smsc75xx: Add workaround for gigabit link up hardware errata.

BugLink: https://bugs.launchpad.net/bugs/1792377

[ Upstream commit d461e3da ]

In certain conditions, the device may not be able to link in gigabit mode. This software workaround ensures that the device will not enter the failure state.

Fixes: d0cad871 ("SMSC75XX USB 2.0 Gigabit Ethernet Devices")
Signed-off-by: Yuiko Oshino <yuiko.oshino@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/usb/smsc75xx.c

@@ -81,6 +81,9 @@ static bool turbo_mode = true;
 module_param(turbo_mode, bool, 0644);
 MODULE_PARM_DESC(turbo_mode, "Enable multiple frames per Rx transaction");
 
+static int smsc75xx_link_ok_nopm(struct usbnet *dev);
+static int smsc75xx_phy_gig_workaround(struct usbnet *dev);
+
 static int __must_check __smsc75xx_read_reg(struct usbnet *dev, u32 index,
 					    u32 *data, int in_pm)
 {
@@ -840,6 +843,9 @@ static int smsc75xx_phy_initialize(struct usbnet *dev)
 		return -EIO;
 	}
 
+	/* phy workaround for gig link */
+	smsc75xx_phy_gig_workaround(dev);
+
 	smsc75xx_mdio_write(dev->net, dev->mii.phy_id, MII_ADVERTISE,
 		ADVERTISE_ALL | ADVERTISE_CSMA | ADVERTISE_PAUSE_CAP |
 		ADVERTISE_PAUSE_ASYM);
@@ -978,6 +984,62 @@ static int smsc75xx_wait_ready(struct usbnet *dev, int in_pm)
 	return -EIO;
 }
 
+static int smsc75xx_phy_gig_workaround(struct usbnet *dev)
+{
+	struct mii_if_info *mii = &dev->mii;
+	int ret = 0, timeout = 0;
+	u32 buf, link_up = 0;
+
+	/* Set the phy in Gig loopback */
+	smsc75xx_mdio_write(dev->net, mii->phy_id, MII_BMCR, 0x4040);
+
+	/* Wait for the link up */
+	do {
+		link_up = smsc75xx_link_ok_nopm(dev);
+		usleep_range(10000, 20000);
+		timeout++;
+	} while ((!link_up) && (timeout < 1000));
+
+	if (timeout >= 1000) {
+		netdev_warn(dev->net, "Timeout waiting for PHY link up\n");
+		return -EIO;
+	}
+
+	/* phy reset */
+	ret = smsc75xx_read_reg(dev, PMT_CTL, &buf);
+	if (ret < 0) {
+		netdev_warn(dev->net, "Failed to read PMT_CTL: %d\n", ret);
+		return ret;
+	}
+
+	buf |= PMT_CTL_PHY_RST;
+
+	ret = smsc75xx_write_reg(dev, PMT_CTL, buf);
+	if (ret < 0) {
+		netdev_warn(dev->net, "Failed to write PMT_CTL: %d\n", ret);
+		return ret;
+	}
+
+	timeout = 0;
+	do {
+		usleep_range(10000, 20000);
+		ret = smsc75xx_read_reg(dev, PMT_CTL, &buf);
+		if (ret < 0) {
+			netdev_warn(dev->net, "Failed to read PMT_CTL: %d\n",
+				    ret);
+			return ret;
+		}
+		timeout++;
+	} while ((buf & PMT_CTL_PHY_RST) && (timeout < 100));
+
+	if (timeout >= 100) {
+		netdev_warn(dev->net, "timeout waiting for PHY Reset\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
 static int smsc75xx_reset(struct usbnet *dev)
 {
 	struct smsc75xx_priv *pdata = (struct smsc75xx_priv *)(dev->data[0]);