net: stmmac: Speed down the PHY if WoL to save energy

When WoL is enabled and the machine is powered off, the PHY remains
waiting for wakeup events at max speed, which is a waste of energy.

Slow down the PHY speed before stopping the ethernet if WoL is enabled,
Signed-off-by: Jisheng Zhang <Jisheng.Zhang@synaptics.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -2823,6 +2823,8 @@ static int stmmac_open(struct net_device *dev)
 	stmmac_init_coalesce(priv);
 
 	phylink_start(priv->phylink);
+	/* We may have called phylink_speed_down before */
+	phylink_speed_up(priv->phylink);
 
 	/* Request the IRQ lines */
 	ret = request_irq(dev->irq, stmmac_interrupt,
@@ -2896,6 +2898,8 @@ static int stmmac_release(struct net_device *dev)
 	if (priv->eee_enabled)
 		del_timer_sync(&priv->eee_ctrl_timer);
 
+	if (device_may_wakeup(priv->device))
+		phylink_speed_down(priv->phylink, false);
 	/* Stop and disconnect the PHY */
 	phylink_stop(priv->phylink);
 	phylink_disconnect_phy(priv->phylink);
@@ -5095,6 +5099,8 @@ int stmmac_suspend(struct device *dev)
 	} else {
 		mutex_unlock(&priv->lock);
 		rtnl_lock();
+		if (device_may_wakeup(priv->device))
+			phylink_speed_down(priv->phylink, false);
 		phylink_stop(priv->phylink);
 		rtnl_unlock();
 		mutex_lock(&priv->lock);
@@ -5207,6 +5213,8 @@ int stmmac_resume(struct device *dev)
 	if (!device_may_wakeup(priv->device) || !priv->plat->pmt) {
 		rtnl_lock();
 		phylink_start(priv->phylink);
+		/* We may have called phylink_speed_down before */
+		phylink_speed_up(priv->phylink);
 		rtnl_unlock();
 	}