net: usb: smsc95xx: fix external PHY reset

An external PHY needs settling time after power up or reset.
In the bind() function an mdio bus is registered. If at this point
the external PHY is still initialising, no valid PHY ID will be
read and on phy_find_first() the bind() function will fail.

If an external PHY is present, wait the maximum time specified
in 802.3 45.2.7.1.1.

Fixes: 05b35e7eb9 ("smsc95xx: add phylib support")
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Link: https://lore.kernel.org/r/20221115114434.9991-2-alexandru.tachici@analog.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/usb/smsc95xx.c

@@ -66,6 +66,7 @@ struct smsc95xx_priv {
 	spinlock_t mac_cr_lock;
 	u8 features;
 	u8 suspend_flags;
+	bool is_internal_phy;
 	struct irq_chip irqchip;
 	struct irq_domain *irqdomain;
 	struct fwnode_handle *irqfwnode;
@@ -252,6 +253,43 @@ done:
 	mutex_unlock(&dev->phy_mutex);
 }
 
+static int smsc95xx_mdiobus_reset(struct mii_bus *bus)
+{
+	struct smsc95xx_priv *pdata;
+	struct usbnet *dev;
+	u32 val;
+	int ret;
+
+	dev = bus->priv;
+	pdata = dev->driver_priv;
+
+	if (pdata->is_internal_phy)
+		return 0;
+
+	mutex_lock(&dev->phy_mutex);
+
+	ret = smsc95xx_read_reg(dev, PM_CTRL, &val);
+	if (ret < 0)
+		goto reset_out;
+
+	val |= PM_CTL_PHY_RST_;
+
+	ret = smsc95xx_write_reg(dev, PM_CTRL, val);
+	if (ret < 0)
+		goto reset_out;
+
+	/* Driver has no knowledge at this point about the external PHY.
+	 * The 802.3 specifies that the reset process shall
+	 * be completed within 0.5 s.
+	 */
+	fsleep(500000);
+
+reset_out:
+	mutex_unlock(&dev->phy_mutex);
+
+	return 0;
+}
+
 static int smsc95xx_mdiobus_read(struct mii_bus *bus, int phy_id, int idx)
 {
 	struct usbnet *dev = bus->priv;
@@ -1052,7 +1090,6 @@ static void smsc95xx_handle_link_change(struct net_device *net)
 static int smsc95xx_bind(struct usbnet *dev, struct usb_interface *intf)
 {
 	struct smsc95xx_priv *pdata;
-	bool is_internal_phy;
 	char usb_path[64];
 	int ret, phy_irq;
 	u32 val;
@@ -1133,13 +1170,14 @@ static int smsc95xx_bind(struct usbnet *dev, struct usb_interface *intf)
 	if (ret < 0)
 		goto free_mdio;
 
-	is_internal_phy = !(val & HW_CFG_PSEL_);
-	if (is_internal_phy)
+	pdata->is_internal_phy = !(val & HW_CFG_PSEL_);
+	if (pdata->is_internal_phy)
 		pdata->mdiobus->phy_mask = ~(1u << SMSC95XX_INTERNAL_PHY_ID);
 
 	pdata->mdiobus->priv = dev;
 	pdata->mdiobus->read = smsc95xx_mdiobus_read;
 	pdata->mdiobus->write = smsc95xx_mdiobus_write;
+	pdata->mdiobus->reset = smsc95xx_mdiobus_reset;
 	pdata->mdiobus->name = "smsc95xx-mdiobus";
 	pdata->mdiobus->parent = &dev->udev->dev;
 
@@ -1160,7 +1198,7 @@ static int smsc95xx_bind(struct usbnet *dev, struct usb_interface *intf)
 	}
 
 	pdata->phydev->irq = phy_irq;
-	pdata->phydev->is_internal = is_internal_phy;
+	pdata->phydev->is_internal = pdata->is_internal_phy;
 
 	/* detect device revision as different features may be available */
 	ret = smsc95xx_read_reg(dev, ID_REV, &val);