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(desc: gpio_restart->reset_gpio, value: 1);
34 mdelay(gpio_restart->active_delay_ms);
35
36 /* drive inactive, also active->inactive edge */
37 gpiod_set_value(desc: gpio_restart->reset_gpio, value: 0);
38 mdelay(gpio_restart->inactive_delay_ms);
39
40 /* drive it active, also inactive->active edge */
41 gpiod_set_value(desc: gpio_restart->reset_gpio, value: 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(dev: &pdev->dev, size: sizeof(*gpio_restart),
59 GFP_KERNEL);
60 if (!gpio_restart)
61 return -ENOMEM;
62
63 open_source = of_property_read_bool(np: pdev->dev.of_node, propname: "open-source");
64
65 gpio_restart->reset_gpio = devm_gpiod_get(dev: &pdev->dev, NULL,
66 flags: open_source ? GPIOD_IN : GPIOD_OUT_LOW);
67 ret = PTR_ERR_OR_ZERO(ptr: 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(np: pdev->dev.of_node, propname: "priority", out_value: &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(np: pdev->dev.of_node, propname: "active-delay",
90 out_value: &gpio_restart->active_delay_ms);
91 of_property_read_u32(np: pdev->dev.of_node, propname: "inactive-delay",
92 out_value: &gpio_restart->inactive_delay_ms);
93 of_property_read_u32(np: pdev->dev.of_node, propname: "wait-delay",
94 out_value: &gpio_restart->wait_delay_ms);
95
96 platform_set_drvdata(pdev, data: 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

source code of linux/drivers/power/reset/gpio-restart.c