Re: [PATCH net-next 3/3] net: phy: bcm54140: add hwmon support

[Michael Walle]

Am 2020-04-20 17:36, schrieb Andrew Lunn:
> > Ok I see, but what locking do you have in mind? We could have 
> > something
> > like
> >
> > __phy_package_write(struct phy_device *dev, u32 regnum, u16 val)
> > {
> >   return __mdiobus_write(phydev->mdio.bus, phydev->shared->addr,
> >                          regnum, val);
> > }
> >
> > and its phy_package_write() equivalent. But that would just be
> > convenience functions, nothing where you actually help the user with
> > locking. Am I missing something?
>
> In general, drivers should not be using __foo functions. We want
> drivers to make use of phy_package_write() which would do the bus
> locking. Look at a typical PHY driver. There is no locking what so
> ever. Just lots of phy_read() and phy write(). The locking is done by
> the core and so should be correct.

Ok, but for example the BCM54140 uses indirect register access and thus
need to lock the mdio bus itself in which case I need the __funcs.

> > > > > Get the core to do reference counting on the structure?
> > > > > Add helpers phy_read_shared(), phy_write_shared(), etc, which does
> > > > > MDIO accesses on the base device, taking care of the locking.
> > > > >
> > > > The "base" access is another thing, I guess, which has nothing to do
> > > > with the shared structure.
> > > >
> > > I'm making the assumption that all global addresses are at the base
> > > address. If we don't want to make that assumption, we need the change
> > > the API above so you pass a cookie, and all PHYs need to use the same
> > > cookie to identify the package.
> >
> > how would a phy driver deduce a common cookie? And how would that be a
> > difference to using a PHY address.
>
> For a cookie, i don't care how the driver decides on the cookie. The
> core never uses it, other than comparing cookies to combine individual
> PHYs into a package. It could be a PHY address. It could be the PHY
> address where the global registers are. Or it could be anything else.
>
> > > Maybe base is the wrong name, since MSCC can have the base as the high
> > > address of the four, not the low?
> >
> > I'd say it might be any of the four addresses as long as it is the 
> > same
> > across the PHYs in the same package. And in that case you can also 
> > have
> > the phy_package_read/write() functions.
>
> Yes. That is the semantics which is think is most useful. But then we
> don't have a cookie, the value has real significance, and we need to
> document what is should mean.

Agreed.

I will post a RFC shortly.

-michael