linux-kernel - Re: linux-next: build warning after merge of the reset tree

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Message-ID: <20241025082817.28056f52@bootlin.com>
Date: Fri, 25 Oct 2024 08:28:17 +0200
From: Herve Codina <herve.codina@...tlin.com>
To: Stephen Rothwell <sfr@...b.auug.org.au>
Cc: Philipp Zabel <p.zabel@...gutronix.de>, Linux Kernel Mailing List
 <linux-kernel@...r.kernel.org>, Linux Next Mailing List
 <linux-next@...r.kernel.org>, Rob Herring <robh@...nel.org>
Subject: Re: linux-next: build warning after merge of the reset tree

Hi all,

On Fri, 25 Oct 2024 11:09:19 +1100
Stephen Rothwell <sfr@...b.auug.org.au> wrote:

> Hi all,
> 
> After merging the reset tree, today's linux-next build (x86_64
> allmodconfig) produced this warning:
> 
> drivers/misc/lan966x_pci.dtso:34.23-40.7: Warning (interrupts_property): /fragment@..._overlay__/pci-ep-bus@...ic@...c0120: Missing interrupt-parent
> 
> Introduced by commit
> 
>   185686beb464 ("misc: Add support for LAN966x PCI device")
> 

This warning is normal.
interrupt-parent is not present in the oic node. This was discussed in
https://lore.kernel.org/all/CAL_Jsq+je7+9ATR=B6jXHjEJHjn24vQFs4Tvi9=vhDeK9n42Aw@mail.gmail.com/

interrupt-parent is not mandatory for a node and if interrupt-parent is not
present, the interrupt parent resolution code will look at the parent node
recursively until an interrupt-parent or an interrupt controller is found.
https://elixir.bootlin.com/linux/v6.12-rc1/source/drivers/of/irq.c#L56

In the LAN966x PCI case, this goes up to the PCI device which is itself an
interrupt controller. This interrupt controller is not described in the dtso
because it is the node where the dtso is applied.

The LAN966x PCI device DT node has the #interrupt-cells and the
interrupt-controller properties. This build at runtime:
https://elixir.bootlin.com/linux/v6.12-rc1/source/drivers/pci/of_property.c#L186

Best regards,
Hervé
-- 
Hervé Codina, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com