i2c: piix4: Fix probing of reserved ports on AMD Family 16h Model 30h

Prevent bus timeouts and resets on Family 16h Model 30h by not probing
reserved Ports 3 and 4.

According to the AMD BIOS and Kernel Developer's Guides (BKDG), Port 3
and Port 4 are reserved on the following devices:
- Family 15h Model 60h-6Fh
- Family 15h Model 70h-7Fh
- Family 16h Model 30h-3Fh

Based on earlier work by Andrew Cooks.

Reported-by: Andrew Cooks <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>
Signed-off-by: Wolfram Sang <[e-mail]>

drivers/i2c/busses/i2c-piix4.c

···
 #define PIIX4_BLOCK_DATA	0x14
 
 /* Multi-port constants */
-#define PIIX4_MAX_ADAPTERS 4
+#define PIIX4_MAX_ADAPTERS	4
+#define HUDSON2_MAIN_PORTS	2 /* HUDSON2, KERNCZ reserves ports 3, 4 */
 
 /* SB800 constants */
 #define SB800_PIIX4_SMB_IDX		0xcd6
···
 
 static struct i2c_adapter *piix4_main_adapters[PIIX4_MAX_ADAPTERS];
 static struct i2c_adapter *piix4_aux_adapter;
+static int piix4_adapter_count;
 
 static int piix4_add_adapter(struct pci_dev *dev, unsigned short smba,
 			     bool sb800_main, u8 port, bool notify_imc,
···
 	int port;
 	int retval;
 
-	for (port = 0; port < PIIX4_MAX_ADAPTERS; port++) {
+	if (dev->device == PCI_DEVICE_ID_AMD_KERNCZ_SMBUS ||
+	    (dev->device == PCI_DEVICE_ID_AMD_HUDSON2_SMBUS &&
+	     dev->revision >= 0x1F)) {
+		piix4_adapter_count = HUDSON2_MAIN_PORTS;
+	} else {
+		piix4_adapter_count = PIIX4_MAX_ADAPTERS;
+	}
+
+	for (port = 0; port < piix4_adapter_count; port++) {
 		retval = piix4_add_adapter(dev, smba, true, port, notify_imc,
 					   piix4_main_port_names_sb800[port],
 					   &piix4_main_adapters[port]);
···
 
 static void piix4_remove(struct pci_dev *dev)
 {
-	int port = PIIX4_MAX_ADAPTERS;
+	int port = piix4_adapter_count;
 
 	while (--port >= 0) {
 		if (piix4_main_adapters[port]) {