Re: Race between "Generic PHY" and "bcm53xx" drivers after -EPROBE_DEFER

On Mon, Sep 20, 2021 at 10:14:48AM -0700, Florian Fainelli wrote:

The SPROM is a piece of NVRAM that is intended to describe in a set of
key/value pairs various platform configuration details. There can be up
to 3 GMACs on the SoC which you can connect in a variety of ways towards
internal/external PHYs or internal/external Ethernet switches. The SPROM
is used to describe whether you connect to a regular PHY (not at PHY
address 30 decimal, so not the Broadcom pseudo-PHY) or an Ethernet
switch pseudo-PHY via MDIO.

What appears to be missing here is that we should not be executing this
block of code for phyaddr == BGMAC_PHY_NOREGS because we will not have a
PHY device proper to begin with and this collides with registering the
b53_mdio driver.

Who provisions the SPROM exactly? It still seems pretty broken to me
that one of the GMACs has a bgmac->phyaddr pointing to a switch.
Special-casing the Broadcom switch seems not enough, the same thing
could happen with a Marvell switch or others. How about looking up the
device tree whether the bgmac->mii_bus' OF node has any child with a
"reg" of bgmac->phyaddr, and if it does, whether of_mdiobus_child_is_phy
actually returns true for it?