diff --git a/drivers/i2c/busses/i2c-piix4.c b/drivers/i2c/busses/i2c-piix4.c
index c21ca7b..8f1c5f2 100644
--- a/drivers/i2c/busses/i2c-piix4.c
+++ b/drivers/i2c/busses/i2c-piix4.c
@@ -94,6 +94,12 @@
 #define SB800_PIIX4_PORT_IDX_ALT	0x2e
 #define SB800_PIIX4_PORT_IDX_SEL	0x2f
 #define SB800_PIIX4_PORT_IDX_MASK	0x06
+#define SB800_PIIX4_PORT_IDX_SHIFT	1
+
+/* On kerncz, SmBus0Sel is at bit 20:19 of PMx00 DecodeEn */
+#define SB800_PIIX4_PORT_IDX_KERNCZ		0x02
+#define SB800_PIIX4_PORT_IDX_MASK_KERNCZ	0x18
+#define SB800_PIIX4_PORT_IDX_SHIFT_KERNCZ	3
 
 /* insmod parameters */
 
@@ -149,6 +155,8 @@
  */
 static DEFINE_MUTEX(piix4_mutex_sb800);
 static u8 piix4_port_sel_sb800;
+static u8 piix4_port_mask_sb800;
+static u8 piix4_port_shift_sb800;
 static const char *piix4_main_port_names_sb800[PIIX4_MAX_ADAPTERS] = {
 	" port 0", " port 2", " port 3", " port 4"
 };
@@ -347,7 +355,19 @@
 
 	/* Find which register is used for port selection */
 	if (PIIX4_dev->vendor == PCI_VENDOR_ID_AMD) {
-		piix4_port_sel_sb800 = SB800_PIIX4_PORT_IDX_ALT;
+		switch (PIIX4_dev->device) {
+		case PCI_DEVICE_ID_AMD_KERNCZ_SMBUS:
+			piix4_port_sel_sb800 = SB800_PIIX4_PORT_IDX_KERNCZ;
+			piix4_port_mask_sb800 = SB800_PIIX4_PORT_IDX_MASK_KERNCZ;
+			piix4_port_shift_sb800 = SB800_PIIX4_PORT_IDX_SHIFT_KERNCZ;
+			break;
+		case PCI_DEVICE_ID_AMD_HUDSON2_SMBUS:
+		default:
+			piix4_port_sel_sb800 = SB800_PIIX4_PORT_IDX_ALT;
+			piix4_port_mask_sb800 = SB800_PIIX4_PORT_IDX_MASK;
+			piix4_port_shift_sb800 = SB800_PIIX4_PORT_IDX_SHIFT;
+			break;
+		}
 	} else {
 		mutex_lock(&piix4_mutex_sb800);
 		outb_p(SB800_PIIX4_PORT_IDX_SEL, SB800_PIIX4_SMB_IDX);
@@ -355,6 +375,8 @@
 		piix4_port_sel_sb800 = (port_sel & 0x01) ?
 				       SB800_PIIX4_PORT_IDX_ALT :
 				       SB800_PIIX4_PORT_IDX;
+		piix4_port_mask_sb800 = SB800_PIIX4_PORT_IDX_MASK;
+		piix4_port_shift_sb800 = SB800_PIIX4_PORT_IDX_SHIFT;
 		mutex_unlock(&piix4_mutex_sb800);
 	}
 
@@ -616,8 +638,8 @@
 	smba_en_lo = inb_p(SB800_PIIX4_SMB_IDX + 1);
 
 	port = adapdata->port;
-	if ((smba_en_lo & SB800_PIIX4_PORT_IDX_MASK) != port)
-		outb_p((smba_en_lo & ~SB800_PIIX4_PORT_IDX_MASK) | port,
+	if ((smba_en_lo & piix4_port_mask_sb800) != port)
+		outb_p((smba_en_lo & ~piix4_port_mask_sb800) | port,
 		       SB800_PIIX4_SMB_IDX + 1);
 
 	retval = piix4_access(adap, addr, flags, read_write,
@@ -706,7 +728,7 @@
 
 	adapdata->smba = smba;
 	adapdata->sb800_main = sb800_main;
-	adapdata->port = port << 1;
+	adapdata->port = port << piix4_port_shift_sb800;
 
 	/* set up the sysfs linkage to our parent device */
 	adap->dev.parent = &dev->dev;