net: phy: at803x: add qca8081 fifo reset on the link changed

The qca8081 sgmii fifo needs to be reset on link down and
released on the link up in case of any abnormal issue
such as the packet blocked on the PHY.
Signed-off-by: Luo Jie <quic_luoj@quicinc.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/at803x.c

@@ -276,6 +276,9 @@
 #define QCA808X_PHY_MMD7_CHIP_TYPE		0x901d
 #define QCA808X_PHY_CHIP_TYPE_1G		BIT(0)
 
+#define QCA8081_PHY_SERDES_MMD1_FIFO_CTRL	0x9072
+#define QCA8081_PHY_FIFO_RSTN			BIT(11)
+
 MODULE_DESCRIPTION("Qualcomm Atheros AR803x and QCA808X PHY driver");
 MODULE_AUTHOR("Matus Ujhelyi");
 MODULE_LICENSE("GPL");
@@ -2032,6 +2035,16 @@ static int qca808x_get_features(struct phy_device *phydev)
 	return 0;
 }
 
+static void qca808x_link_change_notify(struct phy_device *phydev)
+{
+	/* Assert interface sgmii fifo on link down, deassert it on link up,
+	 * the interface device address is always phy address added by 1.
+	 */
+	mdiobus_c45_modify_changed(phydev->mdio.bus, phydev->mdio.addr + 1,
+			MDIO_MMD_PMAPMD, QCA8081_PHY_SERDES_MMD1_FIFO_CTRL,
+			QCA8081_PHY_FIFO_RSTN, phydev->link ? QCA8081_PHY_FIFO_RSTN : 0);
+}
+
 static struct phy_driver at803x_driver[] = {
 {
 	/* Qualcomm Atheros AR8035 */
@@ -2210,6 +2223,7 @@ static struct phy_driver at803x_driver[] = {
 	.soft_reset		= qca808x_soft_reset,
 	.cable_test_start	= qca808x_cable_test_start,
 	.cable_test_get_status	= qca808x_cable_test_get_status,
+	.link_change_notify	= qca808x_link_change_notify,
 }, };
 
 module_phy_driver(at803x_driver);