linux-kernel - Re: [PATCH v4 1/4] dt-bindings: net: Add Realtek MDIO controller

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Message-ID: <20250122-obedient-owl-from-ganymede-4a8343@krzk-bin>
Date: Wed, 22 Jan 2025 09:12:10 +0100
From: Krzysztof Kozlowski <krzk@...nel.org>
To: Chris Packham <chris.packham@...iedtelesis.co.nz>
Cc: lee@...nel.org, robh@...nel.org, krzk+dt@...nel.org, 
	conor+dt@...nel.org, andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, tsbogend@...ha.franken.de, 
	hkallweit1@...il.com, linux@...linux.org.uk, sander@...nheule.net, 
	markus.stockhausen@....de, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, linux-mips@...r.kernel.org
Subject: Re: [PATCH v4 1/4] dt-bindings: net: Add Realtek MDIO controller

On Mon, Jan 20, 2025 at 05:02:11PM +1300, Chris Packham wrote:
> Add dtschema for the MDIO controller found in the RTL9300 SoCs. The
> controller is slightly unusual in that direct MDIO communication is not
> possible. We model the MDIO controller with the MDIO buses as child
> nodes and the PHYs as children of the buses. Because we do need the
> switch port number to actually communicate over the MDIO bus this needs
> to be supplied via the "realtek,port" property.
> 
> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
> ---
> 
> Notes:
>     Changes in v4:
>     - Model the MDIO controller with the buses as child nodes. We still need
>       to deal with the switch port number so this is represented with the
>       "realtek,port" property which needs to be added to the MDIO bus
>       children (i.e. the PHYs)
>     - Because the above is quite a departure from earlier I've dropped the
>       r-by
>     Changes in v3:
>     - Add r-by from Connor
>     Changes in v2:
>     - None
> 
>  .../bindings/net/realtek,rtl9301-mdio.yaml    | 93 +++++++++++++++++++
>  1 file changed, 93 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
> 
> diff --git a/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml b/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
> new file mode 100644
> index 000000000000..e3ecb1b4afd3
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/realtek,rtl9301-mdio.yaml
> @@ -0,0 +1,93 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/net/realtek,rtl9301-mdio.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Realtek RTL9300 MDIO Controller
> +
> +maintainers:
> +  - Chris Packham <chris.packham@...iedtelesis.co.nz>
> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - enum:
> +              - realtek,rtl9302b-mdio
> +              - realtek,rtl9302c-mdio
> +              - realtek,rtl9303-mdio
> +          - const: realtek,rtl9301-mdio
> +      - const: realtek,rtl9301-mdio
> +
> +  '#address-cells':
> +    const: 1
> +
> +  '#size-cells':
> +    const: 0
> +
> +patternProperties:
> +  '^mdio-bus@[0-4]$':
> +    $ref: mdio.yaml#
> +
> +    properties:
> +      reg:
> +        maxItems: 1
> +
> +    required:
> +      - reg
> +
> +    patternProperties:
> +      '^ethernet-phy(@[a-f0-9]+)?':

Why is the unit address optional?

> +        type: object
> +        $ref: ethernet-phy.yaml#
> +
> +        properties:
> +          realtek,port:
> +            $ref: /schemas/types.yaml#/definitions/uint32
> +            description:
> +              The MDIO communication on the RTL9300 is abstracted by the switch. At
> +              the software level communication uses the switch port to address the
> +              PHY with the actual MDIO bus and address having been setup via the
> +              parent mdio-bus and reg property.

I don't quite get why this cannot be the 'reg' property. I understood that
'reg' of this node is not really used? Or you meant here this 'reg', not
parent's 'reg'?

Best regards,
Krzysztof