net: phy: fix PHY_RUNNING in phy_state_machine

commit 11e122cb upstream.

Currently, if phy state is PHY_RUNNING, we always register a CHANGE
when phy works in polling or interrupt ignored, this will make the
adjust_link being called even the phy link did Not changed.

checking the phy link to make sure the link did changed before we
register a CHANGE, if link did not changed, we do nothing.
Signed-off-by: Shaohui Xie <Shaohui.Xie@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/net/phy/phy.c

@@ -740,6 +740,7 @@ void phy_state_machine(struct work_struct *work)
 			container_of(dwork, struct phy_device, state_queue);
 	bool needs_aneg = false, do_suspend = false, do_resume = false;
 	int err = 0;
+	int old_link;
 
 	mutex_lock(&phydev->lock);
 
@@ -823,11 +824,18 @@ void phy_state_machine(struct work_struct *work)
 		phydev->adjust_link(phydev->attached_dev);
 		break;
 	case PHY_RUNNING:
-		/* Only register a CHANGE if we are
-		 * polling or ignoring interrupts
+		/* Only register a CHANGE if we are polling or ignoring
+		 * interrupts and link changed since latest checking.
 		 */
-		if (!phy_interrupt_is_valid(phydev))
-			phydev->state = PHY_CHANGELINK;
+		if (!phy_interrupt_is_valid(phydev)) {
+			old_link = phydev->link;
+			err = phy_read_status(phydev);
+			if (err)
+				break;
+
+			if (old_link != phydev->link)
+				phydev->state = PHY_CHANGELINK;
+		}
 		break;
 	case PHY_CHANGELINK:
 		err = phy_read_status(phydev);