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/of_platform.h>
16 #include <linux/module.h>
17 
18 struct 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 
26 static 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 
51 static 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 
108 static int 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 		return -ENODEV;
119 	}
120 
121 	return 0;
122 }
123 
124 static const struct of_device_id of_gpio_restart_match[] = {
125 	{ .compatible = "gpio-restart", },
126 	{},
127 };
128 
129 static struct platform_driver gpio_restart_driver = {
130 	.probe = gpio_restart_probe,
131 	.remove = gpio_restart_remove,
132 	.driver = {
133 		.name = "restart-gpio",
134 		.of_match_table = of_gpio_restart_match,
135 	},
136 };
137 
138 module_platform_driver(gpio_restart_driver);
139 
140 MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
141 MODULE_DESCRIPTION("GPIO restart driver");
142 MODULE_LICENSE("GPL");
143