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

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Message-ID: <CAMuHMdWBGzLmpNeYtSe7SW64X7EQ8chUxrjKQpfhBdz0tHTRdA@mail.gmail.com>
Date: Mon, 6 Oct 2025 09:35:04 +0200
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Rob Herring <robh@...nel.org>
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

Hi Rob,

On Fri, 3 Oct 2025 at 15:33, Rob Herring <robh@...nel.org> wrote:
> 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?

Perhaps you might object to putting interrupt-parent in the root node
if it does not point to the root interrupt controller, or if it does
not help to simplify interrupts-extended to interrupts (like e.g. for
ARM arch timer)?

Thanks!

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds