Re: [PATCH net-next v3 02/11] net: phy: introduce phy_has_c45_registers()

From: Michael Walle
Date: Tue Aug 01 2023 - 10:47:14 EST

Hi Andrew,

Am 2023-07-19 09:11, schrieb Michael Walle:
diff --git a/drivers/net/phy/phy-core.c b/drivers/net/phy/phy-core.c
index a64186dc53f8..686a57d56885 100644
--- a/drivers/net/phy/phy-core.c
+++ b/drivers/net/phy/phy-core.c
@@ -556,7 +556,7 @@ int __phy_read_mmd(struct phy_device *phydev, int devad, u32 regnum)

if (phydev->drv && phydev->drv->read_mmd) {
val = phydev->drv->read_mmd(phydev, devad, regnum);
- } else if (phydev->is_c45) {
+ } else if (phy_has_c45_registers(phydev)) {

This i would say should be

phy_has_c45_transfers(phydev). This is about, can we do C45 transfers
on the bus, and if not, fall back to C45 over C22.

Shouldn't this then be a bus property? I.e. mdiobus_has_c45_transfers().
I've have a similar helper introduced in 9/11:

static inline bool mdiobus_supports_c45(struct mii_bus *bus)
return bus->read_c45 && !bus->prevent_c45_access;

static int phylink_sfp_connect_phy(void *upstream, struct phy_device *phy)
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 11c1e91563d4..fdb3774e99fc 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -766,6 +766,11 @@ static inline struct phy_device *to_phy_device(const struct device *dev)
return container_of(to_mdio_device(dev), struct phy_device, mdio);

+static inline bool phy_has_c45_registers(struct phy_device *phydev)
+ return phydev->is_c45;

And this is where it gets interesting. I think as a first step, you
should implement the four functions:


based on this. So there is initially no functional change.

You can then change the implementation of _transfers() based on what
the MDIO bus can do, plus the quirk for if a FUBAR microchip PHY has
been found.

See above. Shouldn't it be mdiobus_...() then?

Then change the implementation of _registers() based on the results of
probing for the ID registers.

So this is where I cannot follow. Right now there is
(1) probing via bus scan
(2) probing via DT (or maybe also ACPI)

With (1) you we have scan_c22(), so if successful, phy_has_c22_registers()
will return true, right? But it's not that clear for
phy_has_c45_registers(), because sometimes we prevent that scan. So
the PHY might have c45 but we don't know.

For (2) we don't even do a c22 scan if we know if its a C45 PHY (or the
other way around). I'm not sure we can reliably tell (at the end of this
series) if a phy has c22 register, c45 registers or both.

Any news here?