usbnet: add a mutex around phy register access

When working on the mcs7830, I noticed the need for a mutex in its
mdio_read/mdio_write functions. A related problem seems to be present
in the asix driver in the respective functions.

This introduces a mutex in the common usbnet driver and uses it
from the two hardware specific drivers.
Acked-by: David Hollis <dhollis@davehollis.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/net/asix.c

@@ -569,10 +569,12 @@ static int asix_mdio_read(struct net_device *netdev, int phy_id, int loc)
 	struct usbnet *dev = netdev_priv(netdev);
 	u16 res;
 
+	mutex_lock(&dev->phy_mutex);
 	asix_set_sw_mii(dev);
 	asix_read_cmd(dev, AX_CMD_READ_MII_REG, phy_id,
 				(__u16)loc, 2, (u16 *)&res);
 	asix_set_hw_mii(dev);
+	mutex_unlock(&dev->phy_mutex);
 
 	devdbg(dev, "asix_mdio_read() phy_id=0x%02x, loc=0x%02x, returns=0x%04x", phy_id, loc, le16_to_cpu(res & 0xffff));
 
@@ -586,10 +588,12 @@ asix_mdio_write(struct net_device *netdev, int phy_id, int loc, int val)
 	u16 res = cpu_to_le16(val);
 
 	devdbg(dev, "asix_mdio_write() phy_id=0x%02x, loc=0x%02x, val=0x%04x", phy_id, loc, val);
+	mutex_lock(&dev->phy_mutex);
 	asix_set_sw_mii(dev);
 	asix_write_cmd(dev, AX_CMD_WRITE_MII_REG, phy_id,
 				(__u16)loc, 2, (u16 *)&res);
 	asix_set_hw_mii(dev);
+	mutex_unlock(&dev->phy_mutex);
 }
 
 /* Get the PHY Identifier from the PHYSID1 & PHYSID2 MII registers */

drivers/usb/net/mcs7830.c

@@ -184,6 +184,7 @@ static int mcs7830_read_phy(struct usbnet *dev, u8 index)
 		HIF_REG_PHY_CMD2_PEND_FLAG_BIT | index,
 	};
 
+	mutex_lock(&dev->phy_mutex);
 	/* write the MII command */
 	ret = mcs7830_set_reg(dev, HIF_REG_PHY_CMD1, 2, cmd);
 	if (ret < 0)
@@ -208,6 +209,7 @@ static int mcs7830_read_phy(struct usbnet *dev, u8 index)
 	dev_dbg(&dev->udev->dev, "read PHY reg %02x: %04x (%d tries)\n",
 		index, val, i);
 out:
+	mutex_unlock(&dev->phy_mutex);
 	return ret;
 }
 
@@ -222,6 +224,8 @@ static int mcs7830_write_phy(struct usbnet *dev, u8 index, u16 val)
 		HIF_REG_PHY_CMD2_PEND_FLAG_BIT | (index & 0x1F),
 	};
 
+	mutex_lock(&dev->phy_mutex);
+
 	/* write the new register contents */
 	le_val = cpu_to_le16(val);
 	ret = mcs7830_set_reg(dev, HIF_REG_PHY_DATA, 2, &le_val);
@@ -248,6 +252,7 @@ static int mcs7830_write_phy(struct usbnet *dev, u8 index, u16 val)
 	dev_dbg(&dev->udev->dev, "write PHY reg %02x: %04x (%d tries)\n",
 		index, val, i);
 out:
+	mutex_unlock(&dev->phy_mutex);
 	return ret;
 }
 

drivers/usb/net/usbnet.c

@@ -1144,6 +1144,7 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 	dev->delay.function = usbnet_bh;
 	dev->delay.data = (unsigned long) dev;
 	init_timer (&dev->delay);
+	mutex_init (&dev->phy_mutex);
 
 	SET_MODULE_OWNER (net);
 	dev->net = net;

drivers/usb/net/usbnet.h

@@ -30,6 +30,7 @@ struct usbnet {
 	struct usb_device	*udev;
 	struct driver_info	*driver_info;
 	wait_queue_head_t	*wait;
+	struct mutex		phy_mutex;
 
 	/* i/o info: pipes etc */
 	unsigned		in, out;