1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Driver for watchdog device controlled through GPIO-line
4 *
5 * Author: 2013, Alexander Shiyan <shc_work@mail.ru>
6 */
7
8 #include <linux/delay.h>
9 #include <linux/err.h>
10 #include <linux/gpio/consumer.h>
11 #include <linux/mod_devicetable.h>
12 #include <linux/module.h>
13 #include <linux/platform_device.h>
14 #include <linux/property.h>
15 #include <linux/watchdog.h>
16
17 static bool nowayout = WATCHDOG_NOWAYOUT;
18 module_param(nowayout, bool, 0);
19 MODULE_PARM_DESC(nowayout,
20 "Watchdog cannot be stopped once started (default="
21 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
22
23 #define SOFT_TIMEOUT_MIN 1
24 #define SOFT_TIMEOUT_DEF 60
25
26 enum {
27 HW_ALGO_TOGGLE,
28 HW_ALGO_LEVEL,
29 };
30
31 struct gpio_wdt_priv {
32 struct gpio_desc *gpiod;
33 bool state;
34 bool always_running;
35 unsigned int hw_algo;
36 struct watchdog_device wdd;
37 };
38
gpio_wdt_disable(struct gpio_wdt_priv * priv)39 static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
40 {
41 /* Eternal ping */
42 gpiod_set_value_cansleep(priv->gpiod, 1);
43
44 /* Put GPIO back to tristate */
45 if (priv->hw_algo == HW_ALGO_TOGGLE)
46 gpiod_direction_input(priv->gpiod);
47 }
48
gpio_wdt_ping(struct watchdog_device * wdd)49 static int gpio_wdt_ping(struct watchdog_device *wdd)
50 {
51 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
52
53 switch (priv->hw_algo) {
54 case HW_ALGO_TOGGLE:
55 /* Toggle output pin */
56 priv->state = !priv->state;
57 gpiod_set_value_cansleep(priv->gpiod, priv->state);
58 break;
59 case HW_ALGO_LEVEL:
60 /* Pulse */
61 gpiod_set_value_cansleep(priv->gpiod, 1);
62 udelay(1);
63 gpiod_set_value_cansleep(priv->gpiod, 0);
64 break;
65 }
66 return 0;
67 }
68
gpio_wdt_start(struct watchdog_device * wdd)69 static int gpio_wdt_start(struct watchdog_device *wdd)
70 {
71 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
72
73 priv->state = 0;
74 gpiod_direction_output(priv->gpiod, priv->state);
75
76 set_bit(WDOG_HW_RUNNING, &wdd->status);
77
78 return gpio_wdt_ping(wdd);
79 }
80
gpio_wdt_stop(struct watchdog_device * wdd)81 static int gpio_wdt_stop(struct watchdog_device *wdd)
82 {
83 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
84
85 if (!priv->always_running) {
86 gpio_wdt_disable(priv);
87 } else {
88 set_bit(WDOG_HW_RUNNING, &wdd->status);
89 }
90
91 return 0;
92 }
93
94 static const struct watchdog_info gpio_wdt_ident = {
95 .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
96 WDIOF_SETTIMEOUT,
97 .identity = "GPIO Watchdog",
98 };
99
100 static const struct watchdog_ops gpio_wdt_ops = {
101 .owner = THIS_MODULE,
102 .start = gpio_wdt_start,
103 .stop = gpio_wdt_stop,
104 .ping = gpio_wdt_ping,
105 };
106
gpio_wdt_probe(struct platform_device * pdev)107 static int gpio_wdt_probe(struct platform_device *pdev)
108 {
109 struct device *dev = &pdev->dev;
110 struct gpio_wdt_priv *priv;
111 enum gpiod_flags gflags;
112 unsigned int hw_margin;
113 const char *algo;
114 int ret;
115
116 priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
117 if (!priv)
118 return -ENOMEM;
119
120 platform_set_drvdata(pdev, priv);
121
122 ret = device_property_read_string(dev, "hw_algo", &algo);
123 if (ret)
124 return ret;
125 if (!strcmp(algo, "toggle")) {
126 priv->hw_algo = HW_ALGO_TOGGLE;
127 gflags = GPIOD_IN;
128 } else if (!strcmp(algo, "level")) {
129 priv->hw_algo = HW_ALGO_LEVEL;
130 gflags = GPIOD_OUT_LOW;
131 } else {
132 return -EINVAL;
133 }
134
135 priv->gpiod = devm_gpiod_get(dev, NULL, gflags);
136 if (IS_ERR(priv->gpiod))
137 return PTR_ERR(priv->gpiod);
138
139 ret = device_property_read_u32(dev, "hw_margin_ms", &hw_margin);
140 if (ret)
141 return ret;
142 /* Disallow values lower than 2 and higher than 65535 ms */
143 if (hw_margin < 2 || hw_margin > 65535)
144 return -EINVAL;
145
146 priv->always_running = device_property_read_bool(dev, "always-running");
147
148 watchdog_set_drvdata(&priv->wdd, priv);
149
150 priv->wdd.info = &gpio_wdt_ident;
151 priv->wdd.ops = &gpio_wdt_ops;
152 priv->wdd.min_timeout = SOFT_TIMEOUT_MIN;
153 priv->wdd.max_hw_heartbeat_ms = hw_margin;
154 priv->wdd.parent = dev;
155 priv->wdd.timeout = SOFT_TIMEOUT_DEF;
156
157 watchdog_init_timeout(&priv->wdd, 0, dev);
158 watchdog_set_nowayout(&priv->wdd, nowayout);
159
160 watchdog_stop_on_reboot(&priv->wdd);
161
162 if (priv->always_running)
163 gpio_wdt_start(&priv->wdd);
164
165 return devm_watchdog_register_device(dev, &priv->wdd);
166 }
167
168 static const struct of_device_id gpio_wdt_dt_ids[] = {
169 { .compatible = "linux,wdt-gpio", },
170 { }
171 };
172 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
173
174 static struct platform_driver gpio_wdt_driver = {
175 .driver = {
176 .name = "gpio-wdt",
177 .of_match_table = gpio_wdt_dt_ids,
178 },
179 .probe = gpio_wdt_probe,
180 };
181
182 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
gpio_wdt_init(void)183 static int __init gpio_wdt_init(void)
184 {
185 return platform_driver_register(&gpio_wdt_driver);
186 }
187 arch_initcall(gpio_wdt_init);
188 #else
189 module_platform_driver(gpio_wdt_driver);
190 #endif
191
192 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
193 MODULE_DESCRIPTION("GPIO Watchdog");
194 MODULE_LICENSE("GPL");
195