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

Andrew Lunn
2023-09-13T01:21:56Z

> > 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.

Andrew