[PATCH 11/12] gpiolib: acpi: Add dedicated ACPI GPIO events module

["Marco Scardovi (scardracs)" <mscardovi95@gmail.com>]

Assisted-by: Antigravity:gemini-3-flash
Signed-off-by: Marco Scardovi <mscardovi95@gmail.com>
---
 drivers/gpio/Makefile              |   2 +-
 drivers/gpio/gpiolib-acpi-events.c | 309 +++++++++++++++++++++++++++++
 2 files changed, 310 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpio/gpiolib-acpi-events.c

diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 1a416305465b..75b38577b328 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -10,7 +10,7 @@ obj-$(CONFIG_OF_GPIO)		+= gpiolib-of.o
 obj-$(CONFIG_GPIO_CDEV)		+= gpiolib-cdev.o
 obj-$(CONFIG_GPIO_SYSFS)	+= gpiolib-sysfs.o
 obj-$(CONFIG_GPIO_ACPI)		+= gpiolib-acpi.o
-gpiolib-acpi-y			:= gpiolib-acpi-core.o gpiolib-acpi-quirks.o gpiolib-acpi-opregion.o
+gpiolib-acpi-y			:= gpiolib-acpi-core.o gpiolib-acpi-quirks.o gpiolib-acpi-opregion.o gpiolib-acpi-events.o
 obj-$(CONFIG_GPIOLIB)		+= gpiolib-swnode.o
 obj-$(CONFIG_GPIO_SHARED)	+= gpiolib-shared.o
 
diff --git a/drivers/gpio/gpiolib-acpi-events.c b/drivers/gpio/gpiolib-acpi-events.c
new file mode 100644
index 000000000000..317528a25c92
--- /dev/null
+++ b/drivers/gpio/gpiolib-acpi-events.c
@@ -0,0 +1,309 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * ACPI Event and Interrupt helper for GPIO API
+ *
+ * Copyright (C) 2026, Intel Corporation
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+
+#include "gpiolib.h"
+#include "gpiolib-acpi.h"
+
+static irqreturn_t acpi_gpio_irq_handler(int irq, void *data)
+{
+	struct acpi_gpio_event *event = data;
+
+	acpi_evaluate_object(event->handle, NULL, NULL, NULL);
+
+	return IRQ_HANDLED;
+}
+
+static irqreturn_t acpi_gpio_irq_handler_evt(int irq, void *data)
+{
+	struct acpi_gpio_event *event = data;
+
+	acpi_execute_simple_method(event->handle, NULL, event->pin);
+
+	return IRQ_HANDLED;
+}
+
+static void acpi_gpiochip_request_irq(struct acpi_gpio_chip *acpi_gpio,
+				      struct acpi_gpio_event *event)
+{
+	struct device *parent = acpi_gpio->chip->parent;
+	int ret, value;
+
+	ret = request_threaded_irq(event->irq, NULL, event->handler,
+				   event->irqflags | IRQF_ONESHOT, "ACPI:Event", event);
+	if (ret) {
+		dev_err(parent, "Failed to setup interrupt handler for %d\n", event->irq);
+		return;
+	}
+
+	if (event->irq_is_wake)
+		enable_irq_wake(event->irq);
+
+	event->irq_requested = true;
+
+	/*
+	 * Make sure we trigger the initial state of ActiveBoth IRQs.
+	 *
+	 * According to the Microsoft GPIO documentation, triggering GPIO
+	 * interrupts marked as ActiveBoth during initialization is correct
+	 * as long as the associated GPIO line is already "asserted"
+	 * (logic level low). We should not trigger edge-based GPIO
+	 * interrupts not marked as ActiveBoth.
