net: dsa: mv88e6xxx: Add watchdog interrupt handler

The switch contains a watchdog looking for issues with the internal
gubbins of the switch. Hook the interrupt the watchdog triggers and
log the value of the control register indicating why the watchdog
fired. The watchdog can only be cleared with a switch reset, which
will destroy the current configuration. Rather than doing this, just
disable the interrupt.

The mv88e6390 family has different watchdog registers. So use an ops
structure, so support for the mv88e6390 family can be added later.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mv88e6xxx/global2.h

@@ -46,6 +46,8 @@ int mv88e6xxx_g2_irq_setup(struct mv88e6xxx_chip *chip);
 void mv88e6xxx_g2_irq_free(struct mv88e6xxx_chip *chip);
 int mv88e6095_g2_mgmt_rsvd2cpu(struct mv88e6xxx_chip *chip);
 
+extern const struct mv88e6xxx_irq_ops mv88e6097_watchdog_ops;
+
 #else /* !CONFIG_NET_DSA_MV88E6XXX_GLOBAL2 */
 
 static inline int mv88e6xxx_g2_require(struct mv88e6xxx_chip *chip)
@@ -125,6 +127,8 @@ static inline int mv88e6095_g2_mgmt_rsvd2cpu(struct mv88e6xxx_chip *chip)
 	return -EOPNOTSUPP;
 }
 
+static const struct mv88e6xxx_irq_ops mv88e6097_watchdog_ops = {};
+
 #endif /* CONFIG_NET_DSA_MV88E6XXX_GLOBAL2 */
 
 #endif /* _MV88E6XXX_GLOBAL2_H */