Re: Clause 45 and Clause 22 PHYs on one MDIO bus

[Andrew Lunn <andrew@lunn.ch>]

On Mon, Mar 21, 2022 at 10:51:29PM +0100, Michael Walle wrote:
> Am 2022-03-21 21:21, schrieb Andrew Lunn:
> > On Mon, Mar 21, 2022 at 12:21:48PM +0100, Michael Walle wrote:
> > > The SoC I'm using is the LAN9668, which uses the mdio-mscc-mdio
> > > driver.
> > > First problem there, it doesn't support C45 (yet) but also doesn't
> > > check
> > > for MII_ADDR_C45 and happily reads/writes bogus registers.
> > 
> > There are many drivers like that :-(
> > 
> > Whenever a new driver is posted, it is one of the things i ask
> > for. But older drivers are missing such checks.
> 
> Should that be a patch for net or net-next? One thing to consider;
> The gpy215 is probing just fine with a c22 only mdio driver which doesn't
> check for c45 accesses. It might read fishy registers during its probe,
> though. After adding the c45 check in the mdio drivers read and write
> it will fail to probe. So depending on the mdio driver it might went
> unnoticed that the phy_get_c45_ids() could fail.
> 
> If it should go via net, then it should probably be accompanied
> by a patch to fix the gpy_probe() (i.e. ignoring -EOPNOTSUPP
> error).

I would suggest net-next first, so it gets some testing. We can then
add it to net later. We just need to keep an eye out for the automagic
bots which magically pick patches to backport. We don't want them to
pickup these patches too soon and only take part of the fix.

       Andrew