diff --git a/drivers/usb/net/asix.c b/drivers/usb/net/asix.c
index 5edd053..881841e 100644
--- a/drivers/usb/net/asix.c
+++ b/drivers/usb/net/asix.c
@@ -569,10 +569,12 @@
 	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 @@
 	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 */
diff --git a/drivers/usb/net/mcs7830.c b/drivers/usb/net/mcs7830.c
index 23a8066..6240b97 100644
--- a/drivers/usb/net/mcs7830.c
+++ b/drivers/usb/net/mcs7830.c
@@ -184,6 +184,7 @@
 		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 @@
 	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 @@
 		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 @@
 	dev_dbg(&dev->udev->dev, "write PHY reg %02x: %04x (%d tries)\n",
 		index, val, i);
 out:
+	mutex_unlock(&dev->phy_mutex);
 	return ret;
 }
 
diff --git a/drivers/usb/net/usbnet.c b/drivers/usb/net/usbnet.c
index decc1b1..cf3d20e 100644
--- a/drivers/usb/net/usbnet.c
+++ b/drivers/usb/net/usbnet.c
@@ -1144,6 +1144,7 @@
 	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;
diff --git a/drivers/usb/net/usbnet.h b/drivers/usb/net/usbnet.h
index 743947c..07c70ab 100644
--- a/drivers/usb/net/usbnet.h
+++ b/drivers/usb/net/usbnet.h
@@ -30,6 +30,7 @@
 	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;