+	 *
+	 * See: https://learn.microsoft.com/en-us/windows-hardware/drivers/bringup/general-purpose-i-o--gpio-
+	 * Section: "GPIO controllers and ActiveBoth interrupts"
+	 */
+	if (acpi_gpio_need_run_edge_events_on_boot() &&
+	    ((event->irqflags & (IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING)) ==
+	     (IRQF_TRIGGER_RISING | IRQF_TRIGGER_FALLING))) {
+		value = gpiod_get_raw_value_cansleep(event->desc);
+		if (value == 0)
+			event->handler(event->irq, event);
+	}
+}
+
+static void acpi_gpiochip_request_irqs(struct acpi_gpio_chip *acpi_gpio)
+{
+	struct acpi_gpio_event *event;
+
+	list_for_each_entry(event, &acpi_gpio->events, node)
+		acpi_gpiochip_request_irq(acpi_gpio, event);
+}
+
+bool acpi_gpio_irq_is_wake(struct device *parent,
+			   const struct acpi_resource_gpio *agpio)
+{
+	unsigned int pin;
+
+	if (agpio->pin_table_length == 0)
+		return false;
+
+	pin = agpio->pin_table[0];
+
+	if (agpio->wake_capable != ACPI_WAKE_CAPABLE)
+		return false;
+
+	if (acpi_gpio_in_ignore_list(ACPI_GPIO_IGNORE_WAKE, dev_name(parent), pin)) {
+		dev_info(parent, "Ignoring wakeup on pin %u\n", pin);
+		return false;
+	}
+
+	return true;
+}
+
+/* Always returns AE_OK so that we keep looping over the resources */
+static acpi_status acpi_gpiochip_alloc_event(struct acpi_resource *ares,
+					     void *context)
+{
+	struct acpi_gpio_chip *acpi_gpio = context;
+	struct gpio_chip *chip = acpi_gpio->chip;
+	struct acpi_resource_gpio *agpio;
+	acpi_handle handle, evt_handle;
+	struct acpi_gpio_event *event;
+	irq_handler_t handler = NULL;
+	struct gpio_desc *desc;
+	unsigned int pin;
+	int ret, irq;
+
+	if (!acpi_gpio_get_irq_resource(ares, &agpio))
+		return AE_OK;
+
+	if (agpio->pin_table_length == 0)
+		return AE_OK;
+
+	handle = ACPI_HANDLE(chip->parent);
+	pin = agpio->pin_table[0];
+
+	if (pin <= 255) {
+		char ev_name[8];
+
+		snprintf(ev_name, sizeof(ev_name), "_%c%02X",
+			 agpio->triggering == ACPI_EDGE_SENSITIVE ? 'E' : 'L',
+			 pin);
+		if (ACPI_SUCCESS(acpi_get_handle(handle, ev_name, &evt_handle)))
+			handler = acpi_gpio_irq_handler;
+	}
+	if (!handler) {
+		if (ACPI_SUCCESS(acpi_get_handle(handle, "_EVT", &evt_handle)))
+			handler = acpi_gpio_irq_handler_evt;
+	}
+	if (!handler)
+		return AE_OK;
+
+	if (acpi_gpio_in_ignore_list(ACPI_GPIO_IGNORE_INTERRUPT, dev_name(chip->parent), pin)) {
+		dev_info(chip->parent, "Ignoring interrupt on pin %u\n", pin);
+		return AE_OK;
+	}
+
+	desc = acpi_request_own_gpiod(chip, agpio, 0, "ACPI:Event");
+	if (IS_ERR(desc)) {
+		dev_err(chip->parent,
+			"Failed to request GPIO for pin 0x%04X, err %pe\n",
+			pin, desc);
+		return AE_OK;
+	}
+
+	ret = gpiochip_lock_as_irq(chip, pin);
+	if (ret) {
+		dev_err(chip->parent,
+			"Failed to lock GPIO pin 0x%04X as interrupt, err %d\n",
+			pin, ret);
+		goto fail_free_desc;
+	}
+
+	irq = gpiod_to_irq(desc);
+	if (irq < 0) {
+		dev_err(chip->parent,
+			"Failed to translate GPIO pin 0x%04X to IRQ, err %d\n",
+			pin, irq);
+		goto fail_unlock_irq;
+	}
+
+	event = kzalloc_obj(*event);
+	if (!event)
+		goto fail_unlock_irq;
+
+	event->irqflags = IRQF_ONESHOT;
+	if (agpio->triggering == ACPI_LEVEL_SENSITIVE) {
+		if (agpio->polarity == ACPI_ACTIVE_HIGH)
+			event->irqflags |= IRQF_TRIGGER_HIGH;
+		else
+			event->irqflags |= IRQF_TRIGGER_LOW;
+	} else {
+		switch (agpio->polarity) {
+		case ACPI_ACTIVE_HIGH:
+			event->irqflags |= IRQF_TRIGGER_RISING;
+			break;
+		case ACPI_ACTIVE_LOW:
+			event->irqflags |= IRQF_TRIGGER_FALLING;
+			break;
+		default:
+			event->irqflags |= IRQF_TRIGGER_RISING |
+					   IRQF_TRIGGER_FALLING;
+			break;
+		}
+	}
+
+	event->handle = evt_handle;
+	event->handler = handler;
+	event->irq = irq;
+	event->irq_is_wake = acpi_gpio_irq_is_wake(chip->parent, agpio);
+	event->pin = pin;
+	event->desc = desc;
+
+	list_add_tail(&event->node, &acpi_gpio->events);
+
+	return AE_OK;
+
+fail_unlock_irq:
+	gpiochip_unlock_as_irq(chip, pin);
+fail_free_desc:
+	gpiochip_free_own_desc(desc);
+
+	return AE_OK;
+}
+
+/**
+ * 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.
