ARM: imx: Add wake functionality to GPIO

Add function definition for irq_chip.set_wake to enable GPIO to
wake-up the system.

This patch has been tested on a MX51 Babbage system that had suspend
code implemented. The set_wake implementation is necessary for a
GPIO to wake up a system from suspend.
Signed-off-by: Dinh Nguyen <Dinh.Nguyen@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/plat-mxc/gpio.c

@@ -20,6 +20,7 @@
  */
 
 #include <linux/init.h>
+#include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/irq.h>
 #include <linux/gpio.h>
@@ -201,11 +202,42 @@ static void mx2_gpio_irq_handler(u32 irq, struct irq_desc *desc)
 	}
 }
 
+/*
+ * Set interrupt number "irq" in the GPIO as a wake-up source.
+ * While system is running, all registered GPIO interrupts need to have
+ * wake-up enabled. When system is suspended, only selected GPIO interrupts
+ * need to have wake-up enabled.
+ * @param  irq          interrupt source number
+ * @param  enable       enable as wake-up if equal to non-zero
+ * @return       This function returns 0 on success.
+ */
+static int gpio_set_wake_irq(u32 irq, u32 enable)
+{
+	u32 gpio = irq_to_gpio(irq);
+	u32 gpio_idx = gpio & 0x1F;
+	struct mxc_gpio_port *port = &mxc_gpio_ports[gpio / 32];
+
+	if (enable) {
+		if (port->irq_high && (gpio_idx >= 16))
+			enable_irq_wake(port->irq_high);
+		else
+			enable_irq_wake(port->irq);
+	} else {
+		if (port->irq_high && (gpio_idx >= 16))
+			disable_irq_wake(port->irq_high);
+		else
+			disable_irq_wake(port->irq);
+	}
+
+	return 0;
+}
+
 static struct irq_chip gpio_irq_chip = {
 	.ack = gpio_ack_irq,
 	.mask = gpio_mask_irq,
 	.unmask = gpio_unmask_irq,
 	.set_type = gpio_set_irq_type,
+	.set_wake = gpio_set_wake_irq,
 };
 
 static void _set_gpio_direction(struct gpio_chip *chip, unsigned offset,