1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Driver for watchdog device controlled through GPIO-line
5 * Author: 2013, Alexander Shiyan <shc_work@mail.ru>
9 #include <linux/delay.h>
10 #include <linux/module.h>
11 #include <linux/gpio/consumer.h>
13 #include <linux/platform_device.h>
14 #include <linux/watchdog.h>
16 #define SOFT_TIMEOUT_MIN 1
17 #define SOFT_TIMEOUT_DEF 60
24 struct gpio_wdt_priv {
25 struct gpio_desc *gpiod;
29 struct watchdog_device wdd;
32 static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
35 gpiod_set_value_cansleep(priv->gpiod, 1);
37 /* Put GPIO back to tristate */
38 if (priv->hw_algo == HW_ALGO_TOGGLE)
39 gpiod_direction_input(priv->gpiod);
42 static int gpio_wdt_ping(struct watchdog_device *wdd)
44 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
46 switch (priv->hw_algo) {
48 /* Toggle output pin */
49 priv->state = !priv->state;
50 gpiod_set_value_cansleep(priv->gpiod, priv->state);
54 gpiod_set_value_cansleep(priv->gpiod, 1);
56 gpiod_set_value_cansleep(priv->gpiod, 0);
62 static int gpio_wdt_start(struct watchdog_device *wdd)
64 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
67 gpiod_direction_output(priv->gpiod, priv->state);
69 set_bit(WDOG_HW_RUNNING, &wdd->status);
71 return gpio_wdt_ping(wdd);
74 static int gpio_wdt_stop(struct watchdog_device *wdd)
76 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
78 if (!priv->always_running) {
79 gpio_wdt_disable(priv);
81 set_bit(WDOG_HW_RUNNING, &wdd->status);
87 static const struct watchdog_info gpio_wdt_ident = {
88 .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
90 .identity = "GPIO Watchdog",
93 static const struct watchdog_ops gpio_wdt_ops = {
95 .start = gpio_wdt_start,
96 .stop = gpio_wdt_stop,
97 .ping = gpio_wdt_ping,
100 static int gpio_wdt_probe(struct platform_device *pdev)
102 struct device *dev = &pdev->dev;
103 struct device_node *np = dev->of_node;
104 struct gpio_wdt_priv *priv;
105 enum gpiod_flags gflags;
106 unsigned int hw_margin;
110 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
114 platform_set_drvdata(pdev, priv);
116 ret = of_property_read_string(np, "hw_algo", &algo);
119 if (!strcmp(algo, "toggle")) {
120 priv->hw_algo = HW_ALGO_TOGGLE;
122 } else if (!strcmp(algo, "level")) {
123 priv->hw_algo = HW_ALGO_LEVEL;
124 gflags = GPIOD_OUT_LOW;
129 priv->gpiod = devm_gpiod_get(dev, NULL, gflags);
130 if (IS_ERR(priv->gpiod))
131 return PTR_ERR(priv->gpiod);
133 ret = of_property_read_u32(np,
134 "hw_margin_ms", &hw_margin);
137 /* Disallow values lower than 2 and higher than 65535 ms */
138 if (hw_margin < 2 || hw_margin > 65535)
141 priv->always_running = of_property_read_bool(np,
144 watchdog_set_drvdata(&priv->wdd, priv);
146 priv->wdd.info = &gpio_wdt_ident;
147 priv->wdd.ops = &gpio_wdt_ops;
148 priv->wdd.min_timeout = SOFT_TIMEOUT_MIN;
149 priv->wdd.max_hw_heartbeat_ms = hw_margin;
150 priv->wdd.parent = dev;
151 priv->wdd.timeout = SOFT_TIMEOUT_DEF;
153 watchdog_init_timeout(&priv->wdd, 0, dev);
155 watchdog_stop_on_reboot(&priv->wdd);
157 if (priv->always_running)
158 gpio_wdt_start(&priv->wdd);
160 return devm_watchdog_register_device(dev, &priv->wdd);
163 static const struct of_device_id gpio_wdt_dt_ids[] = {
164 { .compatible = "linux,wdt-gpio", },
167 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
169 static struct platform_driver gpio_wdt_driver = {
172 .of_match_table = gpio_wdt_dt_ids,
174 .probe = gpio_wdt_probe,
177 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
178 static int __init gpio_wdt_init(void)
180 return platform_driver_register(&gpio_wdt_driver);
182 arch_initcall(gpio_wdt_init);
184 module_platform_driver(gpio_wdt_driver);
187 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
188 MODULE_DESCRIPTION("GPIO Watchdog");
189 MODULE_LICENSE("GPL");