net: phy: avoid unneeded MDIO reads in genphy_read_status

Considering that in polling mode each link drop will be latched,
settings can't have changed if link was up and is up.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index f794ff3..2a2aaa5 100644 (file)
--- a/drivers/net/phy/phy_device.c
+++ b/drivers/net/phy/phy_device.c
@@ -1739,13 +1739,17 @@ EXPORT_SYMBOL(genphy_update_link);
  */
 int genphy_read_status(struct phy_device *phydev)
 {
-       int adv, lpa, lpagb, err;
+       int adv, lpa, lpagb, err, old_link = phydev->link;
 
        /* Update the link, but return if there was an error */
        err = genphy_update_link(phydev);
        if (err)
                return err;
 
+       /* why bother the PHY if nothing can have changed */
+       if (phydev->autoneg == AUTONEG_ENABLE && old_link && phydev->link)
+               return 0;
+
        phydev->speed = SPEED_UNKNOWN;
        phydev->duplex = DUPLEX_UNKNOWN;
        phydev->pause = 0;