net/phy: fix DP83865 phy interrupt handler

According to the DP83865 datasheet we need to clear
the interrupt status bit by writing a 1 to the
corresponding bit in INT_CLEAR (2:0 are reserved).

Proposed and tested by Thorsten.
Signed-off-by: Thorsten Schubert <tshu@msc-ge.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/national.c

@@ -25,8 +25,9 @@
 /* DP83865 phy identifier values */
 #define DP83865_PHY_ID	0x20005c7a
 
-#define DP83865_INT_MASK_REG 0x15
-#define DP83865_INT_MASK_STATUS 0x14
+#define DP83865_INT_STATUS	0x14
+#define DP83865_INT_MASK	0x15
+#define DP83865_INT_CLEAR	0x17
 
 #define DP83865_INT_REMOTE_FAULT 0x0008
 #define DP83865_INT_ANE_COMPLETED 0x0010
@@ -68,21 +69,25 @@ static int ns_config_intr(struct phy_device *phydev)
 	int err;
 
 	if (phydev->interrupts == PHY_INTERRUPT_ENABLED)
-		err = phy_write(phydev, DP83865_INT_MASK_REG,
+		err = phy_write(phydev, DP83865_INT_MASK,
 				DP83865_INT_MASK_DEFAULT);
 	else
-		err = phy_write(phydev, DP83865_INT_MASK_REG, 0);
+		err = phy_write(phydev, DP83865_INT_MASK, 0);
 
 	return err;
 }
 
 static int ns_ack_interrupt(struct phy_device *phydev)
 {
-	int ret = phy_read(phydev, DP83865_INT_MASK_STATUS);
+	int ret = phy_read(phydev, DP83865_INT_STATUS);
 	if (ret < 0)
 		return ret;
 
-	return 0;
+	/* Clear the interrupt status bit by writing a “1”
+	 * to the corresponding bit in INT_CLEAR (2:0 are reserved) */
+	ret = phy_write(phydev, DP83865_INT_CLEAR, ret & ~0x7);
+
+	return ret;
 }
 
 static void ns_giga_speed_fallback(struct phy_device *phydev, int mode)