diff --git a/drivers/mfd/sm501.c b/drivers/mfd/sm501.c
index be87139..c3e5a48 100644
--- a/drivers/mfd/sm501.c
+++ b/drivers/mfd/sm501.c
@@ -996,12 +996,13 @@
 {
 	struct sm501_platdata *pdata = sm->platdata;
 	struct gpio_chip *gchip = &chip->gpio;
-	unsigned base = pdata->gpio_base;
+	int base = pdata->gpio_base;
 
 	memcpy(chip, &gpio_chip_template, sizeof(struct gpio_chip));
 
 	if (chip == &gpio->high) {
-		base += 32;
+		if (base > 0)
+			base += 32;
 		chip->regbase = gpio->regs + SM501_GPIO_DATA_HIGH;
 		gchip->label  = "SM501-HIGH";
 	} else {
@@ -1452,6 +1453,7 @@
 static struct sm501_platdata sm501_pci_platdata = {
 	.init		= &sm501_pci_initdata,
 	.fb		= &sm501_fb_pdata,
+	.gpio_base	= -1,
 };
 
 static int sm501_pci_probe(struct pci_dev *dev,
diff --git a/include/linux/sm501.h b/include/linux/sm501.h
index 6ea3900..a8d02f3 100644
--- a/include/linux/sm501.h
+++ b/include/linux/sm501.h
@@ -156,7 +156,7 @@
 	struct sm501_platdata_fb	*fb;
 
 	int				 flags;
-	unsigned			 gpio_base;
+	int				 gpio_base;
 
 	int	(*get_power)(struct device *dev);
 	int	(*set_power)(struct device *dev, unsigned int on);