gpiolib-acpi: Add ACPI5 event model support to gpio.

Add ability to handle ACPI events signalled by GPIO interrupts.

ACPI5 platforms can use GPIO signaled ACPI events. These GPIO interrupts are
handled by ACPI event methods which need to be called from the GPIO
controller's interrupt handler. acpi_gpio_request_interrupt() finds out which
gpio pins have acpi event methods and assigns interrupt handlers that calls
the acpi event methods for those pins.

Partially based on work by Rui Zhang <rui.zhang@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib-acpi.c

@@ -15,6 +15,7 @@
 #include <linux/export.h>
 #include <linux/acpi_gpio.h>
 #include <linux/acpi.h>
+#include <linux/interrupt.h>
 
 static int acpi_gpiochip_find(struct gpio_chip *gc, void *data)
 {
@@ -52,3 +53,84 @@ int acpi_get_gpio(char *path, int pin)
 	return chip->base + pin;
 }
 EXPORT_SYMBOL_GPL(acpi_get_gpio);
+
+
+static irqreturn_t acpi_gpio_irq_handler(int irq, void *data)
+{
+	acpi_handle handle = data;
+
+	acpi_evaluate_object(handle, NULL, NULL, NULL);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * acpi_gpiochip_request_interrupts() - Register isr for gpio chip ACPI events
+ * @chip:      gpio chip
+ *
+ * ACPI5 platforms can use GPIO signaled ACPI events. These GPIO interrupts are
+ * handled by ACPI event methods which need to be called from the GPIO
+ * chip's interrupt handler. acpi_gpiochip_request_interrupts finds out which
+ * gpio pins have acpi event methods and assigns interrupt handlers that calls
+ * the acpi event methods for those pins.
+ *
+ * Interrupts are automatically freed on driver detach
+ */
+
+void acpi_gpiochip_request_interrupts(struct gpio_chip *chip)
+{
+	struct acpi_buffer buf = {ACPI_ALLOCATE_BUFFER, NULL};
+	struct acpi_resource *res;
+	acpi_handle handle, ev_handle;
+	acpi_status status;
+	unsigned int pin, irq;
+	char ev_name[5];
+
+	if (!chip->dev || !chip->to_irq)
+		return;
+
+	handle = ACPI_HANDLE(chip->dev);
+	if (!handle)
+		return;
+
+	status = acpi_get_event_resources(handle, &buf);
+	if (ACPI_FAILURE(status))
+		return;
+
+	/* If a gpio interrupt has an acpi event handler method, then
+	 * set up an interrupt handler that calls the acpi event handler
+	 */
+
+	for (res = buf.pointer;
+	     res && (res->type != ACPI_RESOURCE_TYPE_END_TAG);
+	     res = ACPI_NEXT_RESOURCE(res)) {
+
+		if (res->type != ACPI_RESOURCE_TYPE_GPIO ||
+		    res->data.gpio.connection_type !=
+		    ACPI_RESOURCE_GPIO_TYPE_INT)
+			continue;
+
+		pin = res->data.gpio.pin_table[0];
+		if (pin > chip->ngpio)
+			continue;
+
+		sprintf(ev_name, "_%c%02X",
+		res->data.gpio.triggering ? 'E' : 'L', pin);
+
+		status = acpi_get_handle(handle, ev_name, &ev_handle);
+		if (ACPI_FAILURE(status))
+			continue;
+
+		irq = chip->to_irq(chip, pin);
+		if (irq < 0)
+			continue;
+
+		/* Assume BIOS sets the triggering, so no flags */
+		devm_request_threaded_irq(chip->dev, irq, NULL,
+					  acpi_gpio_irq_handler,
+					  0,
+					  "GPIO-signaled-ACPI-event",
+					  ev_handle);
+	}
+}
+EXPORT_SYMBOL(acpi_gpiochip_request_interrupts);

include/linux/acpi_gpio.h

@@ -2,10 +2,12 @@
 #define _LINUX_ACPI_GPIO_H_
 
 #include <linux/errno.h>
+#include <linux/gpio.h>
 
 #ifdef CONFIG_GPIO_ACPI
 
 int acpi_get_gpio(char *path, int pin);
+void acpi_gpiochip_request_interrupts(struct gpio_chip *chip);
 
 #else /* CONFIG_GPIO_ACPI */
 
@@ -14,6 +16,8 @@ static inline int acpi_get_gpio(char *path, int pin)
 	return -ENODEV;
 }
 
+static inline void acpi_gpiochip_request_interrupts(struct gpio_chip *chip) { }
+
 #endif /* CONFIG_GPIO_ACPI */
 
 #endif /* _LINUX_ACPI_GPIO_H_ */