdb5vB6OwcAxtjsKLzHt9V27juEOEEDqqQczKT-3r+7X-g@mail.gmail.com>
Date:   Sun, 2 Jun 2019 15:46:00 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Lina Iyer <ilina@...eaurora.org>,
        Jon Hunter <jonathanh@...dia.com>,
        Sowjanya Komatineni <skomatineni@...dia.com>,
        Bitan Biswas <bbiswas@...dia.com>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        linux-tegra@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/2] gpio: Add support for hierarchical IRQ domains

On Wed, May 29, 2019 at 4:53 PM Thierry Reding <thierry.reding@...il.com> wrote:

> From: Thierry Reding <treding@...dia.com>
>
> Hierarchical IRQ domains can be used to stack different IRQ controllers
> on top of each other. One specific use-case where this can be useful is
> if a power management controller has top-level controls for wakeup
> interrupts. In such cases, the power management controller can be a
> parent to other interrupt controllers and program additional registers
> when an IRQ has its wake capability enabled or disabled.
>
> Signed-off-by: Thierry Reding <treding@...dia.com>
> ---
> Changes in v3:
> - use irq_create_fwspec_mapping() instead of irq_domain_alloc_irqs()
> - add missing kerneldoc for new parent_domain field
> - keep IRQ_DOMAIN dependency for clarity
>
> Changes in v2:
> - select IRQ_DOMAIN_HIERARCHY to avoid build failure
> - move more code into the gpiolib core

This is looking really good!

>  config GPIOLIB_IRQCHIP
>         select IRQ_DOMAIN
> +       select IRQ_DOMAIN_HIERARCHY
>         bool

Hm OK I guess. It would be ugly to ifdef all hierarchy
code in gpiolib.

>  static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
>  {
> +       struct irq_domain *domain = chip->irq.domain;
> +
>         if (!gpiochip_irqchip_irq_valid(chip, offset))
>                 return -ENXIO;
>
> +       if (irq_domain_is_hierarchy(domain)) {
> +               struct irq_fwspec spec;
> +
> +               spec.fwnode = domain->fwnode;
> +               spec.param_count = 2;
> +               spec.param[0] = offset;
> +               spec.param[1] = IRQ_TYPE_NONE;
> +
> +               return irq_create_fwspec_mapping(&spec);
> +       }
> +
>         return irq_create_mapping(chip->irq.domain, offset);

This is looking really good!

> +       /*
> +        * Allow GPIO chips to override the ->to_irq() if they really need to.
> +        * This should only be very rarely needed, the majority should be fine
> +        * with gpiochip_to_irq().
> +        */
> +       if (!gpiochip->to_irq)
> +               gpiochip->to_irq = gpiochip_to_irq;

Please drop this. The default .to_irq() should be good for everyone.
Also patch 2/2 now contains a identical copy of the gpiolib
.to_irq() which I suspect you indended to drop, actually.

Other than that I'm ready to merge the v3 of this!

Yours,
Linus Walleij