gpio-poweroff.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Toggles a GPIO pin to power down a device
  4 *
  5 * Jamie Lentin <jm@lentin.co.uk>
  6 * Andrew Lunn <andrew@lunn.ch>
  7 *
  8 * Copyright (C) 2012 Jamie Lentin
  9 */
 10#include <linux/kernel.h>
 11#include <linux/init.h>
 12#include <linux/delay.h>
 13#include <linux/platform_device.h>
 14#include <linux/property.h>
 15#include <linux/gpio/consumer.h>
 16#include <linux/mod_devicetable.h>
 17#include <linux/module.h>
 18#include <linux/reboot.h>
 19
 20#define DEFAULT_TIMEOUT_MS 3000
 21
 22struct gpio_poweroff {
 23	struct gpio_desc *reset_gpio;
 24	u32 timeout_ms;
 25	u32 active_delay_ms;
 26	u32 inactive_delay_ms;
 27};
 28
 29static int gpio_poweroff_do_poweroff(struct sys_off_data *data)
 30{
 31	struct gpio_poweroff *gpio_poweroff = data->cb_data;
 32
 33	/* drive it active, also inactive->active edge */
 34	gpiod_direction_output(gpio_poweroff->reset_gpio, 1);
 35	mdelay(gpio_poweroff->active_delay_ms);
 36
 37	/* drive inactive, also active->inactive edge */
 38	gpiod_set_value_cansleep(gpio_poweroff->reset_gpio, 0);
 39	mdelay(gpio_poweroff->inactive_delay_ms);
 40
 41	/* drive it active, also inactive->active edge */
 42	gpiod_set_value_cansleep(gpio_poweroff->reset_gpio, 1);
 43
 44	/* give it some time */
 45	mdelay(gpio_poweroff->timeout_ms);
 46
 47	/*
 48	 * If code reaches this point, it means that gpio-poweroff has failed
 49	 * to actually power off the system.
 50	 * Warn the user that the attempt to poweroff via gpio-poweroff
 51	 * has gone wrong.
 52	 */
 53	WARN(1, "Failed to poweroff via gpio-poweroff mechanism\n");
 54
 55	return NOTIFY_DONE;
 56}
 57
 58static int gpio_poweroff_probe(struct platform_device *pdev)
 59{
 60	struct gpio_poweroff *gpio_poweroff;
 61	bool input = false;
 62	enum gpiod_flags flags;
 63	int priority = SYS_OFF_PRIO_DEFAULT;
 64	int ret;
 65
 66	gpio_poweroff = devm_kzalloc(&pdev->dev, sizeof(*gpio_poweroff), GFP_KERNEL);
 67	if (!gpio_poweroff)
 68		return -ENOMEM;
 69
 70	input = device_property_read_bool(&pdev->dev, "input");
 71	if (input)
 72		flags = GPIOD_IN;
 73	else
 74		flags = GPIOD_OUT_LOW;
 75
 76
 77	gpio_poweroff->active_delay_ms = 100;
 78	gpio_poweroff->inactive_delay_ms = 100;
 79	gpio_poweroff->timeout_ms = DEFAULT_TIMEOUT_MS;
 80
 81	device_property_read_u32(&pdev->dev, "active-delay-ms", &gpio_poweroff->active_delay_ms);
 82	device_property_read_u32(&pdev->dev, "inactive-delay-ms",
 83				 &gpio_poweroff->inactive_delay_ms);
 84	device_property_read_u32(&pdev->dev, "timeout-ms", &gpio_poweroff->timeout_ms);
 85	device_property_read_u32(&pdev->dev, "priority", &priority);
 86	if (priority > 255) {
 87		dev_err(&pdev->dev, "Invalid priority property: %u\n", priority);
 88		return -EINVAL;
 89	}
 90
 91	gpio_poweroff->reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
 92	if (IS_ERR(gpio_poweroff->reset_gpio))
 93		return PTR_ERR(gpio_poweroff->reset_gpio);
 94
 95	ret = devm_register_sys_off_handler(&pdev->dev, SYS_OFF_MODE_POWER_OFF,
 96					    priority, gpio_poweroff_do_poweroff, gpio_poweroff);
 97	if (ret)
 98		return dev_err_probe(&pdev->dev, ret, "Cannot register poweroff handler\n");
 99
100	return 0;
101}
102
103static const struct of_device_id of_gpio_poweroff_match[] = {
104	{ .compatible = "gpio-poweroff", },
105	{},
106};
107MODULE_DEVICE_TABLE(of, of_gpio_poweroff_match);
108
109static struct platform_driver gpio_poweroff_driver = {
110	.probe = gpio_poweroff_probe,
111	.driver = {
112		.name = "poweroff-gpio",
113		.of_match_table = of_gpio_poweroff_match,
114	},
115};
116
117module_platform_driver(gpio_poweroff_driver);
118
119MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
120MODULE_DESCRIPTION("GPIO poweroff driver");
121MODULE_ALIAS("platform:poweroff-gpio");