[RFC PATCH v3 6/7] gpiolib: enable GPIO interrupt to wake up a system from sleep

[Alex Soo <yuklin.soo@xxxxxxxxxxxxxxxx>]

Add function gpiochip_wakeup_irq_setup() to configure and enable a
GPIO pin with interrupt wakeup capability according to user-defined
wakeup-gpios property in the device tree. Interrupt generated by
toggling the logic level (rising/falling edge) on the specified
GPIO pin can wake up a system from sleep mode.

Signed-off-by: Alex Soo <yuklin.soo@xxxxxxxxxxxxxxxx>
---
 drivers/gpio/gpiolib.c | 87 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 94903fc1c145..92cfbc34abb0 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -19,6 +19,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/pinctrl/consumer.h>
+#include <linux/pm_wakeirq.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
@@ -96,6 +97,7 @@ static void gpiochip_irqchip_remove(struct gpio_chip *gc);
 static int gpiochip_irqchip_init_hw(struct gpio_chip *gc);
 static int gpiochip_irqchip_init_valid_mask(struct gpio_chip *gc);
 static void gpiochip_irqchip_free_valid_mask(struct gpio_chip *gc);
+static int gpiochip_wakeup_irq_setup(struct gpio_chip *gc);
 
 static bool gpiolib_initialized;
 
@@ -1045,8 +1047,15 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 		if (ret)
 			goto err_remove_irqchip;
 	}
+
+	ret = gpiochip_wakeup_irq_setup(gc);
+	if (ret)
+		goto err_remove_device;
+
 	return 0;
 
+err_remove_device:
+	gcdev_unregister(gdev);
 err_remove_irqchip:
 	gpiochip_irqchip_remove(gc);
 err_remove_irqchip_mask:
@@ -1874,6 +1883,84 @@ static int gpiochip_irqchip_add_allocated_domain(struct gpio_chip *gc,
 	return 0;
 }
 
+static irqreturn_t gpio_wake_irq_handler(int irq, void *data)
+{
+	struct irq_data *irq_data = data;
+
+	if (!irq_data || irq != irq_data->irq)
+		return IRQ_NONE;
+
+	return IRQ_HANDLED;
+}
+
+static int gpiochip_wakeup_irq_setup(struct gpio_chip *gc)
+{
+	struct device *dev = gc->parent;
+	struct gpio_irq_chip *girq = &gc->irq;
+	struct gpio_desc *wakeup_gpiod;
+	struct irq_desc *wakeup_irqd;
+	struct irq_domain *irq_domain;
+	struct irq_data *irq_data;
+	unsigned int offset;
+	int wakeup_irq;
+	int ret;
+
+	if (!(device_property_read_bool(dev, "wakeup-source")))
+		return 0;
+
+	irq_domain = girq->domain;
+
+	if (!irq_domain) {
+		dev_err(dev, "Couldn't allocate IRQ domain\n");
+		return -ENXIO;
+	}
+
+	wakeup_gpiod = devm_gpiod_get_optional(dev, "wakeup", GPIOD_IN);
+
+	if (IS_ERR(wakeup_gpiod)) {
+		dev_err(dev, "invalid wakeup gpio: %lu\n", PTR_ERR(wakeup_gpiod));
+		return PTR_ERR(wakeup_gpiod);
+	}
+	if (!wakeup_gpiod) {
+		dev_dbg(dev, "property wakeup-gpios is not defined\n");
+		return 0;
+	}
+
+	offset = gpio_chip_hwgpio(wakeup_gpiod);
+	wakeup_irq = gpiod_to_irq(wakeup_gpiod);
+	if (wakeup_irq < 0) {
+		dev_err(dev, "failed to convert wakeup GPIO to IRQ\n");
+		return wakeup_irq;
+	}
+	irq_domain->ops->map(irq_domain, wakeup_irq, offset);
+	wakeup_irqd = irq_to_desc(wakeup_irq);
+	irq_data = irq_get_irq_data(wakeup_irq);
+	girq->handler = handle_edge_irq;
+
+	if (!(wakeup_irqd->status_use_accessors & IRQ_NOREQUEST)) {
+		device_init_wakeup(dev, 1);
+		ret = devm_request_threaded_irq(dev, wakeup_irq, NULL,
+						gpio_wake_irq_handler,
+						IRQF_TRIGGER_FALLING |
+						IRQF_TRIGGER_RISING |
+						IRQF_ONESHOT |
+						IRQF_SHARED,
+						"pm-wakeup-gpio", irq_data);
+		if (ret) {
+			dev_err(dev, "unable to request wakeup IRQ: %d\n", ret);
+			return ret;
+		}
+	}
+
+	ret = dev_pm_set_wake_irq(dev, wakeup_irq);
+	if (ret) {
+		dev_err(dev, "failed to enable gpio irq wake\n");
+		return ret;
+	}
+
+	return 0;
+}
+
 /**
  * gpiochip_add_irqchip() - adds an IRQ chip to a GPIO chip
  * @gc: the GPIO chip to add the IRQ chip to
-- 
2.25.1