[PATCH 2/4] dt-bindings: net: dsa: document internal MDIO bus

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On 13.09.2023 04:21, Andrew Lunn wrote:
>>> The marvell switch can have up to 2 MDIO busses. If i remember
>>> correctly, there is also one switch which has one MDIO bus per port.
>>
>> I'm writing the json-schema for Marvell switches. I've checked a few
>> devicetree source files on Linus's Linux tree, I only see two buses used at
>> the most.
> 
> Sorry, i was ambiguous. Its not a Marvell switch which can have one
> MDIO bus per port. I don't remember which switch it is, and it might
> be a pure switchdev switch, not a DSA switch.
> 
>> The internal bus and another bus with
>> marvell,mv88e6xxx-mdio-external. I've never seen a devicetree with
>> marvell,mv88e6250 though. Could the switch that has one MDIO bus per port
>> be this one? Also, is every bus of this switch a
>> marvell,mv88e6xxx-mdio-external bus or, one internal bus and the remaining
>> are marvell mv88e6xxx-mdio-external buses?
> 
> Only the 6390 family has two busses. It has an internal MDIO bus with
> the same register API as all the other switches. However, unlike the
> other families, it is not exposed on pins. And the 6390 has a second
> MDIO bus using a slight variant of the registers, which is connected
> to the outside world via pins. This second bus then has a compatible
> to separate it from the normal MDIO bus.

OK, I will disallow the external mdio bus for the compatible strings other
than marvell,mv88e6190.

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