netdev - [PATCH net-next] net: phy: avoid unneeded MDIO reads in genphy_read

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Message-ID: <92a0d681-33ea-feb7-bdf5-ff6fd9911ce1@gmail.com>
Date:   Wed, 24 Apr 2019 21:49:30 +0200
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        David Miller <davem@...emloft.net>
Cc:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: [PATCH net-next] 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@...il.com>
---
 drivers/net/phy/phy_device.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
index f794ff3a1..2a2aaa5f3 100644
--- 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;
-- 
2.21.0