smsc95xx: Ignore -ENODEV errors when device is unplugged

According to Documentation/driver-api/usb/URB.rst when a device
is unplugged usb_submit_urb() returns -ENODEV.

This error code propagates all the way up to usbnet_read_cmd() and
usbnet_write_cmd() calls inside the smsc95xx.c driver during
Ethernet cable unplug, unbind or reboot.

This causes the following errors to be shown on reboot, for example:

ci_hdrc ci_hdrc.1: remove, state 1
usb usb2: USB disconnect, device number 1
usb 2-1: USB disconnect, device number 2
usb 2-1.1: USB disconnect, device number 3
smsc95xx 2-1.1:1.0 eth1: unregister 'smsc95xx' usb-ci_hdrc.1-1.1, smsc95xx USB 2.0 Ethernet
smsc95xx 2-1.1:1.0 eth1: Failed to read reg index 0x00000114: -19
smsc95xx 2-1.1:1.0 eth1: Error reading MII_ACCESS
smsc95xx 2-1.1:1.0 eth1: __smsc95xx_mdio_read: MII is busy
smsc95xx 2-1.1:1.0 eth1: Failed to read reg index 0x00000114: -19
smsc95xx 2-1.1:1.0 eth1: Error reading MII_ACCESS
smsc95xx 2-1.1:1.0 eth1: __smsc95xx_mdio_read: MII is busy
smsc95xx 2-1.1:1.0 eth1: hardware isn't capable of remote wakeup
usb 2-1.4: USB disconnect, device number 4
ci_hdrc ci_hdrc.1: USB bus 2 deregistered
ci_hdrc ci_hdrc.0: remove, state 4
usb usb1: USB disconnect, device number 1
ci_hdrc ci_hdrc.0: USB bus 1 deregistered
imx2-wdt 30280000.watchdog: Device shutdown: Expect reboot!
reboot: Restarting system

Ignore the -ENODEV errors inside __smsc95xx_mdio_read() and
__smsc95xx_phy_wait_not_busy() and do not print error messages
when -ENODEV is returned.

Fixes: a049a30f ("net: usb: Correct PHY handling of smsc95xx")
Signed-off-by: Fabio Estevam <festevam@denx.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/usb/smsc95xx.c

@@ -84,7 +84,8 @@ static int __must_check __smsc95xx_read_reg(struct usbnet *dev, u32 index,
 	ret = fn(dev, USB_VENDOR_REQUEST_READ_REGISTER, USB_DIR_IN
 		 | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 		 0, index, &buf, 4);
-	if (unlikely(ret < 0)) {
+	if (ret < 0) {
+		if (ret != -ENODEV)
 			netdev_warn(dev->net, "Failed to read reg index 0x%08x: %d\n",
 				    index, ret);
 		return ret;
@@ -116,7 +117,7 @@ static int __must_check __smsc95xx_write_reg(struct usbnet *dev, u32 index,
 	ret = fn(dev, USB_VENDOR_REQUEST_WRITE_REGISTER, USB_DIR_OUT
 		 | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 		 0, index, &buf, 4);
-	if (unlikely(ret < 0))
+	if (ret < 0 && ret != -ENODEV)
 		netdev_warn(dev->net, "Failed to write reg index 0x%08x: %d\n",
 			    index, ret);
 
@@ -159,6 +160,9 @@ static int __must_check __smsc95xx_phy_wait_not_busy(struct usbnet *dev,
 	do {
 		ret = __smsc95xx_read_reg(dev, MII_ADDR, &val, in_pm);
 		if (ret < 0) {
+			/* Ignore -ENODEV error during disconnect() */
+			if (ret == -ENODEV)
+				return 0;
 			netdev_warn(dev->net, "Error reading MII_ACCESS\n");
 			return ret;
 		}
@@ -194,6 +198,7 @@ static int __smsc95xx_mdio_read(struct usbnet *dev, int phy_id, int idx,
 	addr = mii_address_cmd(phy_id, idx, MII_READ_ | MII_BUSY_);
 	ret = __smsc95xx_write_reg(dev, MII_ADDR, addr, in_pm);
 	if (ret < 0) {
+		if (ret != -ENODEV)
 			netdev_warn(dev->net, "Error writing MII_ADDR\n");
 		goto done;
 	}
@@ -206,6 +211,7 @@ static int __smsc95xx_mdio_read(struct usbnet *dev, int phy_id, int idx,
 
 	ret = __smsc95xx_read_reg(dev, MII_DATA, &val, in_pm);
 	if (ret < 0) {
+		if (ret != -ENODEV)
 			netdev_warn(dev->net, "Error reading MII_DATA\n");
 		goto done;
 	}
@@ -214,6 +220,10 @@ static int __smsc95xx_mdio_read(struct usbnet *dev, int phy_id, int idx,
 
 done:
 	mutex_unlock(&dev->phy_mutex);
+
+	/* Ignore -ENODEV error during disconnect() */
+	if (ret == -ENODEV)
+		return 0;
 	return ret;
 }
 
@@ -235,6 +245,7 @@ static void __smsc95xx_mdio_write(struct usbnet *dev, int phy_id,
 	val = regval;
 	ret = __smsc95xx_write_reg(dev, MII_DATA, val, in_pm);
 	if (ret < 0) {
+		if (ret != -ENODEV)
 			netdev_warn(dev->net, "Error writing MII_DATA\n");
 		goto done;
 	}
@@ -243,6 +254,7 @@ static void __smsc95xx_mdio_write(struct usbnet *dev, int phy_id,
 	addr = mii_address_cmd(phy_id, idx, MII_WRITE_ | MII_BUSY_);
 	ret = __smsc95xx_write_reg(dev, MII_ADDR, addr, in_pm);
 	if (ret < 0) {
+		if (ret != -ENODEV)
 			netdev_warn(dev->net, "Error writing MII_ADDR\n");
 		goto done;
 	}