Re: [PATCH v1 03/11] arm64: dts: freescale: imx8mm-var-som: Update FEC support with MaxLinear PHY

[Stefano Radaelli]

Hi Andrew,

On Tue, Feb 17, 2026 at 09:43:16PM +0100, Andrew Lunn wrote:
> 
> And here you loose me. RGMII is between the MAC and the PHY. The PHY
> is on the SOM, so there is no need for RGMII to leave the SOM.
> 
> MDIO is can understand going to the carrier, because there can be
> other devices on the bus, such as an Ethernet switch.
> 
> You say the LEDs are not on the SOM. So they should not be listed in
> the .dtsi file for the SOM. It could be the RJ45 is a cheap one,
> without LEDs. The colours will depend on the RJ45 socket. It could be
> a single LED is connected to the front panel, which is typical of STB
> etc. So the LEDs are a board property, not a SOM property.
> 
> > > >   Two LEDs are defined to match the VAR-SOM carrier design:
> > > >     * LED@0: Yellow, netdev trigger.
> > > >     * LED@1: Green, netdev trigger.
> > > 
> > > Where are the LEDs? You say "carrier design", so are they on the
> > > carrier? The DT properties should then be in the .dts file for the
> > > carrier.
> > >
> > 
> > The LED signals are driven directly by the PHY and originate on the SOM.
> > They are exposed on the SOM connector and are typically routed straight
> > to the RJ45 integrated LEDs on the carrier.
> 
> The problem here is 'typically', not absolutely required, otherwise
> the magic smoke will escape making the box useless.
> 

You are right sorry for the confusion: RGMII is internal between the MAC
and the PHY and does not leave the SOM. What is exposed on the SOM
connector are the MDI pairs towards the magnetics/RJ45 and the PHY LED
output signals.

Given that the actual LEDs are implemented on the carrier side (RJ45
with integrated LEDs, pull-ups and LED supply), would you prefer that
the LED description is moved out of the SOM .dtsi and into the carrier
.dts?

My idea would be to keep the Ethernet controller/PHY node fully
described in the SOM .dtsi (since the PHY is on-module), and add only
the LED subnode/definition in the carrier .dts where the LEDs are
actually present.

If this is the right approach, I will apply the same pattern to the
other Variscite SOMs where we currently describe PHY LEDs at the SOM
level (e.g. imx8mp-var-som, imx93-var-som).

Thanks again for the review.

Best regards,
Stefano