net: phy: smsc: disable energy detect mode

On some boards the energy enable detect mode leads in
trouble with some switches, so make the enabling of
this mode configurable through DT.
Signed-off-by: Heiko Schocher <hs@denx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/smsc-lan87xx.txt

+SMSC LAN87xx Ethernet PHY
+
+Some boards require special tuning values. Configure them
+through an Ethernet OF device node.
+
+Optional properties:
+
+- smsc,disable-energy-detect:
+  If set, do not enable energy detect mode for the SMSC phy.
+  default: enable energy detect mode
+
+Examples:
+smsc phy with disabled energy detect mode on an am335x based board.
+&davinci_mdio {
+	pinctrl-names = "default", "sleep";
+	pinctrl-0 = <&davinci_mdio_default>;
+	pinctrl-1 = <&davinci_mdio_sleep>;
+	status = "okay";
+
+	ethernetphy0: ethernet-phy@0 {
+		reg = <0>;
+		smsc,disable-energy-detect;
+	};
+};

drivers/net/phy/smsc.c

@@ -43,16 +43,25 @@ static int smsc_phy_ack_interrupt(struct phy_device *phydev)
 
 static int smsc_phy_config_init(struct phy_device *phydev)
 {
+	int __maybe_unused len;
+	struct device *dev __maybe_unused = &phydev->dev;
+	struct device_node *of_node __maybe_unused = dev->of_node;
 	int rc = phy_read(phydev, MII_LAN83C185_CTRL_STATUS);
+	int enable_energy = 1;
 
 	if (rc < 0)
 		return rc;
 
-	/* Enable energy detect mode for this SMSC Transceivers */
-	rc = phy_write(phydev, MII_LAN83C185_CTRL_STATUS,
-		       rc | MII_LAN83C185_EDPWRDOWN);
-	if (rc < 0)
-		return rc;
+	if (of_find_property(of_node, "smsc,disable-energy-detect", &len))
+		enable_energy = 0;
+
+	if (enable_energy) {
+		/* Enable energy detect mode for this SMSC Transceivers */
+		rc = phy_write(phydev, MII_LAN83C185_CTRL_STATUS,
+			       rc | MII_LAN83C185_EDPWRDOWN);
+		if (rc < 0)
+			return rc;
+	}
 
 	return smsc_phy_ack_interrupt(phydev);
 }