net: phy: genphy_loopback: add link speed configuration

In case of loopback, in most cases we need to disable autoneg support
and force some speed configuration. Otherwise, depending on currently
active auto negotiated link speed, the loopback may or may not work.

This patch was tested with following PHYs: TJA1102, KSZ8081, KSZ9031,
AT8035, AR9331.

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/phy.c

@@ -701,7 +701,7 @@ int phy_start_cable_test_tdr(struct phy_device *phydev,
 }
 EXPORT_SYMBOL(phy_start_cable_test_tdr);
 
-static int phy_config_aneg(struct phy_device *phydev)
+int phy_config_aneg(struct phy_device *phydev)
 {
 	if (phydev->drv->config_aneg)
 		return phydev->drv->config_aneg(phydev);
@@ -714,6 +714,7 @@ static int phy_config_aneg(struct phy_device *phydev)
 
 	return genphy_config_aneg(phydev);
 }
+EXPORT_SYMBOL(phy_config_aneg);
 
 /**
  * phy_check_link_status - check link status and set state accordingly

drivers/net/phy/phy_device.c

@@ -2565,8 +2565,32 @@ EXPORT_SYMBOL(genphy_resume);
 
 int genphy_loopback(struct phy_device *phydev, bool enable)
 {
-	return phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK,
-			  enable ? BMCR_LOOPBACK : 0);
+	if (enable) {
+		u16 val, ctl = BMCR_LOOPBACK;
+		int ret;
+
+		if (phydev->speed == SPEED_1000)
+			ctl |= BMCR_SPEED1000;
+		else if (phydev->speed == SPEED_100)
+			ctl |= BMCR_SPEED100;
+
+		if (phydev->duplex == DUPLEX_FULL)
+			ctl |= BMCR_FULLDPLX;
+
+		phy_modify(phydev, MII_BMCR, ~0, ctl);
+
+		ret = phy_read_poll_timeout(phydev, MII_BMSR, val,
+					    val & BMSR_LSTATUS,
+				    5000, 500000, true);
+		if (ret)
+			return ret;
+	} else {
+		phy_modify(phydev, MII_BMCR, BMCR_LOOPBACK, 0);
+
+		phy_config_aneg(phydev);
+	}
+
+	return 0;
 }
 EXPORT_SYMBOL(genphy_loopback);
 

include/linux/phy.h

@@ -1410,6 +1410,7 @@ void phy_disconnect(struct phy_device *phydev);
 void phy_detach(struct phy_device *phydev);
 void phy_start(struct phy_device *phydev);
 void phy_stop(struct phy_device *phydev);
+int phy_config_aneg(struct phy_device *phydev);
 int phy_start_aneg(struct phy_device *phydev);
 int phy_aneg_done(struct phy_device *phydev);
 int phy_speed_down(struct phy_device *phydev, bool sync);