1/*
2 * Toggles a GPIO pin to restart a device
3 *
4 * Copyright (C) 2014 Google, Inc.
5 *
6 * This software is licensed under the terms of the GNU General Public
7 * License version 2, as published by the Free Software Foundation, and
8 * may be copied, distributed, and modified under those terms.
9 *
10 * This program is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13 * GNU General Public License for more details.
14 *
15 * Based on the gpio-poweroff driver.
16 */
17#include <linux/reboot.h>
18#include <linux/kernel.h>
19#include <linux/init.h>
20#include <linux/delay.h>
21#include <linux/platform_device.h>
22#include <linux/gpio/consumer.h>
23#include <linux/of_platform.h>
24#include <linux/module.h>
25
26struct gpio_restart {
27	struct gpio_desc *reset_gpio;
28	struct notifier_block restart_handler;
29	u32 active_delay_ms;
30	u32 inactive_delay_ms;
31	u32 wait_delay_ms;
32};
33
34static int gpio_restart_notify(struct notifier_block *this,
35				unsigned long mode, void *cmd)
36{
37	struct gpio_restart *gpio_restart =
38		container_of(this, struct gpio_restart, restart_handler);
39
40	/* drive it active, also inactive->active edge */
41	gpiod_direction_output(gpio_restart->reset_gpio, 1);
42	mdelay(gpio_restart->active_delay_ms);
43
44	/* drive inactive, also active->inactive edge */
45	gpiod_set_value(gpio_restart->reset_gpio, 0);
46	mdelay(gpio_restart->inactive_delay_ms);
47
48	/* drive it active, also inactive->active edge */
49	gpiod_set_value(gpio_restart->reset_gpio, 1);
50
51	/* give it some time */
52	mdelay(gpio_restart->wait_delay_ms);
53
54	WARN_ON(1);
55
56	return NOTIFY_DONE;
57}
58
59static int gpio_restart_probe(struct platform_device *pdev)
60{
61	struct gpio_restart *gpio_restart;
62	bool open_source = false;
63	u32 property;
64	int ret;
65
66	gpio_restart = devm_kzalloc(&pdev->dev, sizeof(*gpio_restart),
67			GFP_KERNEL);
68	if (!gpio_restart)
69		return -ENOMEM;
70
71	open_source = of_property_read_bool(pdev->dev.of_node, "open-source");
72
73	gpio_restart->reset_gpio = devm_gpiod_get(&pdev->dev, NULL,
74			open_source ? GPIOD_IN : GPIOD_OUT_LOW);
75	if (IS_ERR(gpio_restart->reset_gpio)) {
76		dev_err(&pdev->dev, "Could net get reset GPIO\n");
77		return PTR_ERR(gpio_restart->reset_gpio);
78	}
79
80	gpio_restart->restart_handler.notifier_call = gpio_restart_notify;
81	gpio_restart->restart_handler.priority = 129;
82	gpio_restart->active_delay_ms = 100;
83	gpio_restart->inactive_delay_ms = 100;
84	gpio_restart->wait_delay_ms = 3000;
85
86	ret = of_property_read_u32(pdev->dev.of_node, "priority", &property);
87	if (!ret) {
88		if (property > 255)
89			dev_err(&pdev->dev, "Invalid priority property: %u\n",
90					property);
91		else
92			gpio_restart->restart_handler.priority = property;
93	}
94
95	of_property_read_u32(pdev->dev.of_node, "active-delay",
96			&gpio_restart->active_delay_ms);
97	of_property_read_u32(pdev->dev.of_node, "inactive-delay",
98			&gpio_restart->inactive_delay_ms);
99	of_property_read_u32(pdev->dev.of_node, "wait-delay",
100			&gpio_restart->wait_delay_ms);
101
102	platform_set_drvdata(pdev, gpio_restart);
103
104	ret = register_restart_handler(&gpio_restart->restart_handler);
105	if (ret) {
106		dev_err(&pdev->dev, "%s: cannot register restart handler, %d\n",
107				__func__, ret);
108		return -ENODEV;
109	}
110
111	return 0;
112}
113
114static int gpio_restart_remove(struct platform_device *pdev)
115{
116	struct gpio_restart *gpio_restart = platform_get_drvdata(pdev);
117	int ret;
118
119	ret = unregister_restart_handler(&gpio_restart->restart_handler);
120	if (ret) {
121		dev_err(&pdev->dev,
122				"%s: cannot unregister restart handler, %d\n",
123				__func__, ret);
124		return -ENODEV;
125	}
126
127	return 0;
128}
129
130static const struct of_device_id of_gpio_restart_match[] = {
131	{ .compatible = "gpio-restart", },
132	{},
133};
134
135static struct platform_driver gpio_restart_driver = {
136	.probe = gpio_restart_probe,
137	.remove = gpio_restart_remove,
138	.driver = {
139		.name = "restart-gpio",
140		.of_match_table = of_gpio_restart_match,
141	},
142};
143
144module_platform_driver(gpio_restart_driver);
145
146MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
147MODULE_DESCRIPTION("GPIO restart driver");
148MODULE_LICENSE("GPL");
149