[go: nahoru, domu]
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 */
26static struct gpio_desc *reset_gpio;
27
28static 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
48static int gpio_poweroff_probe(struct platform_device *pdev)
49{
50	bool input = false;
51
52	/* If a pm_power_off function has already been added, leave it alone */
53	if (pm_power_off != NULL) {
54		dev_err(&pdev->dev,
55			"%s: pm_power_off function already registered",
56		       __func__);
57		return -EBUSY;
58	}
59
60	reset_gpio = devm_gpiod_get(&pdev->dev, NULL);
61	if (IS_ERR(reset_gpio))
62		return PTR_ERR(reset_gpio);
63
64	input = of_property_read_bool(pdev->dev.of_node, "input");
65
66	if (input) {
67		if (gpiod_direction_input(reset_gpio)) {
68			dev_err(&pdev->dev,
69				"Could not set direction of reset GPIO to input\n");
70			return -ENODEV;
71		}
72	} else {
73		if (gpiod_direction_output(reset_gpio, 0)) {
74			dev_err(&pdev->dev,
75				"Could not set direction of reset GPIO\n");
76			return -ENODEV;
77		}
78	}
79
80	pm_power_off = &gpio_poweroff_do_poweroff;
81	return 0;
82}
83
84static int gpio_poweroff_remove(struct platform_device *pdev)
85{
86	if (pm_power_off == &gpio_poweroff_do_poweroff)
87		pm_power_off = NULL;
88
89	return 0;
90}
91
92static const struct of_device_id of_gpio_poweroff_match[] = {
93	{ .compatible = "gpio-poweroff", },
94	{},
95};
96
97static struct platform_driver gpio_poweroff_driver = {
98	.probe = gpio_poweroff_probe,
99	.remove = gpio_poweroff_remove,
100	.driver = {
101		.name = "poweroff-gpio",
102		.owner = THIS_MODULE,
103		.of_match_table = of_gpio_poweroff_match,
104	},
105};
106
107module_platform_driver(gpio_poweroff_driver);
108
109MODULE_AUTHOR("Jamie Lentin <jm@lentin.co.uk>");
110MODULE_DESCRIPTION("GPIO poweroff driver");
111MODULE_LICENSE("GPL v2");
112MODULE_ALIAS("platform:poweroff-gpio");
113