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