net: mdio: add mdiobus_c45_read/write_nested helpers

Some DSA devices pass through PHY access to the MDIO bus the switch is
on. Add C45 versions of the current C22 helpers for nested accesses to
MDIO busses, so that C22 and C45 can be separated in these DSA
drivers.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/phy/mdio_bus.c

@@ -1008,6 +1008,33 @@ int mdiobus_c45_read(struct mii_bus *bus, int addr, int devad, u32 regnum)
 }
 EXPORT_SYMBOL(mdiobus_c45_read);
 
+/**
+ * mdiobus_c45_read_nested - Nested version of the mdiobus_c45_read function
+ * @bus: the mii_bus struct
+ * @addr: the phy address
+ * @devad: device address to read
+ * @regnum: register number to read
+ *
+ * In case of nested MDIO bus access avoid lockdep false positives by
+ * using mutex_lock_nested().
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ */
+int mdiobus_c45_read_nested(struct mii_bus *bus, int addr, int devad,
+			    u32 regnum)
+{
+	int retval;
+
+	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
+	retval = __mdiobus_c45_read(bus, addr, devad, regnum);
+	mutex_unlock(&bus->mdio_lock);
+
+	return retval;
+}
+EXPORT_SYMBOL(mdiobus_c45_read_nested);
+
 /**
  * mdiobus_write_nested - Nested version of the mdiobus_write function
  * @bus: the mii_bus struct
@@ -1082,6 +1109,34 @@ int mdiobus_c45_write(struct mii_bus *bus, int addr, int devad, u32 regnum,
 }
 EXPORT_SYMBOL(mdiobus_c45_write);
 
+/**
+ * mdiobus_c45_write_nested - Nested version of the mdiobus_c45_write function
+ * @bus: the mii_bus struct
+ * @addr: the phy address
+ * @devad: device address to read
+ * @regnum: register number to write
+ * @val: value to write to @regnum
+ *
+ * In case of nested MDIO bus access avoid lockdep false positives by
+ * using mutex_lock_nested().
+ *
+ * NOTE: MUST NOT be called from interrupt context,
+ * because the bus read/write functions may wait for an interrupt
+ * to conclude the operation.
+ */
+int mdiobus_c45_write_nested(struct mii_bus *bus, int addr, int devad,
+			     u32 regnum, u16 val)
+{
+	int err;
+
+	mutex_lock_nested(&bus->mdio_lock, MDIO_MUTEX_NESTED);
+	err = __mdiobus_c45_write(bus, addr, devad, regnum, val);
+	mutex_unlock(&bus->mdio_lock);
+
+	return err;
+}
+EXPORT_SYMBOL(mdiobus_c45_write_nested);
+
 /**
  * mdiobus_modify - Convenience function for modifying a given mdio device
  *	register

include/linux/mdio.h

@@ -425,10 +425,14 @@ int mdiobus_modify_changed(struct mii_bus *bus, int addr, u32 regnum,
 			   u16 mask, u16 set);
 int __mdiobus_c45_read(struct mii_bus *bus, int addr, int devad, u32 regnum);
 int mdiobus_c45_read(struct mii_bus *bus, int addr, int devad, u32 regnum);
+int mdiobus_c45_read_nested(struct mii_bus *bus, int addr, int devad,
+			     u32 regnum);
 int __mdiobus_c45_write(struct mii_bus *bus, int addr,  int devad, u32 regnum,
 			u16 val);
 int mdiobus_c45_write(struct mii_bus *bus, int addr,  int devad, u32 regnum,
 		      u16 val);
+int mdiobus_c45_write_nested(struct mii_bus *bus, int addr,  int devad,
+			     u32 regnum, u16 val);
 int mdiobus_c45_modify(struct mii_bus *bus, int addr, int devad, u32 regnum,
 		       u16 mask, u16 set);