Messages in this thread | | | Date | Mon, 21 Mar 2022 22:41:56 +0100 | From | Michael Walle <> | Subject | Re: Clause 45 and Clause 22 PHYs on one MDIO bus |
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Am 2022-03-21 21:36, schrieb Andrew Lunn: >> Actually, it looks like mdiobus_c45_read() is really c45 only and only >> used for PHYs which just support c45 and not c45-over-c22 (?). I was >> mistaken by the heavy use of the function in phy_device.c. All the >> methods in phy-c45.c use phy_*_mmd() functions. Thus it might only be >> the mxl-gpy doing something fishy in its probe function. > > Yes, there is something odd here. You should search back on the > mailing list. > > If i remember correctly, it is something like it responds to both c22 > and c45. If it is found via c22, phylib does not set phydev->is_c45, > and everything ends up going indirect. So the probe additionally tries > to find it via c45? Or something like that.
Yeah, found it: https://lore.kernel.org/netdev/YLaG9cdn6ewdffjV@lunn.ch/
But that means that if the controller is not c45 capable, it will always fail to probe, no?
I've added the "if (regnum & MII_ADDR_C45) return -EOPNOTSUPP" to the mdio driver and the gpy phy will then fail to probe - as expected.
Should it check for -EOPNOTSUPP and just ignore that error and continue probing? Or make it a no-op if probe_capabilities say it has no c45 access so it would take advantage of a quirk flag (derived from dt)?
>> Nevertheless, I'd still need the opt-out of any c45 access. Otherwise, >> if someone will ever implement c45 support for the mdio-mscc-mdio >> driver, I'll run in the erratic behavior. > > Yah, i need to think about that. Are you purely in the DT world, or is > ACPI also an option?
Just DT world.
> Maybe extend of_mdiobus_register() to look for a DT property to limit > what values probe_capabilities can take?
I'll have to give it a try. First I was thinking that we wouldn't need it because a broken PHY driver could just set a quirk "broken_c45_access" or similar. But that would mean it has to be probed before any c45 PHY. Dunno if that will be true for the future. And it sounds rather fragile. So yes, a dt property might be a better option.
-michael
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