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SubjectRe: [RFC net-next 0/2] Introduce MDIO probe order C45 over C22
Hi Andrew,

On Thu, Jun 03, 2021 at 07:51:55AM +0800, Wong Vee Khee wrote:
> On Wed, Jun 02, 2021 at 05:03:52PM +0200, Andrew Lunn wrote:
> > > I took a look at how most ethernet drivers implement their "bus->read"
> > > function. Most of them either return -EIO or -ENODEV.
> > >
> > > I think it safe to drop the return error type when we try with C45 access:
> > >
> > >
> > > diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> > > index 1539ea021ac0..282d16fdf6e1 100644
> > > --- a/drivers/net/phy/phy_device.c
> > > +++ b/drivers/net/phy/phy_device.c
> > > @@ -870,6 +870,18 @@ struct phy_device *get_phy_device(struct mii_bus *bus, int addr, bool is_c45)
> > > if (r)
> > > return ERR_PTR(r);
> > >
> > > + /* PHY device such as the Marvell Alaska 88E2110 will return a PHY ID
> > > + * of 0 when probed using get_phy_c22_id() with no error. Proceed to
> > > + * probe with C45 to see if we're able to get a valid PHY ID in the C45
> > > + * space, if successful, create the C45 PHY device.
> > > + */
> > > + if ((!is_c45) && (phy_id == 0)) {
> > > + r = get_phy_c45_ids(bus, addr, &c45_ids);
> > > + if (!r)
> > > + return phy_device_create(bus, addr, phy_id,
> > > + true, &c45_ids);
> > > + }
> >
> > This is getting better. But look at for example
> > drivers/net/mdio/mdio-bcm-unimac.c. What will happen when you ask it
> > to do get_phy_c45_ids()?
> >
>
> I will add an additional check for bus->probe_capabilities. This will ensure
> that only a MDIO bus that is capable for C45 access will go for the 'try getting
> PHY ID from C45 space' approach. Currently, only Freescale's QorIQ 10G MDIO
> Controller driver and STMMAC driver has a bus->probe_capabilities of > MDIOBUS_C45.
> So, I would say with this additional checking, it would not break most of the drivers:-
>
>
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 1539ea021ac0..460c0866ac84 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -870,6 +870,19 @@ struct phy_device *get_phy_device(struct mii_bus *bus, int addr, bool is_c45)
> if (r)
> return ERR_PTR(r);
>
> + /* PHY device such as the Marvell Alaska 88E2110 will return a PHY ID
> + * of 0 when probed using get_phy_c22_id() with no error. Proceed to
> + * probe with C45 to see if we're able to get a valid PHY ID in the C45
> + * space, if successful, create the C45 PHY device.
> + */
> + if ((!is_c45) && (phy_id == 0) &&
> + (bus->probe_capabilities >= MDIOBUS_C45)) {
> + r = get_phy_c45_ids(bus, addr, &c45_ids);
> + if (!r)
> + return phy_device_create(bus, addr, phy_id,
> + true, &c45_ids);
> + }
> +
> return phy_device_create(bus, addr, phy_id, is_c45, &c45_ids);
> }
> EXPORT_SYMBOL(get_phy_device);
>

Can you take a look at the latest implementation and provide
feedback?

VK

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