smsc75xx: fix phy interrupt acknowledge

smsc75xx phy interrupt acknowledge needs an mdio_write to clear
PHY_INT_SRC instead of just a read like in smsc95xx.

Signed-off-by: Stephane Fillod <fillods@users.sf.net>
Signed-off-by: Steve Glendinning <steve.glendinning@shawell.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/smsc75xx.c

@@ -508,9 +508,10 @@ static int smsc75xx_link_reset(struct usbnet *dev)
 	u16 lcladv, rmtadv;
 	int ret;
 
-	/* clear interrupt status */
+	/* read and write to clear phy interrupt status */
 	ret = smsc75xx_mdio_read(dev->net, mii->phy_id, PHY_INT_SRC);
 	check_warn_return(ret, "Error reading PHY_INT_SRC");
+	smsc75xx_mdio_write(dev->net, mii->phy_id, PHY_INT_SRC, 0xffff);
 
 	ret = smsc75xx_write_reg(dev, INT_STS, INT_STS_CLEAR_ALL);
 	check_warn_return(ret, "Error writing INT_STS");
@@ -643,7 +644,7 @@ static int smsc75xx_set_mac_address(struct usbnet *dev)
 
 static int smsc75xx_phy_initialize(struct usbnet *dev)
 {
-	int bmcr, timeout = 0;
+	int bmcr, ret, timeout = 0;
 
 	/* Initialize MII structure */
 	dev->mii.dev = dev->net;
@@ -672,9 +673,10 @@ static int smsc75xx_phy_initialize(struct usbnet *dev)
 		ADVERTISE_ALL | ADVERTISE_CSMA | ADVERTISE_PAUSE_CAP |
 		ADVERTISE_PAUSE_ASYM);
 
-	/* read to clear */
-	smsc75xx_mdio_read(dev->net, dev->mii.phy_id, PHY_INT_SRC);
-	check_warn_return(bmcr, "Error reading PHY_INT_SRC");
+	/* read and write to clear phy interrupt status */
+	ret = smsc75xx_mdio_read(dev->net, dev->mii.phy_id, PHY_INT_SRC);
+	check_warn_return(ret, "Error reading PHY_INT_SRC");
+	smsc75xx_mdio_write(dev->net, dev->mii.phy_id, PHY_INT_SRC, 0xffff);
 
 	smsc75xx_mdio_write(dev->net, dev->mii.phy_id, PHY_INT_MASK,
 		PHY_INT_MASK_DEFAULT);