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

On Mon, Sep 20, 2021 at 11:10:39AM -0700, Florian Fainelli wrote:

quoted

But even so, what's a "pseudo PHY" exactly? I think that's at the bottom
of this issue. In the Linux device model, a device has a single driver.
In this case, the same MDIO device either has a switch driver, if you
accept it's a switch, or a PHY driver, if you accept it's a PHY.
I said it's "broken" because the expectation seems to be that it's a switch,
but it looks like it's treated otherwise. Simply put, the same device
can't be both a switch and a PHY.

A pseudo-PHY is a device that can snoop and respond to MDIO bus
requests. I understand it cannot be both, just explaining to you how the
people at Broadcom have been seeing the world from their perspective.
Anything that is found at MDIO address 0x1e/30 is considered a MDIO
attached switch, that's all.

Nothing wrong with that per se, at NXP we've been thinking about RevMII
as well, and having a switch expose itself as a PHY over MDIO, in any
case something a bit richer/more interactive than a fixed-link.

One way to bypass that limitation is to access the switch registers
through a different device compared to the PHY device. At the very
least, a different MDIO address. Even better, not over MDIO at all, but
something faster, SPI, PCIe etc.