Re: [PATCH net-next 4/5] phy: net: introduce phy_promote_to_c45()

[Michael Walle]

Am 2023-01-21 00:20, schrieb Russell King (Oracle):
> On Fri, Jan 20, 2023 at 11:40:10PM +0100, Michael Walle wrote:
> > If not explitly asked to be probed as a C45 PHY, on a bus which is
> > capable of doing both C22 and C45 transfers, C45 PHYs are first tried 
> > to
> > be probed as C22 PHYs. To be able to promote the PHY to be a C45 one,
> > the driver can call phy_promote_to_c45() in its probe function.
> >
> > This was already done in the mxl-gpy driver by the following snippet:
> >
> >    if (!phydev->has_c45) {
> >            ret = phy_get_c45_ids(phydev);
> >            if (ret < 0)
> >                    return ret;
> >    }
> >
> > Move that code into the core by creating a new function
> > phy_promote_to_c45(). If a PHY is promoted, C45-over-C22 access is 
> > used,
> > regardless if the bus supports C45 or not. That is because there might
> > be C22 PHYs on the bus which gets confused by C45 accesses.
>
> It is my understanding that C45 PHYs do not have to respond to C22
> accesses. So, wouldn't this lead to some C45 PHYs not being detected?

In that case, the PHY already has to be a C45 PHY, correct? Because
no access to c22 means, it can't be probed as a c22 phy; therefore,
it has the has_c45 set to true. Then phy_promote_to_c45() is a noop and
c45-over-c22 wont be set.

-michael