net: lan78xx: Ack pending PHY ints when resetting

lan78xx_link_reset explicitly clears the MAC's view of the PHY's IRQ
status. In doing so it potentially leaves the PHY with a pending
interrupt that will never be acknowledged, at which point no further
interrupts will be generated.

Avoid the problem by acknowledging any pending PHY interrupt after
clearing the MAC's status bit.

See: #2937

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

Author: pelwell

drivers/net/usb/lan78xx.c

@@ -1629,7 +1629,16 @@ static int lan78xx_mac_reset(struct lan78xx_net *dev)
  */
 static int lan78xx_phy_int_ack(struct lan78xx_net *dev)
 {
-	return lan78xx_write_reg(dev, INT_STS, INT_STS_PHY_INT_);
+		struct phy_device *phydev = dev->net->phydev;
+	int ret = lan78xx_write_reg(dev, INT_STS, INT_STS_PHY_INT_);
+
+	if (unlikely(ret < 0))
+		return ret;
+
+	/* Acknowledge any pending PHY interrupt, lest it be the last */
+	phy_read(phydev, LAN88XX_INT_STS);
+
+	return 0;
 }
 
 /* some work can't be done in tasklets, so we use keventd