net: mdio: get/put device node during (un)registration

The __of_mdiobus_register() function was storing the device node in
dev.of_node without increasing its reference count. It implicitly relied
on the caller to maintain the allocated node until the mdiobus was
unregistered.

Now, __of_mdiobus_register() will acquire the node before assigning it,
and of_mdiobus_unregister_callback() will be called at the end of
mdio_unregister().

Drivers can now release the node immediately after MDIO registration.
Some of them are already doing that even before this patch.
Signed-off-by: Luiz Angelo Daros de Luca <luizluca@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/mdio/of_mdio.c

@@ -139,6 +139,11 @@ bool of_mdiobus_child_is_phy(struct device_node *child)
 }
 EXPORT_SYMBOL(of_mdiobus_child_is_phy);
 
+static void __of_mdiobus_unregister_callback(struct mii_bus *mdio)
+{
+	of_node_put(mdio->dev.of_node);
+}
+
 /**
  * __of_mdiobus_register - Register mii_bus and create PHYs from the device tree
  * @mdio: pointer to mii_bus structure
@@ -166,6 +171,8 @@ int __of_mdiobus_register(struct mii_bus *mdio, struct device_node *np,
 	 * the device tree are populated after the bus has been registered */
 	mdio->phy_mask = ~0;
 
+	mdio->__unregister_callback = __of_mdiobus_unregister_callback;
+	of_node_get(np);
 	device_set_node(&mdio->dev, of_fwnode_handle(np));
 
 	/* Get bus level PHY reset GPIO details */
@@ -177,7 +184,7 @@ int __of_mdiobus_register(struct mii_bus *mdio, struct device_node *np,
 	/* Register the MDIO bus */
 	rc = __mdiobus_register(mdio, owner);
 	if (rc)
-		return rc;
+		goto put_node;
 
 	/* Loop over the child nodes and register a phy_device for each phy */
 	for_each_available_child_of_node(np, child) {
@@ -237,6 +244,9 @@ int __of_mdiobus_register(struct mii_bus *mdio, struct device_node *np,
 unregister:
 	of_node_put(child);
 	mdiobus_unregister(mdio);
+
+put_node:
+	of_node_put(np);
 	return rc;
 }
 EXPORT_SYMBOL(__of_mdiobus_register);

drivers/net/phy/mdio_bus.c

@@ -787,6 +787,9 @@ void mdiobus_unregister(struct mii_bus *bus)
 		gpiod_set_value_cansleep(bus->reset_gpiod, 1);
 
 	device_del(&bus->dev);
+
+	if (bus->__unregister_callback)
+		bus->__unregister_callback(bus);
 }
 EXPORT_SYMBOL(mdiobus_unregister);
 

include/linux/phy.h

@@ -434,6 +434,9 @@ struct mii_bus {
 
 	/** @shared: shared state across different PHYs */
 	struct phy_package_shared *shared[PHY_MAX_ADDR];
+
+	/** @__unregister_callback: called at the last step of unregistration */
+	void (*__unregister_callback)(struct mii_bus *bus);
 };
 #define to_mii_bus(d) container_of(d, struct mii_bus, dev)