Re: [PATCH 0/5] Support both Ethernet interfaces on i.MX6UL and i.MX7

[Peter Maydell]

On Wed, 15 Mar 2023 at 14:52, Guenter Roeck <linux@roeck-us.net> wrote:
>
> The SOC on i.MX6UL and i.MX7 has 2 Ethernet interfaces. The PHY on each may
> be connected to separate MDIO busses, or both may be connected on the same
> MDIO bus using different PHY addresses. Commit 461c51ad4275 ("Add a phy-num
> property to the i.MX FEC emulator") added support for specifying PHY
> addresses, but it did not provide support for linking the second PHY on
> a given MDIO bus to the other Ethernet interface.
>
> To be able to support two PHY instances on a single MDIO bus, two properties
> are needed: First, there needs to be a flag indicating if the MDIO bus on
> a given Ethernet interface is connected. If not, attempts to read from this
> bus must always return 0xffff. Implement this property as phy-connected.
> Second, if the MDIO bus on an interface is active, it needs a link to the
> consumer interface to be able to provide PHY access for it. Implement this
> property as phy-consumer.

So I was having a look at this to see if it was reasonably easy to
split out the PHY into its own device object, and I'm a bit confused.
I know basically 0 about MDIO, but wikipedia says that MDIO buses
have one master (the ethernet MAC) and potentially multiple PHYs.
However it looks like this patchset has configurations where
multiple MACs talk to the same MDIO bus. Am I confused about the
patchset, about the hardware, or about what MDIO supports?

thanks
-- PMM