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
gpio_poweroff_do_poweroff(void)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
gpio_poweroff_probe(struct platform_device * pdev)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
gpio_poweroff_remove(struct platform_device * pdev)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