PCI: Stop unhiding the SMBus on Toshiba laptops

It was found that the Toshiba laptops with hidden Intel SMBus have SMM
code handling the thermal management which accesses the SMBus. Thus it
is not safe to unhide it and let Linux access it. We have to leave the
SMBus hidden. SMM is a pain, really.

This fixes bugs #6315 and #6395, for good this time.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/pci/quirks.c

@@ -963,6 +963,13 @@ DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_VIA, PCI_DEVICE_ID_VIA_8237, k8t_sound_ho
  * bridge. Unfortunately, this device has no subvendor/subdevice ID. So it 
  * becomes necessary to do this tweak in two steps -- I've chosen the Host
  * bridge as trigger.
+ *
+ * Note that we used to unhide the SMBus that way on Toshiba laptops
+ * (Satellite A40 and Tecra M2) but then found that the thermal management
+ * was done by SMM code, which could cause unsynchronized concurrent
+ * accesses to the SMBus registers, with potentially bad effects. Thus you
+ * should be very careful when adding new entries: if SMM is accessing the
+ * Intel SMBus, this is a very good reason to leave it hidden.
  */
 static int asus_hides_smbus;
 
@@ -1040,17 +1047,6 @@ static void __init asus_hides_smbus_hostbridge(struct pci_dev *dev)
 			case 0x099c: /* HP Compaq nx6110 */
 				asus_hides_smbus = 1;
 			}
-	} else if (unlikely(dev->subsystem_vendor == PCI_VENDOR_ID_TOSHIBA)) {
-		if (dev->device == PCI_DEVICE_ID_INTEL_82855GM_HB)
-			switch(dev->subsystem_device) {
-			case 0x0001: /* Toshiba Satellite A40 */
-				asus_hides_smbus = 1;
-			}
-		else if (dev->device == PCI_DEVICE_ID_INTEL_82855PM_HB)
-			switch(dev->subsystem_device) {
-			case 0x0001: /* Toshiba Tecra M2 */
-				asus_hides_smbus = 1;
-			}
        } else if (unlikely(dev->subsystem_vendor == PCI_VENDOR_ID_SAMSUNG)) {
                if (dev->device ==  PCI_DEVICE_ID_INTEL_82855PM_HB)
                        switch(dev->subsystem_device) {