gpiolib: Implement set_debounce for WM831x GPIOs

The debounce times are approximate, they can be selected using the two
input functions.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/gpio/wm831x-gpio.c

@@ -108,6 +108,37 @@ static int wm831x_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
 	return wm831x->irq_base + WM831X_IRQ_GPIO_1 + offset;
 }
 
+static int wm831x_gpio_set_debounce(struct gpio_chip *chip, unsigned offset,
+				    unsigned debounce)
+{
+	struct wm831x_gpio *wm831x_gpio = to_wm831x_gpio(chip);
+	struct wm831x *wm831x = wm831x_gpio->wm831x;
+	int reg = WM831X_GPIO1_CONTROL + offset;
+	int ret, fn;
+
+	ret = wm831x_reg_read(wm831x, reg);
+	if (ret < 0)
+		return ret;
+
+	switch (ret & WM831X_GPN_FN_MASK) {
+	case 0:
+	case 1:
+		break;
+	default:
+		/* Not in GPIO mode */
+		return -EBUSY;
+	}
+
+	if (debounce >= 32 && debounce <= 64)
+		fn = 0;
+	else if (debounce >= 4000 && debounce <= 8000)
+		fn = 1;
+	else
+		return -EINVAL;
+
+	return wm831x_set_bits(wm831x, reg, WM831X_GPN_FN_MASK, fn);
+}
+
 #ifdef CONFIG_DEBUG_FS
 static void wm831x_gpio_dbg_show(struct seq_file *s, struct gpio_chip *chip)
 {
@@ -208,6 +239,7 @@ static struct gpio_chip template_chip = {
 	.direction_output	= wm831x_gpio_direction_out,
 	.set			= wm831x_gpio_set,
 	.to_irq			= wm831x_gpio_to_irq,
+	.set_debounce		= wm831x_gpio_set_debounce,
 	.dbg_show		= wm831x_gpio_dbg_show,
 	.can_sleep		= 1,
 };