i2c: i801: store and restore the SLVCMD register at load and unload

commit 22e94bd6 upstream.

Also do not override any other configuration in this register.
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Cc: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/i2c/busses/i2c-i801.c

@@ -243,6 +243,7 @@ struct i801_priv {
 	struct i2c_adapter adapter;
 	unsigned long smba;
 	unsigned char original_hstcfg;
+	unsigned char original_slvcmd;
 	struct pci_dev *pci_dev;
 	unsigned int features;
 
@@ -962,13 +963,26 @@ static int i801_enable_host_notify(struct i2c_adapter *adapter)
 	if (!priv->host_notify)
 		return -ENOMEM;
 
-	outb_p(SMBSLVCMD_HST_NTFY_INTREN, SMBSLVCMD(priv));
+	priv->original_slvcmd = inb_p(SMBSLVCMD(priv));
+
+	if (!(SMBSLVCMD_HST_NTFY_INTREN & priv->original_slvcmd))
+		outb_p(SMBSLVCMD_HST_NTFY_INTREN | priv->original_slvcmd,
+		       SMBSLVCMD(priv));
+
 	/* clear Host Notify bit to allow a new notification */
 	outb_p(SMBSLVSTS_HST_NTFY_STS, SMBSLVSTS(priv));
 
 	return 0;
 }
 
+static void i801_disable_host_notify(struct i801_priv *priv)
+{
+	if (!(priv->features & FEATURE_HOST_NOTIFY))
+		return;
+
+	outb_p(priv->original_slvcmd, SMBSLVCMD(priv));
+}
+
 static const struct i2c_algorithm smbus_algorithm = {
 	.smbus_xfer	= i801_access,
 	.functionality	= i801_func,
@@ -1666,6 +1680,7 @@ static void i801_remove(struct pci_dev *dev)
 	pm_runtime_forbid(&dev->dev);
 	pm_runtime_get_noresume(&dev->dev);
 
+	i801_disable_host_notify(priv);
 	i801_del_mux(priv);
 	i2c_del_adapter(&priv->adapter);
 	i801_acpi_remove(priv);