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
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
gpio_restart_notify(struct notifier_block * this,unsigned long mode,void * cmd)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
gpio_restart_probe(struct platform_device * pdev)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
gpio_restart_remove(struct platform_device * pdev)108 static 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
121 static const struct of_device_id of_gpio_restart_match[] = {
122 { .compatible = "gpio-restart", },
123 {},
124 };
125
126 static 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
135 module_platform_driver(gpio_restart_driver);
136
137 MODULE_AUTHOR("David Riley <davidriley@chromium.org>");
138 MODULE_DESCRIPTION("GPIO restart driver");
139