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	u32 active_delay_ms;
21	u32 inactive_delay_ms;
22	u32 wait_delay_ms;
23};
24
25static int gpio_restart_notify(struct sys_off_data *data)
26{
27	struct gpio_restart *gpio_restart = data->cb_data;
28
29	/* drive it active, also inactive->active edge */
30	gpiod_direction_output(gpio_restart->reset_gpio, 1);
31	mdelay(gpio_restart->active_delay_ms);
32
33	/* drive inactive, also active->inactive edge */
34	gpiod_set_value(gpio_restart->reset_gpio, 0);
35	mdelay(gpio_restart->inactive_delay_ms);
36
37	/* drive it active, also inactive->active edge */
38	gpiod_set_value(gpio_restart->reset_gpio, 1);
39
40	/* give it some time */
41	mdelay(gpio_restart->wait_delay_ms);
42
43	WARN_ON(1);
44
45	return NOTIFY_DONE;
46}
47
48static int gpio_restart_probe(struct platform_device *pdev)
49{
50	struct gpio_restart *gpio_restart;
51	bool open_source = false;
52	int priority = 129;
53	u32 property;
54	int ret;
55
56	gpio_restart = devm_kzalloc(&pdev->dev, sizeof(*gpio_restart),
57			GFP_KERNEL);
58	if (!gpio_restart)
59		return -ENOMEM;
60
61	open_source = of_property_read_bool(pdev->dev.of_node, "open-source");
62
63	gpio_restart->reset_gpio = devm_gpiod_get(&pdev->dev, NULL,
64			open_source ? GPIOD_IN : GPIOD_OUT_LOW);
65	ret = PTR_ERR_OR_ZERO(gpio_restart->reset_gpio);
66	if (ret) {
67		if (ret != -EPROBE_DEFER)
68			dev_err(&pdev->dev, "Could not get reset GPIO\n");
69		return ret;
70	}
71
72	gpio_restart->active_delay_ms = 100;
73	gpio_restart->inactive_delay_ms = 100;
74	gpio_restart->wait_delay_ms = 3000;
75
76	ret = of_property_read_u32(pdev->dev.of_node, "priority", &property);
77	if (!ret) {
78		if (property > 255)
79			dev_err(&pdev->dev, "Invalid priority property: %u\n",
80					property);
81		else
82			priority = property;
83	}
84
85	of_property_read_u32(pdev->dev.of_node, "active-delay",
86			&gpio_restart->active_delay_ms);
87	of_property_read_u32(pdev->dev.of_node, "inactive-delay",
88			&gpio_restart->inactive_delay_ms);
89	of_property_read_u32(pdev->dev.of_node, "wait-delay",
90			&gpio_restart->wait_delay_ms);
91
92	ret = devm_register_sys_off_handler(&pdev->dev,
93					    SYS_OFF_MODE_RESTART,
94					    priority,
95					    gpio_restart_notify,
96					    gpio_restart);
97	if (ret) {
98		dev_err(&pdev->dev, "%s: cannot register restart handler, %d\n",
99				__func__, ret);
100		return -ENODEV;
101	}
102
103	return 0;
104}
105
106static const struct of_device_id of_gpio_restart_match[] = {
107	{ .compatible = "gpio-restart", },
108	{},
109};
110
111static struct platform_driver gpio_restart_driver = {
112	.probe = gpio_restart_probe,
113	.driver = {
114		.name = "restart-gpio",
115		.of_match_table = of_gpio_restart_match,
116	},
117};
118
119module_platform_driver(gpio_restart_driver);
120
121MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
122MODULE_DESCRIPTION("GPIO restart driver");
123