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 #define DEFAULT_TIMEOUT_MS 3000
23 /*
24  * Hold configuration here, cannot be more than one instance of the driver
25  * since pm_power_off itself is global.
26  */
27 static struct gpio_desc *reset_gpio;
28 static u32 timeout = DEFAULT_TIMEOUT_MS;
29 
30 static void gpio_poweroff_do_poweroff(void)
31 {
32 	BUG_ON(!reset_gpio);
33 
34 	/* drive it active, also inactive->active edge */
35 	gpiod_direction_output(reset_gpio, 1);
36 	mdelay(100);
37 	/* drive inactive, also active->inactive edge */
38 	gpiod_set_value_cansleep(reset_gpio, 0);
39 	mdelay(100);
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 
50 static 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",
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, "timeout-ms", &timeout);
70 
71 	reset_gpio = devm_gpiod_get(&pdev->dev, NULL, flags);
72 	if (IS_ERR(reset_gpio))
73 		return PTR_ERR(reset_gpio);
74 
75 	pm_power_off = &gpio_poweroff_do_poweroff;
76 	return 0;
77 }
78 
79 static int gpio_poweroff_remove(struct platform_device *pdev)
80 {
81 	if (pm_power_off == &gpio_poweroff_do_poweroff)
82 		pm_power_off = NULL;
83 
84 	return 0;
85 }
86 
87 static const struct of_device_id of_gpio_poweroff_match[] = {
88 	{ .compatible = "gpio-poweroff", },
89 	{},
90 };
91 
92 static struct platform_driver gpio_poweroff_driver = {
93 	.probe = gpio_poweroff_probe,
94 	.remove = gpio_poweroff_remove,
95 	.driver = {
96 		.name = "poweroff-gpio",
97 		.of_match_table = of_gpio_poweroff_match,
98 	},
99 };
100 
101 module_platform_driver(gpio_poweroff_driver);
102 
103 MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
104 MODULE_DESCRIPTION("GPIO poweroff driver");
105 MODULE_LICENSE("GPL v2");
106 MODULE_ALIAS("platform:poweroff-gpio");
107