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/gpio/consumer.h>
15#include <linux/of_platform.h>
16#include <linux/module.h>
17
18#define DEFAULT_TIMEOUT_MS 3000
19/*
20 * Hold configuration here, cannot be more than one instance of the driver
21 * since pm_power_off itself is global.
22 */
23static struct gpio_desc *reset_gpio;
24static u32 timeout = DEFAULT_TIMEOUT_MS;
25static u32 active_delay = 100;
26static u32 inactive_delay = 100;
27
28static void gpio_poweroff_do_poweroff(void)
29{
30	BUG_ON(!reset_gpio);
31
32	/* drive it active, also inactive->active edge */
33	gpiod_direction_output(reset_gpio, 1);
34	mdelay(active_delay);
35
36	/* drive inactive, also active->inactive edge */
37	gpiod_set_value_cansleep(reset_gpio, 0);
38	mdelay(inactive_delay);
39
40	/* drive it active, also inactive->active edge */
41	gpiod_set_value_cansleep(reset_gpio, 1);
42
43	/* give it some time */
44	mdelay(timeout);
45
46	WARN_ON(1);
47}
48
49static int gpio_poweroff_probe(struct platform_device *pdev)
50{
51	bool input = false;
52	enum gpiod_flags flags;
53
54	/* If a pm_power_off function has already been added, leave it alone */
55	if (pm_power_off != NULL) {
56		dev_err(&pdev->dev,
57			"%s: pm_power_off function already registered\n",
58		       __func__);
59		return -EBUSY;
60	}
61
62	input = device_property_read_bool(&pdev->dev, "input");
63	if (input)
64		flags = GPIOD_IN;
65	else
66		flags = GPIOD_OUT_LOW;
67
68	device_property_read_u32(&pdev->dev, "active-delay-ms", &active_delay);
69	device_property_read_u32(&pdev->dev, "inactive-delay-ms",
70				 &inactive_delay);
71	device_property_read_u32(&pdev->dev, "timeout-ms", &timeout);
72
73	reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
74	if (IS_ERR(reset_gpio))
75		return PTR_ERR(reset_gpio);
76
77	pm_power_off = &gpio_poweroff_do_poweroff;
78	return 0;
79}
80
81static int gpio_poweroff_remove(struct platform_device *pdev)
82{
83	if (pm_power_off == &gpio_poweroff_do_poweroff)
84		pm_power_off = NULL;
85
86	return 0;
87}
88
89static const struct of_device_id of_gpio_poweroff_match[] = {
90	{ .compatible = "gpio-poweroff", },
91	{},
92};
93MODULE_DEVICE_TABLE(of, of_gpio_poweroff_match);
94
95static struct platform_driver gpio_poweroff_driver = {
96	.probe = gpio_poweroff_probe,
97	.remove = gpio_poweroff_remove,
98	.driver = {
99		.name = "poweroff-gpio",
100		.of_match_table = of_gpio_poweroff_match,
101	},
102};
103
104module_platform_driver(gpio_poweroff_driver);
105
106MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
107MODULE_DESCRIPTION("GPIO poweroff driver");
108MODULE_LICENSE("GPL v2");
109MODULE_ALIAS("platform:poweroff-gpio");
110