linux-kernel - Re: [PATCH v4 7/8] soc: renesas: Add support for Renesas RZ/N1 GPIO Interrupt Multiplexer

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Message-ID: <CACRpkdZPURiag1cUQZ319_QA83u+qOCSRALxpe10_+cTcevy+Q@mail.gmail.com>
Date: Wed, 1 Oct 2025 13:08:57 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: "Herve Codina (Schneider Electric)" <herve.codina@...tlin.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Wolfram Sang <wsa+renesas@...g-engineering.com>, 
	Hoan Tran <hoan@...amperecomputing.com>, Bartosz Golaszewski <brgl@...ev.pl>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Geert Uytterhoeven <geert+renesas@...der.be>, Magnus Damm <magnus.damm@...il.com>, 
	Saravana Kannan <saravanak@...gle.com>, Serge Semin <fancer.lancer@...il.com>, 
	Phil Edworthy <phil.edworthy@...esas.com>, linux-gpio@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, Pascal Eberhard <pascal.eberhard@...com>, 
	Miquel Raynal <miquel.raynal@...tlin.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v4 7/8] soc: renesas: Add support for Renesas RZ/N1 GPIO
 Interrupt Multiplexer

Hi Herve,

thanks for your patch!

On Mon, Sep 22, 2025 at 5:27 PM Herve Codina (Schneider Electric)
<herve.codina@...tlin.com> wrote:

> On the Renesas RZ/N1 SoC, GPIOs can generate interruptions. Those
> interruption lines are multiplexed by the GPIO Interrupt Multiplexer in
> order to map 32 * 3 GPIO interrupt lines to 8 GIC interrupt lines.
>
> The GPIO interrupt multiplexer IP does nothing but select 8 GPIO
> IRQ lines out of the 96 available to wire them to the GIC input lines.
>
> Signed-off-by: Herve Codina (Schneider Electric) <herve.codina@...tlin.com>

This looks like some complicated code to reimplement hierarchical
irq domains.

Can't you just select IRQ_DOMAIN_HIERARCHY and let
the existing infrastructure in GPIOLIB_IRQCHIP handle
this?

This kind of remapping and handling is exactly what the
.child_to_parent_hwirq() callback in struct gpio_irq_chip
is for. This function can fail if you run out if IRQ lines.

Inspect drivers/gpio/Kconfig driver that select
IRQ_DOMAIN_HIERARCHY for examples of how to
do this.

Even if your GPIO driver is not using GPIOLIB_IRQCHIP (in that
case: why not?) I think you still need to use IRQ_DOMAIN_HIERARCHY
for this.

Yours,
Linus Walleij