+ */
+void acpi_gpiochip_request_interrupts(struct gpio_chip *chip)
+{
+	struct acpi_gpio_chip *acpi_gpio;
+	acpi_handle handle;
+	acpi_status status;
+
+	if (!chip->parent || !chip->to_irq)
+		return;
+
+	handle = ACPI_HANDLE(chip->parent);
+	if (!handle)
+		return;
+
+	status = acpi_get_data(handle, acpi_gpio_chip_dh, (void **)&acpi_gpio);
+	if (ACPI_FAILURE(status))
+		return;
+
+	if (acpi_quirk_skip_gpio_event_handlers())
+		return;
+
+	acpi_walk_resources(handle, METHOD_NAME__AEI,
+			    acpi_gpiochip_alloc_event, acpi_gpio);
+
+	if (acpi_gpio_add_to_deferred_list(&acpi_gpio->deferred_req_irqs_list_entry))
+		return;
+
+	acpi_gpiochip_request_irqs(acpi_gpio);
+}
+EXPORT_SYMBOL_GPL(acpi_gpiochip_request_interrupts);
+
+/**
+ * acpi_gpiochip_free_interrupts() - Free GPIO ACPI event interrupts.
+ * @chip:      GPIO chip
+ *
+ * Free interrupts associated with GPIO ACPI event method for the given
+ * GPIO chip.
+ */
+void acpi_gpiochip_free_interrupts(struct gpio_chip *chip)
+{
+	struct acpi_gpio_chip *acpi_gpio;
+	struct acpi_gpio_event *event, *ep;
+	acpi_handle handle;
+	acpi_status status;
+
+	if (!chip->parent || !chip->to_irq)
+		return;
+
+	handle = ACPI_HANDLE(chip->parent);
+	if (!handle)
+		return;
+
+	status = acpi_get_data(handle, acpi_gpio_chip_dh, (void **)&acpi_gpio);
+	if (ACPI_FAILURE(status))
+		return;
+
+	acpi_gpio_remove_from_deferred_list(&acpi_gpio->deferred_req_irqs_list_entry);
+
+	list_for_each_entry_safe_reverse(event, ep, &acpi_gpio->events, node) {
+		if (event->irq_requested) {
+			if (event->irq_is_wake)
+				disable_irq_wake(event->irq);
+
+			free_irq(event->irq, event);
+		}
+
+		gpiochip_unlock_as_irq(chip, event->pin);
+		gpiochip_free_own_desc(event->desc);
+		list_del(&event->node);
+		kfree(event);
+	}
+}
+EXPORT_SYMBOL_GPL(acpi_gpiochip_free_interrupts);
+
+void __init acpi_gpio_process_deferred_list(struct list_head *list)
+{
+	struct acpi_gpio_chip *acpi_gpio, *tmp;
+
+	list_for_each_entry_safe(acpi_gpio, tmp, list, deferred_req_irqs_list_entry)
+		acpi_gpiochip_request_irqs(acpi_gpio);
+}
-- 
2.54.0