gpio: langwell: ensure alternate function is cleared

Alternate function must be zero for the pin to act as
a GPIO.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/gpio/gpio-langwell.c

@@ -59,6 +59,7 @@ enum GPIO_REG {
 	GRER,		/* rising edge detect */
 	GFER,		/* falling edge detect */
 	GEDR,		/* edge detect result */
+	GAFR,		/* alt function */
 };
 
 struct lnw_gpio {
@@ -81,6 +82,31 @@ static void __iomem *gpio_reg(struct gpio_chip *chip, unsigned offset,
 	return ptr;
 }
 
+static void __iomem *gpio_reg_2bit(struct gpio_chip *chip, unsigned offset,
+				   enum GPIO_REG reg_type)
+{
+	struct lnw_gpio *lnw = container_of(chip, struct lnw_gpio, chip);
+	unsigned nreg = chip->ngpio / 32;
+	u8 reg = offset / 16;
+	void __iomem *ptr;
+
+	ptr = (void __iomem *)(lnw->reg_base + reg_type * nreg * 4 + reg * 4);
+	return ptr;
+}
+
+static int lnw_gpio_request(struct gpio_chip *chip, unsigned offset)
+{
+	void __iomem *gafr = gpio_reg_2bit(chip, offset, GAFR);
+	u32 value = readl(gafr);
+	int shift = (offset % 16) << 1, af = (value >> shift) & 3;
+
+	if (af) {
+		value &= ~(3 << shift);
+		writel(value, gafr);
+	}
+	return 0;
+}
+
 static int lnw_gpio_get(struct gpio_chip *chip, unsigned offset)
 {
 	void __iomem *gplr = gpio_reg(chip, offset, GPLR);
@@ -321,6 +347,7 @@ static int __devinit lnw_gpio_probe(struct pci_dev *pdev,
 	lnw->reg_base = base;
 	lnw->irq_base = irq_base;
 	lnw->chip.label = dev_name(&pdev->dev);
+	lnw->chip.request = lnw_gpio_request;
 	lnw->chip.direction_input = lnw_gpio_direction_input;
 	lnw->chip.direction_output = lnw_gpio_direction_output;
 	lnw->chip.get = lnw_gpio_get;