linux-kernel - Re: [PATCH] dt-bindings: pci: brcmstb: Add rp1-nexus node to fix DTC warning

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Message-ID: <aKc5nMT1xXpY03ip@apocalypse>
Date: Thu, 21 Aug 2025 17:22:04 +0200
From: Andrea della Porta <andrea.porta@...e.com>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Andrea della Porta <andrea.porta@...e.com>,
	Jim Quinlan <jim2101024@...il.com>,
	Florian Fainelli <florian.fainelli@...adcom.com>,
	Broadcom internal kernel review list <bcm-kernel-feedback-list@...adcom.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>, kwilczynski@...nel.org,
	Manivannan Sadhasivam <mani@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-rpi-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, iivanov@...e.de, svarbanov@...e.de,
	mbrugger@...e.com, Jonathan Bell <jonathan@...pberrypi.com>,
	Phil Elwell <phil@...pberrypi.com>,
	kernel test robot <lkp@...el.com>
Subject: Re: [PATCH] dt-bindings: pci: brcmstb: Add rp1-nexus node to fix DTC
 warning

Hi Krzysztof,

On 10:55 Tue 12 Aug     , Krzysztof Kozlowski wrote:
> On 12/08/2025 10:50, Andrea della Porta wrote:
> > The devicetree compiler is complaining as follows:
> > 
> > arch/arm64/boot/dts/broadcom/rp1-nexus.dtsi:3.11-14.3: Warning (unit_address_vs_reg): /axi/pcie@...0120000/rp1_nexus: node has a reg or ranges property, but no unit name
> > /home/andrea/linux-torvalds/arch/arm64/boot/dts/broadcom/bcm2712-rpi-5-b.dtb: pcie@...0120000: Unevaluated properties are not allowed ('rp1_nexus' was unexpected)
> 
> Please trim the paths.

Ack.

> 
> > 
> > Add the optional node that fix this to the DT binding.
> > 
> > Reported-by: kernel test robot <lkp@...el.com>
> > Closes: https://lore.kernel.org/oe-kbuild-all/202506041952.baJDYBT4-lkp@intel.com/
> > Signed-off-by: Andrea della Porta <andrea.porta@...e.com>
> > ---
> >  Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml | 9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
> > index 812ef5957cfc..7d8ba920b652 100644
> > --- a/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
> > +++ b/Documentation/devicetree/bindings/pci/brcm,stb-pcie.yaml
> > @@ -126,6 +126,15 @@ required:
> >  allOf:
> >    - $ref: /schemas/pci/pci-host-bridge.yaml#
> >    - $ref: /schemas/interrupt-controller/msi-controller.yaml#
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            const: brcm,bcm2712-pcie
> > +    then:
> > +      properties:
> > +        rp1_nexus:
> 
> No, you cannot document post-factum... This does not follow DTS coding
> style.

I think I didn't catch what you mean here: would that mean that
we cannot resolve that warning since we cannot add anything to the
binding?

Regarding rp1_nexus, you're right I guess it should be
rp1-nexus as per DTS coding style.

> 
> Also:
> 
> Node names should be generic. See also an explanation and list of
> examples (not exhaustive) in DT specification:
> https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

In this case it could be difficult: we need to search for a DT node
starting from the DT root and using generic names like pci@0,0 or
dev@0,0 could possibly led to conflicts with other peripherals.
That's why I chose a specific name.

Many thanks,
Andrea

> 
> ... and nodes should be anyway defined in top-level and only customized
> per variant. I am surprised that DTS patch carries a reviewed tag,
> because it was never checked/tested :/
> 
> > +          $ref: /schemas/misc/pci1de4,1.yaml
> >    - if:
> >        properties:
> >          compatible:
> 
> 
> Best regards,
> Krzysztof