Some MDIO busses require to program PHY polling registers depending on
the PHY type. RealTek switch SoCs are the most prominent example of a
DSA switch which doesn't allow to program MAC speed, duplex and
flow-control settings without using PHY polling to do so.

Hence there is a need to inform the MDIO bus driver that a PHY has been
registered on the bus, as otherwise the bus driver will have to reinvent
and duplicate all the bus scanning logic for Clause-22 and Clause-45
PHYs, and discover their features (or maintain a long list of PHY IDs).

Provide a simple hook in struct mii_bus which is called right after a
PHY has been fully probed.

Alternative ways which would allow to do the same things without
having to change any kernel code would of course be very welcome.

Link: https://github.com/openwrt/openwrt/pull/21515#discussion_r2714069716
Signed-off-by: Daniel Golle <daniel@makrotopia.org>
---
 drivers/net/phy/phy_device.c | 8 +++++++-
 include/linux/phy.h          | 3 +++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index f624218bf3664..7807f3db50507 100644
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c

@@ -3778,8 +3778,14 @@ static int phy_probe(struct device *dev)
 	/* Get the LEDs from the device tree, and instantiate standard
 	 * LEDs for them.
 	 */
-	if (IS_ENABLED(CONFIG_PHYLIB_LEDS) && !phy_driver_is_genphy(phydev))
+	if (IS_ENABLED(CONFIG_PHYLIB_LEDS) && !phy_driver_is_genphy(phydev)) {
 		err = of_phy_leds(phydev);
+		if (err)
+			goto out;
+	}
+
+	if (phydev->mdio.bus->register_phy)
+		err = phydev->mdio.bus->register_phy(phydev);
 
 out:
 	/* Re-assert the reset signal on error */

diff --git a/include/linux/phy.h b/include/linux/phy.h
index 5972f19af16da..1d38e27d20389 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h

@@ -377,6 +377,9 @@ struct mii_bus {
 	/** @reset: Perform a reset of the bus */
 	int (*reset)(struct mii_bus *bus);
 
+	/** @register_phy: Called for each PHY detected on the bus */
+	int (*register_phy)(struct phy_device *phydev);
+
 	/** @stats: Statistic counters per device on the bus */
 	struct mdio_bus_stats stats[PHY_MAX_ADDR];
 

-- 
2.52.0