linux-kernel - Re: [PATCH 3/4] dt-bindings: net: nxp,s32-dwmac: Use the GPR syscon

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Message-ID: <aT_p_aGfBpyEOC3M@stanley.mountain>
Date: Mon, 15 Dec 2025 13:59:09 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Jan Petrous <jan.petrous@....nxp.com>, s32@....com,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linaro-s32@...aro.org
Subject: Re: [PATCH 3/4] dt-bindings: net: nxp,s32-dwmac: Use the GPR syscon

On Mon, Dec 01, 2025 at 06:33:07PM +0100, Krzysztof Kozlowski wrote:
> On 01/12/2025 14:08, Dan Carpenter wrote:
> > The S32 chipset has a GPR region which has a miscellaneous registers
> > including the GMAC_0_CTRL_STS register.  Originally this code accessed
> > that register in a sort of ad-hoc way, but we want to access it using
> > the syscon interface.
> > 
> > We still need to maintain the old method of accessing the GMAC register
> > but using a syscon will let us access other registers more cleanly.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> > ---
> >  Documentation/devicetree/bindings/net/nxp,s32-dwmac.yaml | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/net/nxp,s32-dwmac.yaml b/Documentation/devicetree/bindings/net/nxp,s32-dwmac.yaml
> > index 2b8b74c5feec..17f6c50dca03 100644
> > --- a/Documentation/devicetree/bindings/net/nxp,s32-dwmac.yaml
> > +++ b/Documentation/devicetree/bindings/net/nxp,s32-dwmac.yaml
> > @@ -32,6 +32,11 @@ properties:
> >        - description: Main GMAC registers
> >        - description: GMAC PHY mode control register
> >  
> > +  phy-sel:
> 
> Missing vendor prefix.
> 
> > +    $ref: /schemas/types.yaml#/definitions/phandle-array
> > +    items:
> > +      - description: The offset into the s32 GPR syscon
> 
> No, first item is not the offset but the phandle. You need syntax like here:
> 
> https://elixir.bootlin.com/linux/v5.18-rc1/source/Documentation/devicetree/bindings/soc/samsung/exynos-usi.yaml#L42
> 
> The description of the first item (unlike in example above) should say
> what is the purpose, how this device is using GPR region, what is it
> needed for.

I had to do it a bit differently from the exynos-usi.yaml code.  When I
tried it that way I got the following warning that the "phy-sel" wasn't
a common suffix and it doesn't have a description.

$ make dt_binding_check DT_SCHEMA_FILES=net/nxp,s32-dwmac.yaml
  SCHEMA  Documentation/devicetree/bindings/processed-schema.json
  CHKDT   ./Documentation/devicetree/bindings
/home/dcarpenter/progs/kernel/nxp_gpr/Documentation/devicetree/bindings/net/nxp,s32-dwmac.yaml: properties:nxp,phy-sel: 'anyOf' conditional failed, one must be fixed:
        'description' is a dependency of '$ref'
        '/schemas/types.yaml#/definitions/phandle-array' does not match '^#/(definitions|\\$defs)/'
                hint: A vendor property can have a $ref to a a $defs schema
        hint: Vendor specific properties must have a type and description unless they have a defined, common suffix.
        from schema $id: http://devicetree.org/meta-schemas/vendor-props.yaml#
  LINT    ./Documentation/devicetree/bindings
  DTEX    Documentation/devicetree/bindings/net/nxp,s32-dwmac.example.dts
  DTC [C] Documentation/devicetree/bindings/net/nxp,s32-dwmac.example.dtb

The exynos-usi.yaml file doesn't generate a warning like that and I wasn't
able to figure out why that is.  But what worked for me was adding the
phandle description like this:

  nxp,phy-sel:
    description: phandle to the GPR syscon node
    $ref: /schemas/types.yaml#/definitions/phandle-array
    items:
      - description: offset of PHY selection register

regards,
dan carpenter