Re: [PATCH net-next v3 0/5] net: stmmac: Add support for Allwinner A733 GMAC210

[Jerome Brunet <jbrunet@baylibre.com>]

On jeu. 24 sept. 2026 at 14:54, Andrew Lunn <andrew@lunn.ch> wrote:

>> I've changed the phy-mode to plain rgmii which seems more in line with
>> what the PHY actually does.
>
> No, it is much messier than that.
>
> https://elixir.bootlin.com/linux/v6.15/source/Documentation/devicetree/bindings/net/ethernet-controller.yaml#L287
>
> rgmii-id is very likely to be correct, if you were using a sane PHY.

It is not the PCB doing the delays so rgmii-id it is (in DT) - got it.

I dunno what is sane or not, but the allwinner dwmac drivers do set some
delays. sun8i-dwmac and sun55i-dwmac do so, even before this change.

If I understand correctly :

"""
When the MAC implements the delay, it must ensure that the PHY does not
also implement the same delay. So it must modify the phy-mode it passes
to the PHY, removing the delay it has added. Failure to remove the delay
will result in a non-functioning link
"""

IOW when the gmac has *-internal-delay-ps set and honors them, it should
also amend phymode seen by PHY to make sure it does not add its own
delays, should it ever be fixed ?

>
> But this PHY is going to cause you lots of problems.

We don't get to choose I'm afraid :)

>
>     Andrew
>

-- 
Jerome