linux-kernel - Re: [PATCH v4 6/6] gpio: uniphier: add UniPhier GPIO controller driver

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Message-ID: <CACRpkdZLG=ezxj62R=WkULh2vfpQwqh8P-6FhtONzU7yRbyeuA@mail.gmail.com>
Date:   Tue, 12 Sep 2017 16:03:56 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        David Daney <david.daney@...ium.com>
Cc:     Marc Zyngier <marc.zyngier@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Jassi Brar <jaswinder.singh@...aro.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Jason Cooper <jason@...edaemon.net>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 6/6] gpio: uniphier: add UniPhier GPIO controller driver

On Thu, Sep 7, 2017 at 1:42 PM, Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:

> This GPIO controller device is used on UniPhier SoCs.
>
> It also serves as an interrupt controller, but interrupt signals are
> just delivered to the parent irqchip without any latching or OR'ing.
> This is implemented by using hierarchy IRQ domain.
>
> Implementation note:
> Unfortunately, the IRQ mapping from this controller to the parent is
> random. (48, 49, ..., 63, 154, 155, ...)
> If "interrupts" property is used, IRQ resources may be statically
> allocated when platform devices are populated from DT.  This can be
> a problem for the hierarchy IRQ domain because IRQ allocation must
> happen from the outer-most domain up to the root domain in order to
> build up the stacked IRQ.  (https://lkml.org/lkml/2017/7/6/758)
> Solutions to work around it could be to hard-code parent hwirqs or
> to invent a driver-specific DT property.
>
> Here, the new API irq_domain_push_irq() was merged by v4.14-rc1.
> It allows to add irq_data to the existing hierarchy.  It will help
> to make this driver work whether the parent has already initialized
> the hierarchy or not.
>
> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
> ---
>
> Changes in v4:
>   - Add COMPILE_TEST and select IRQ_DOMAIN_HIERARCHY
>   - Reimplement irqchip part by using irq_domain_push_irq()

Awesome improvement. There was a build error and I also
would like David Daney to have a look at this so we know we
use things the right way, but overall I am happy after this
so I hope I will be able to apply next version.

Yours,
Linus Walleij