linux-kernel - Re: [PATCH v2 2/4] dt-bindings: PCI: mediatek,mt7621: add missing child node reg

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Message-ID: <20240410212638.GA2159326@bhelgaas>
Date: Wed, 10 Apr 2024 16:26:38 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
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Subject: Re: [PATCH v2 2/4] dt-bindings: PCI: mediatek,mt7621: add missing
 child node reg

On Wed, Apr 10, 2024 at 08:15:19PM +0200, Krzysztof Kozlowski wrote:
> MT7621 PCI host bridge has children which apparently are also PCI host
> bridges, at least that's what the binding suggest.

What does it even mean for a PCI host bridge to have a child that is
also a PCI host bridge?

Does this mean a driver binds to the "parent" host bridge, enumerates
the PCI devices below it, and finds a "child" host bridge?

> The children have
> "reg" property, but do not explicitly define it.  Instead they rely on
> pci-bus.yaml schema, but that one has "reg" without any constraints.
> 
> Define the "reg" for the children, so the binding will be more specific
> and later will allow dropping reference to deprecated pci-bus.yaml
> schema.
> 
> Acked-by: Sergio Paracuellos <sergio.paracuellos@...il.com>
> Acked-by: Rob Herring <robh@...nel.org>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> 
> ---
> 
> Changes in v2:
> 1. Add tags.
> ---
>  .../devicetree/bindings/pci/mediatek,mt7621-pcie.yaml          | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/pci/mediatek,mt7621-pcie.yaml b/Documentation/devicetree/bindings/pci/mediatek,mt7621-pcie.yaml
> index e63e6458cea8..61d027239910 100644
> --- a/Documentation/devicetree/bindings/pci/mediatek,mt7621-pcie.yaml
> +++ b/Documentation/devicetree/bindings/pci/mediatek,mt7621-pcie.yaml
> @@ -36,6 +36,9 @@ patternProperties:
>      $ref: /schemas/pci/pci-bus.yaml#
>  
>      properties:
> +      reg:
> +        maxItems: 1
> +
>        resets:
>          maxItems: 1
>  
> -- 
> 2.34.1
>