linux-kernel - Re: [PATCH v2] of/irq: Ignore interrupt parent for nodes without interrupts

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Message-ID: <CAMuHMdXgq=Zv3GQes_d_eyCcB7m--PaEGSQJtUWiRjj-7gBVkw@mail.gmail.com>
Date: Wed, 19 Nov 2025 09:53:13 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>, 
	Saravana Kannan <saravanak@...gle.com>, 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>, 
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>, 
	Magnus Damm <magnus.damm@...il.com>, devicetree@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org, linux-riscv@...ts.infradead.org, 
	linux-kernel@...r.kernel.org, Marek Szyprowski <m.szyprowski@...sung.com>, 
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>
Subject: Re: [PATCH v2] of/irq: Ignore interrupt parent for nodes without interrupts

On Tue, 18 Nov 2025 at 20:55, Krzysztof Kozlowski <krzk@...nel.org> wrote:
> On 18/11/2025 20:34, Mark Brown wrote:
> > On Fri, Nov 14, 2025 at 11:47:54AM +0100, Geert Uytterhoeven 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:
> >
> > I'm seeing a boot regression on the TI x15 platform in -next which
> > bisects to this patch in -next, unfortunately even with earlycon (though
> > just earlycon, I don't know the platform specific runes) the board just
> > dies with no output:
> >
> >   https://validation.linaro.org/scheduler/job/4252918#L409
> >
> > It does seem like a plausible patch for this sort of issue though, and
> > the bisect converges smoothly:
>
> All Samsung platforms fail as well. I was waiting with bisection but
> Marek was as usually very fast:
>
> https://lore.kernel.org/all/20251118115037.1866871-1-m.szyprowski@samsung.com/

Yeah, the various ti,omap[45]-wugen-mpu nodes have interrupt-parent
properties, but no interrupts{-extended} properties.

Does the following (whitespace-damaged) patch, to restore finding an
explicit interrupt-parent, fix the issue?

--- a/drivers/of/irq.c
+++ b/drivers/of/irq.c
@@ -685,6 +685,8 @@ void __init of_irq_init(const struct of_device_id *matches)
                desc->interrupt_parent = of_parse_phandle(np,
"interrupts-extended", 0);
                if (!desc->interrupt_parent && of_property_present(np,
"interrupts"))
                        desc->interrupt_parent = of_irq_find_parent(np);
+               if (!desc->interrupt_parent)
+                       desc->interrupt_parent = of_parse_phandle(np,
"interrupt-parent", 0);
                if (desc->interrupt_parent == np) {
                        of_node_put(desc->interrupt_parent);
                        desc->interrupt_parent = NULL;

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