[PATCH 1/4] ARM: dts: imx6qdl-sabrelite: add mdio phy address 0

[Fabio Estevam]

Adding Gary.

On Mon, May 11, 2026 at 7:15 PM Andrew Lunn <andrew at lunn.ch> wrote:
>
> On Mon, May 11, 2026 at 05:04:56PM -0400, Frank Li wrote:
> > According to IEEE 802.3 Clause 22.2.4.5.5 PHYAD (PHY Address), A PHY that
> > is connected to the station management entity via the mechanical interface
> > defined in 22.6 shall always respond to transactions addressed to PHY
> > Address zero <00000>.
>
> Did you read 22.6? I've not seen a mechanical interface as defined in
> 22.6 for at least 20 years, maybe 30 years.
>
> That cause does not apply in this context.
>
> > -             ethphy: ethernet-phy {
> > +             ethphy: ethernet-phy at 0 {
> >                       compatible = "ethernet-phy-ieee802.3-c22";
> > +                     reg = <0>;
>
> This could very well break this board. Without a reg value, the core
> will find the first PHY on the bus, at whatever address it is at. If
> you hard code 0, the PHY must be at 0, otherwise it will not be found.

On this board, U-Boot checks for the Ethernet PHY at addresses 4, 5, 6, and 7:

https://github.com/u-boot/u-boot/blob/master/board/boundary/nitrogen6x/nitrogen6x.c#L287-L296

In this case, shouldn't U-Boot fix up the Ethernet PHY address accordingly?

Something like mx6cuboxi does:

https://github.com/u-boot/u-boot/blob/master/board/solidrun/mx6cuboxi/mx6cuboxi.c#L414-L446