1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Toggles a GPIO pin to restart a device
4 *
5 * Copyright (C) 2014 Google, Inc.
6 *
7 * Based on the gpio-poweroff driver.
8 */
9#include <linux/reboot.h>
10#include <linux/kernel.h>
11#include <linux/init.h>
12#include <linux/delay.h>
13#include <linux/platform_device.h>
14#include <linux/gpio/consumer.h>
15#include <linux/module.h>
16#include <linux/of.h>
17
18struct gpio_restart {
19	struct gpio_desc *reset_gpio;
20	struct notifier_block restart_handler;
21	u32 active_delay_ms;
22	u32 inactive_delay_ms;
23	u32 wait_delay_ms;
24};
25
26static int gpio_restart_notify(struct notifier_block *this,
27				unsigned long mode, void *cmd)
28{
29	struct gpio_restart *gpio_restart =
30		container_of(this, struct gpio_restart, restart_handler);
31
32	/* drive it active, also inactive->active edge */
33	gpiod_direction_output(gpio_restart->reset_gpio, 1);
34	mdelay(gpio_restart->active_delay_ms);
35
36	/* drive inactive, also active->inactive edge */
37	gpiod_set_value(gpio_restart->reset_gpio, 0);
38	mdelay(gpio_restart->inactive_delay_ms);
39
40	/* drive it active, also inactive->active edge */
41	gpiod_set_value(gpio_restart->reset_gpio, 1);
42
43	/* give it some time */
44	mdelay(gpio_restart->wait_delay_ms);
45
46	WARN_ON(1);
47
48	return NOTIFY_DONE;
49}
50
51static int gpio_restart_probe(struct platform_device *pdev)
52{
53	struct gpio_restart *gpio_restart;
54	bool open_source = false;
55	u32 property;
56	int ret;
57
58	gpio_restart = devm_kzalloc(&pdev->dev, sizeof(*gpio_restart),
59			GFP_KERNEL);
60	if (!gpio_restart)
61		return -ENOMEM;
62
63	open_source = of_property_read_bool(pdev->dev.of_node, "open-source");
64
65	gpio_restart->reset_gpio = devm_gpiod_get(&pdev->dev, NULL,
66			open_source ? GPIOD_IN : GPIOD_OUT_LOW);
67	ret = PTR_ERR_OR_ZERO(gpio_restart->reset_gpio);
68	if (ret) {
69		if (ret != -EPROBE_DEFER)
70			dev_err(&pdev->dev, "Could not get reset GPIO\n");
71		return ret;
72	}
73
74	gpio_restart->restart_handler.notifier_call = gpio_restart_notify;
75	gpio_restart->restart_handler.priority = 129;
76	gpio_restart->active_delay_ms = 100;
77	gpio_restart->inactive_delay_ms = 100;
78	gpio_restart->wait_delay_ms = 3000;
79
80	ret = of_property_read_u32(pdev->dev.of_node, "priority", &property);
81	if (!ret) {
82		if (property > 255)
83			dev_err(&pdev->dev, "Invalid priority property: %u\n",
84					property);
85		else
86			gpio_restart->restart_handler.priority = property;
87	}
88
89	of_property_read_u32(pdev->dev.of_node, "active-delay",
90			&gpio_restart->active_delay_ms);
91	of_property_read_u32(pdev->dev.of_node, "inactive-delay",
92			&gpio_restart->inactive_delay_ms);
93	of_property_read_u32(pdev->dev.of_node, "wait-delay",
94			&gpio_restart->wait_delay_ms);
95
96	platform_set_drvdata(pdev, gpio_restart);
97
98	ret = register_restart_handler(&gpio_restart->restart_handler);
99	if (ret) {
100		dev_err(&pdev->dev, "%s: cannot register restart handler, %d\n",
101				__func__, ret);
102		return -ENODEV;
103	}
104
105	return 0;
106}
107
108static void gpio_restart_remove(struct platform_device *pdev)
109{
110	struct gpio_restart *gpio_restart = platform_get_drvdata(pdev);
111	int ret;
112
113	ret = unregister_restart_handler(&gpio_restart->restart_handler);
114	if (ret) {
115		dev_err(&pdev->dev,
116				"%s: cannot unregister restart handler, %d\n",
117				__func__, ret);
118	}
119}
120
121static const struct of_device_id of_gpio_restart_match[] = {
122	{ .compatible = "gpio-restart", },
123	{},
124};
125
126static struct platform_driver gpio_restart_driver = {
127	.probe = gpio_restart_probe,
128	.remove_new = gpio_restart_remove,
129	.driver = {
130		.name = "restart-gpio",
131		.of_match_table = of_gpio_restart_match,
132	},
133};
134
135module_platform_driver(gpio_restart_driver);
136
137MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
138MODULE_DESCRIPTION("GPIO restart driver");
139