Hi Florian, Doug,

I'm currently trying to make the RaspberryPi CM4 IO board probe its
ethernet controller, and it looks like genet doesn't manage to find its
PHY and errors out with:

[    3.240435] libphy: Fixed MDIO Bus: probed
[    3.248849] bcmgenet fd580000.ethernet: GENET 5.0 EPHY: 0x0000
[    3.259118] libphy: bcmgenet MII bus: probed
[    3.278420] mdio_bus unimac-mdio--19: MDIO device at address 1 is missing.
[    3.285661] unimac-mdio unimac-mdio.-19: Broadcom UniMAC MDIO bus

....

[   13.082281] could not attach to PHY
[   13.089762] bcmgenet fd580000.ethernet eth0: failed to connect to PHY
[   74.739621] could not attach to PHY
[   74.746492] bcmgenet fd580000.ethernet eth0: failed to connect to PHY

Here's the full boot log:
https://pastebin.com/8RhuezSn

It looks like it's related to the following bugzilla entry:
https://bugzilla.kernel.org/show_bug.cgi?id=213485

However, that commit has been merged for a while apparently, and even
next-20211022 shows that behavior, both with the drivers built-in or as
modules. The other suggested fix to set probe_type to
PROBE_FORCE_SYNCHRONOUS doesn't seem to fix it either.

Maxime