net: phy: mscc: coma mode disabled for VSC8514

The 'coma mode' (configurable through sw or hw) provides an
optional feature that may be used to control when the PHYs become active.
The typical usage is to synchronize the link-up time across
all PHY instances. This patch releases coma mode if not done by hardware,
otherwise the phys will not link-up.

Fixes: e4f9ba6 ("net: phy: mscc: add support for VSC8514 PHY.")
Signed-off-by: Steen Hegelund <steen.hegelund@microchip.com>
Signed-off-by: Bjarni Jonasson <bjarni.jonasson@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/mscc/mscc.h

@@ -140,6 +140,10 @@ enum rgmii_clock_delay {
 #define MSCC_PHY_PAGE_1588		  0x1588 /* PTP (1588) */
 #define MSCC_PHY_PAGE_TEST		  0x2a30 /* Test reg */
 #define MSCC_PHY_PAGE_TR		  0x52b5 /* Token ring registers */
+#define MSCC_PHY_GPIO_CONTROL_2           14
+
+#define MSCC_PHY_COMA_MODE		  0x2000 /* input(1) / output(0) */
+#define MSCC_PHY_COMA_OUTPUT		  0x1000 /* value to output */
 
 /* Extended Page 1 Registers */
 #define MSCC_PHY_CU_MEDIA_CRC_VALID_CNT	  18

drivers/net/phy/mscc/mscc_main.c

@@ -1516,6 +1516,21 @@ static void vsc8584_get_base_addr(struct phy_device *phydev)
 	vsc8531->addr = addr;
 }
 
+static void vsc85xx_coma_mode_release(struct phy_device *phydev)
+{
+	/* The coma mode (pin or reg) provides an optional feature that
+	 * may be used to control when the PHYs become active.
+	 * Alternatively the COMA_MODE pin may be connected low
+	 * so that the PHYs are fully active once out of reset.
+	 */
+
+	/* Enable output (mode=0) and write zero to it */
+	vsc85xx_phy_write_page(phydev, MSCC_PHY_PAGE_EXTENDED_GPIO);
+	__phy_modify(phydev, MSCC_PHY_GPIO_CONTROL_2,
+		     MSCC_PHY_COMA_MODE | MSCC_PHY_COMA_OUTPUT, 0);
+	vsc85xx_phy_write_page(phydev, MSCC_PHY_PAGE_STANDARD);
+}
+
 static int vsc8584_config_init(struct phy_device *phydev)
 {
 	struct vsc8531_private *vsc8531 = phydev->priv;
@@ -1962,6 +1977,7 @@ static int vsc8514_config_init(struct phy_device *phydev)
 		ret = vsc8514_config_host_serdes(phydev);
 		if (ret)
 			goto err;
+		vsc85xx_coma_mode_release(phydev);
 	}
 
 	phy_unlock_mdio_bus(phydev);