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>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/usb/net/asix.c b/drivers/usb/net/asix.c
index 5edd0534c7ab..881841e600de 100644
--- a/drivers/usb/net/asix.c
+++ b/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 */