linux-kernel - Re: [PATCH v3 7/8] soc: renesas: Add support for Renesas RZ/N1 GPIO Interrupt Multiplexer

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Message-ID: <20250919173011.4b32a928@bootlin.com>
Date: Fri, 19 Sep 2025 17:30:11 +0200
From: Herve Codina <herve.codina@...tlin.com>
To: Wolfram Sang <wsa+renesas@...g-engineering.com>
Cc: Thomas Gleixner <tglx@...utronix.de>, Hoan Tran
 <hoan@...amperecomputing.com>, Linus Walleij <linus.walleij@...aro.org>,
 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 v3 7/8] soc: renesas: Add support for Renesas RZ/N1 GPIO
 Interrupt Multiplexer

Hi Wolfram,

On Fri, 19 Sep 2025 16:40:06 +0200
Wolfram Sang <wsa+renesas@...g-engineering.com> wrote:

> > Rob asked to use only interrupt-map and use directly the interrupt-map index as
> > the hardware index:
> >   https://lore.kernel.org/lkml/20250801111753.382f52ac@bootlin.com/  
> 
> I agree with that. Currently an interrupt-map entry looks like:
> 
> 	interrupt-map = <0 &gic GIC_SPI 103 IRQ_TYPE_LEVEL_HIGH>,
> 
> And the number after GIC_SPI determines the index register, no? Can't we
> simply say 'index = <SPI_nr_from_dt> - 103' incl. some sanity checks?
> 

And so 103 used to compute the index is hardcoded on the driver.

Further more the wiring of irq-mux interrupt output to the GIC input
line depends on the irq-mux integration and not the irq-mux itself.
Nothing in the irq-mux itself requires a specific connection to the
GIC.

But well, without adding this mapping information in the DT, maybe a
table in the driver in order to determine reg index from GIC IRQ number.

kind of:
  static u8 reg_index[8] = {103, 104, 105, ... , 110};

Base on GIC IRQ number retrieve from the interrupt-map item, we search for
the index in reg_index that match this number. The index found is the index
used to access the register.

What do you think about this?

Best regards,
Hervé