watchdog: sp5100_tco: properly check for new register layouts

Commits 190aa4304de6 (Add AMD Mullins platform support) and
cca118fa2a0a94 (Add AMD Carrizo platform support) enabled the
driver on a lot more devices, but the following commit missed
a single location in the code when checking if the SB800 register
offsets should be used. This leads to the wrong register being
written which in turn causes ACPI to go haywire.

Fix this by introducing a helper function to check for the new
register layout and use this consistently.

https://bugzilla.kernel.org/show_bug.cgi?id=114201
https://bugzilla.redhat.com/show_bug.cgi?id=1329910
Fixes: bdecfcdb5461 (sp5100_tco: fix the device check for SB800
and later chipsets)
Cc: stable@vger.kernel.org (4.5+)
Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>

drivers/watchdog/sp5100_tco.c

@@ -73,6 +73,13 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started."
 /*
  * Some TCO specific functions
  */
+
+static bool tco_has_sp5100_reg_layout(struct pci_dev *dev)
+{
+	return dev->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
+	       dev->revision < 0x40;
+}
+
 static void tco_timer_start(void)
 {
 	u32 val;
@@ -129,7 +136,7 @@ static void tco_timer_enable(void)
 {
 	int val;
 
-	if (sp5100_tco_pci->revision >= 0x40) {
+	if (!tco_has_sp5100_reg_layout(sp5100_tco_pci)) {
 		/* For SB800 or later */
 		/* Set the Watchdog timer resolution to 1 sec */
 		outb(SB800_PM_WATCHDOG_CONFIG, SB800_IO_PM_INDEX_REG);
@@ -342,8 +349,7 @@ static unsigned char sp5100_tco_setupdevice(void)
 	/*
 	 * Determine type of southbridge chipset.
 	 */
-	if (sp5100_tco_pci->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
-	    sp5100_tco_pci->revision < 0x40) {
+	if (tco_has_sp5100_reg_layout(sp5100_tco_pci)) {
 		dev_name = SP5100_DEVNAME;
 		index_reg = SP5100_IO_PM_INDEX_REG;
 		data_reg = SP5100_IO_PM_DATA_REG;
@@ -388,8 +394,7 @@ static unsigned char sp5100_tco_setupdevice(void)
 	 * Secondly, Find the watchdog timer MMIO address
 	 * from SBResource_MMIO register.
 	 */
-	if (sp5100_tco_pci->device == PCI_DEVICE_ID_ATI_SBX00_SMBUS &&
-	    sp5100_tco_pci->revision < 0x40) {
+	if (tco_has_sp5100_reg_layout(sp5100_tco_pci)) {
 		/* Read SBResource_MMIO from PCI config(PCI_Reg: 9Ch) */
 		pci_read_config_dword(sp5100_tco_pci,
 				      SP5100_SB_RESOURCE_MMIO_BASE, &val);