1 /*
2  * Toggles a GPIO pin to power down a device
3  *
4  * Jamie Lentin <jm@lentin.co.uk>
5  * Andrew Lunn <andrew@lunn.ch>
6  *
7  * Copyright (C) 2012 Jamie Lentin
8  *
9  * This program is free software; you can redistribute it and/or modify
10  * it under the terms of the GNU General Public License version 2 as
11  * published by the Free Software Foundation.
12  *
13  */
14 #include <linux/kernel.h>
15 #include <linux/init.h>
16 #include <linux/delay.h>
17 #include <linux/platform_device.h>
18 #include <linux/gpio/consumer.h>
19 #include <linux/of_platform.h>
20 #include <linux/module.h>
21 
22 /*
23  * Hold configuration here, cannot be more than one instance of the driver
24  * since pm_power_off itself is global.
25  */
26 static struct gpio_desc *reset_gpio;
27 
28 static 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(100);
35 	/* drive inactive, also active->inactive edge */
36 	gpiod_set_value(reset_gpio, 0);
37 	mdelay(100);
38 
39 	/* drive it active, also inactive->active edge */
40 	gpiod_set_value(reset_gpio, 1);
41 
42 	/* give it some time */
43 	mdelay(3000);
44 
45 	WARN_ON(1);
46 }
47 
48 static int gpio_poweroff_probe(struct platform_device *pdev)
49 {
50 	bool input = false;
51 	enum gpiod_flags flags;
52 
53 	/* If a pm_power_off function has already been added, leave it alone */
54 	if (pm_power_off != NULL) {
55 		dev_err(&pdev->dev,
56 			"%s: pm_power_off function already registered",
57 		       __func__);
58 		return -EBUSY;
59 	}
60 
61 	input = of_property_read_bool(pdev->dev.of_node, "input");
62 	if (input)
63 		flags = GPIOD_IN;
64 	else
65 		flags = GPIOD_OUT_LOW;
66 
67 	reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
68 	if (IS_ERR(reset_gpio))
69 		return PTR_ERR(reset_gpio);
70 
71 	pm_power_off = &gpio_poweroff_do_poweroff;
72 	return 0;
73 }
74 
75 static int gpio_poweroff_remove(struct platform_device *pdev)
76 {
77 	if (pm_power_off == &gpio_poweroff_do_poweroff)
78 		pm_power_off = NULL;
79 
80 	return 0;
81 }
82 
83 static const struct of_device_id of_gpio_poweroff_match[] = {
84 	{ .compatible = "gpio-poweroff", },
85 	{},
86 };
87 
88 static struct platform_driver gpio_poweroff_driver = {
89 	.probe = gpio_poweroff_probe,
90 	.remove = gpio_poweroff_remove,
91 	.driver = {
92 		.name = "poweroff-gpio",
93 		.of_match_table = of_gpio_poweroff_match,
94 	},
95 };
96 
97 module_platform_driver(gpio_poweroff_driver);
98 
99 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
100 MODULE_DESCRIPTION("GPIO poweroff driver");
101 MODULE_LICENSE("GPL v2");
102 MODULE_ALIAS("platform:poweroff-gpio");
103