Re: [PATCH v3 1/3] dt-bindings: net: Add Realtek MDIO controller

[Chris Packham]

Hi Daniel,

On 18/12/2024 12:54, Daniel Golle wrote:
> On Wed, Dec 18, 2024 at 11:44:59AM +1300, Chris Packham wrote:
> > [...]
> > +patternProperties:
> > +  '^ethernet-phy(@[a-f0-9]+)?':
> > +    type: object
> > +    $ref: ethernet-phy.yaml#
> > +
> > +    properties:
> > +      reg:
> > +        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
> > +          realtek,smi-address property.
> > +
> > +      realtek,smi-address:
> > +        $ref: /schemas/types.yaml#/definitions/uint32-array
> > +        description: SMI interface and address for the connected PHY
> > +        items:
> > +          - description: SMI interface number associated with the port.
> > +          - description: SMI address of the PHY for the port.
> What speaks against describing the actual MDIO busses and addresses (ie.
> the hardware) in Device Tree and setting up the hardware mapping between
> ports and SMI bus and address by parsing the DSA switch port description
> in the MDIO driver?
>
> In that way you would not need the additional vendor-specific property
> and on switches with high port density also avoid having to deal with
> bogus "MDIO addresses" greater than 31.

I kind of expected this discussion.

The main problem is I couldn't figure out how to make that work. 
Ultimately I still need to write the MDIO bus arrangement to hardware 
and map back to a port number when doing MDIO accesses. Whether the 
device-tree uses port number as the reg property and a vendor property 
for the SMI address or does it the other way round I'd still need a 
vendor property. There's also a complication that I've got one MDIO 
controller that looks after more than one MDIO interface at the same 
time. I'll have a bit of a think about it over the holidays and see if I 
can come up with anything cleaner.