net: phy: deal properly with autoneg incomplete in genphy_c45_read_lpa

The link partner advertisement registers are not guaranteed to contain
valid values if autoneg is incomplete. Therefore, if
MDIO_AN_STAT1_COMPLETE isn't set, let's clear all link partner
capability bits. This also avoids unnecessary register reads if link
is down and phylib is in polling mode.
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy-c45.c

@@ -266,6 +266,17 @@ int genphy_c45_read_lpa(struct phy_device *phydev)
 	if (val < 0)
 		return val;
 
+	if (!(val & MDIO_AN_STAT1_COMPLETE)) {
+		linkmode_clear_bit(ETHTOOL_LINK_MODE_Autoneg_BIT,
+				   phydev->lp_advertising);
+		mii_10gbt_stat_mod_linkmode_lpa_t(phydev->lp_advertising, 0);
+		mii_adv_mod_linkmode_adv_t(phydev->lp_advertising, 0);
+		phydev->pause = 0;
+		phydev->asym_pause = 0;
+
+		return 0;
+	}
+
 	linkmode_mod_bit(ETHTOOL_LINK_MODE_Autoneg_BIT, phydev->lp_advertising,
 			 val & MDIO_AN_STAT1_LPABLE);