net: phy: lan87xx: Decrease phy polling rate

Polling at 100Hz for 1.5s consumes quite a bit of kworker time with no
obvious benefit. Reduce that polling rate to ~6Hz.

To further save CPU and power, defer the next poll if no energy is
detected.

See: https://github.com/raspberrypi/linux/issues/4780

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

diff --git a/drivers/net/phy/smsc.c b/drivers/net/phy/smsc.c
index c168a7f..92fa774 100644 (file)
--- a/drivers/net/phy/smsc.c
+++ b/drivers/net/phy/smsc.c
@@ -218,6 +218,8 @@ static int lan87xx_read_status(struct phy_device *phydev)
        int err = genphy_read_status(phydev);
 
        if (!phydev->link && priv->energy_enable) {
+               int energy_detected;
+
                /* Disable EDPD to wake up PHY */
                int rc = phy_read(phydev, MII_LAN83C185_CTRL_STATUS);
                if (rc < 0)
@@ -233,7 +235,7 @@ static int lan87xx_read_status(struct phy_device *phydev)
                 */
                read_poll_timeout(phy_read, rc,
                                  rc & MII_LAN83C185_ENERGYON || rc < 0,
-                                 10000, 1500000, true, phydev,
+                                 150000, 1500000, true, phydev,
                                  MII_LAN83C185_CTRL_STATUS);
                if (rc < 0)
                        return rc;
@@ -243,10 +245,16 @@ static int lan87xx_read_status(struct phy_device *phydev)
                if (rc < 0)
                        return rc;
 
+               energy_detected = !!(rc & MII_LAN83C185_ENERGYON);
+
                rc = phy_write(phydev, MII_LAN83C185_CTRL_STATUS,
                               rc | MII_LAN83C185_EDPWRDOWN);
                if (rc < 0)
                        return rc;
+
+               /* Save CPU and power by deferring the next poll */
+               if (!energy_detected)
+                       msleep(2000);
        }
 
        return err;