tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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 */
27static struct gpio_desc *reset_gpio;
28static u32 timeout = DEFAULT_TIMEOUT_MS;
29
30static 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
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",
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
79static 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
87static const struct of_device_id of_gpio_poweroff_match[] = {
88 { .compatible = "gpio-poweroff", },
89 {},
90};
91
92static 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
101module_platform_driver(gpio_poweroff_driver);
102
103MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
104MODULE_DESCRIPTION("GPIO poweroff driver");
105MODULE_LICENSE("GPL v2");
106MODULE_ALIAS("platform:poweroff-gpio");