i2c-i801: Restore the device state before leaving

Restore the original host configuration on driver unload and on
suspend. In particular this returns the SMBus master in I2C mode if it
was originally in I2C mode, which should help with suspend/resume if
the BIOS expects to find the SMBus master in I2C mode.

This fixes bug #6449 (for real this time.)
http://bugzilla.kernel.org/show_bug.cgi?id=6449

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Tommi Kyntola <tommi.kyntola@ray.fi>

drivers/i2c/busses/i2c-i801.c

@@ -97,6 +97,7 @@ static int i801_block_transaction(union i2c_smbus_data *data, char read_write,
 				  int command, int hwpec);
 
 static unsigned long i801_smba;
+static unsigned char i801_original_hstcfg;
 static struct pci_driver i801_driver;
 static struct pci_dev *I801_dev;
 static int isich4;
@@ -510,6 +511,7 @@ static int __devinit i801_probe(struct pci_dev *dev, const struct pci_device_id
 	}
 
 	pci_read_config_byte(I801_dev, SMBHSTCFG, &temp);
+	i801_original_hstcfg = temp;
 	temp &= ~SMBHSTCFG_I2C_EN;	/* SMBus timing */
 	if (!(temp & SMBHSTCFG_HST_EN)) {
 		dev_info(&dev->dev, "Enabling SMBus device\n");
@@ -543,6 +545,7 @@ exit:
 static void __devexit i801_remove(struct pci_dev *dev)
 {
 	i2c_del_adapter(&i801_adapter);
+	pci_write_config_byte(I801_dev, SMBHSTCFG, i801_original_hstcfg);
 	pci_release_region(dev, SMBBAR);
 	/*
 	 * do not call pci_disable_device(dev) since it can cause hard hangs on
@@ -550,11 +553,33 @@ static void __devexit i801_remove(struct pci_dev *dev)
 	 */
 }
 
+#ifdef CONFIG_PM
+static int i801_suspend(struct pci_dev *dev, pm_message_t mesg)
+{
+	pci_save_state(dev);
+	pci_write_config_byte(dev, SMBHSTCFG, i801_original_hstcfg);
+	pci_set_power_state(dev, pci_choose_state(dev, mesg));
+	return 0;
+}
+
+static int i801_resume(struct pci_dev *dev)
+{
+	pci_set_power_state(dev, PCI_D0);
+	pci_restore_state(dev);
+	return pci_enable_device(dev);
+}
+#else
+#define i801_suspend NULL
+#define i801_resume NULL
+#endif
+
 static struct pci_driver i801_driver = {
 	.name		= "i801_smbus",
 	.id_table	= i801_ids,
 	.probe		= i801_probe,
 	.remove		= __devexit_p(i801_remove),
+	.suspend	= i801_suspend,
+	.resume		= i801_resume,
 };
 
 static int __init i2c_i801_init(void)