linux-kernel - Re: [PATCH/RFC 1/2] of/irq: Ignore interrupt parent for nodes without interrupts

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Message-ID: <CAL_JsqJACXgfgLBn4bpz9uG2zEsoH+FX+8wHmTSj2rLVV59=hg@mail.gmail.com>
Date: Fri, 3 Oct 2025 08:32:57 -0500
From: Rob Herring <robh@...nel.org>
To: Geert Uytterhoeven <geert+renesas@...der.be>
Cc: Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Paul Walmsley <pjw@...nel.org>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, 
	Alexandre Ghiti <alex@...ti.fr>, Samuel Holland <samuel@...lland.org>, Marc Zyngier <maz@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, Magnus Damm <magnus.damm@...il.com>, 
	linux-renesas-soc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC 1/2] of/irq: Ignore interrupt parent for nodes without interrupts

On Fri, Oct 3, 2025 at 5:08 AM Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
>
> The Devicetree Specification states:
>
>     The root of the interrupt tree is determined when traversal of the
>     interrupt tree reaches an interrupt controller node without an
>     interrupts property and thus no explicit interrupt parent.
>
> However, of_irq_init() gratuitously assumes that a node without
> interrupts has an actual interrupt parent if it finds an
> interrupt-parent property higher up in the device tree.  Hence when such
> a property is present (e.g. in the root node), the root interrupt
> controller may not be detected as such, causing a panic:
>
>     OF: of_irq_init: children remain, but no parents
>     Kernel panic - not syncing: No interrupt controller found.
>
> Commit e91033621d56e055 ("of/irq: Use interrupts-extended to find
> parent") already fixed a first part, by checking for the presence of an
> interrupts-extended property.  Fix the second part by only calling
> of_irq_find_parent() when an interrupts property is present.

Seems reasonable. Why the RFC tag?

Normally I'd worry about some ancient PPC or Sparc system, but they
don't use of_irq_init().

Rob