net: dsa: microchip: use wakeup-source DT property to enable PME output

KSZ switches with WoL support signals wake event over PME pin. If this
pin is attached to some external PMIC or System Controller can't be
described as GPIO, the only way to describe it in the devicetree is to
use wakeup-source property. So, add support for this property and enable
PME switch output if this property is present.
Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <florian.fainelli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/ksz_common.c

@@ -4159,6 +4159,9 @@ int ksz_switch_register(struct ksz_device *dev)
 			dev_err(dev->dev, "inconsistent synclko settings\n");
 			return -EINVAL;
 		}
+
+		dev->wakeup_source = of_property_read_bool(dev->dev->of_node,
+							   "wakeup-source");
 	}
 
 	ret = dsa_register_switch(dev->ds);

drivers/net/dsa/microchip/ksz_common.h

@@ -163,6 +163,7 @@ struct ksz_device {
 	phy_interface_t compat_interface;
 	bool synclko_125;
 	bool synclko_disable;
+	bool wakeup_source;
 
 	struct vlan_table *vlan_cache;