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Linux/drivers/watchdog/gpio_wdt.c

  1 /*
  2  * Driver for watchdog device controlled through GPIO-line
  3  *
  4  * Author: 2013, Alexander Shiyan <shc_work@mail.ru>
  5  *
  6  * This program is free software; you can redistribute it and/or modify
  7  * it under the terms of the GNU General Public License as published by
  8  * the Free Software Foundation; either version 2 of the License, or
  9  * (at your option) any later version.
 10  */
 11 
 12 #include <linux/err.h>
 13 #include <linux/delay.h>
 14 #include <linux/module.h>
 15 #include <linux/notifier.h>
 16 #include <linux/of_gpio.h>
 17 #include <linux/platform_device.h>
 18 #include <linux/reboot.h>
 19 #include <linux/watchdog.h>
 20 
 21 #define SOFT_TIMEOUT_MIN        1
 22 #define SOFT_TIMEOUT_DEF        60
 23 #define SOFT_TIMEOUT_MAX        0xffff
 24 
 25 enum {
 26         HW_ALGO_TOGGLE,
 27         HW_ALGO_LEVEL,
 28 };
 29 
 30 struct gpio_wdt_priv {
 31         int                     gpio;
 32         bool                    active_low;
 33         bool                    state;
 34         bool                    always_running;
 35         bool                    armed;
 36         unsigned int            hw_algo;
 37         unsigned int            hw_margin;
 38         unsigned long           last_jiffies;
 39         struct notifier_block   notifier;
 40         struct timer_list       timer;
 41         struct watchdog_device  wdd;
 42 };
 43 
 44 static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
 45 {
 46         gpio_set_value_cansleep(priv->gpio, !priv->active_low);
 47 
 48         /* Put GPIO back to tristate */
 49         if (priv->hw_algo == HW_ALGO_TOGGLE)
 50                 gpio_direction_input(priv->gpio);
 51 }
 52 
 53 static void gpio_wdt_start_impl(struct gpio_wdt_priv *priv)
 54 {
 55         priv->state = priv->active_low;
 56         gpio_direction_output(priv->gpio, priv->state);
 57         priv->last_jiffies = jiffies;
 58         mod_timer(&priv->timer, priv->last_jiffies + priv->hw_margin);
 59 }
 60 
 61 static int gpio_wdt_start(struct watchdog_device *wdd)
 62 {
 63         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
 64 
 65         gpio_wdt_start_impl(priv);
 66         priv->armed = true;
 67 
 68         return 0;
 69 }
 70 
 71 static int gpio_wdt_stop(struct watchdog_device *wdd)
 72 {
 73         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
 74 
 75         priv->armed = false;
 76         if (!priv->always_running) {
 77                 mod_timer(&priv->timer, 0);
 78                 gpio_wdt_disable(priv);
 79         }
 80 
 81         return 0;
 82 }
 83 
 84 static int gpio_wdt_ping(struct watchdog_device *wdd)
 85 {
 86         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
 87 
 88         priv->last_jiffies = jiffies;
 89 
 90         return 0;
 91 }
 92 
 93 static int gpio_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
 94 {
 95         wdd->timeout = t;
 96 
 97         return gpio_wdt_ping(wdd);
 98 }
 99 
100 static void gpio_wdt_hwping(unsigned long data)
101 {
102         struct watchdog_device *wdd = (struct watchdog_device *)data;
103         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
104 
105         if (priv->armed && time_after(jiffies, priv->last_jiffies +
106                                       msecs_to_jiffies(wdd->timeout * 1000))) {
107                 dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
108                 return;
109         }
110 
111         /* Restart timer */
112         mod_timer(&priv->timer, jiffies + priv->hw_margin);
113 
114         switch (priv->hw_algo) {
115         case HW_ALGO_TOGGLE:
116                 /* Toggle output pin */
117                 priv->state = !priv->state;
118                 gpio_set_value_cansleep(priv->gpio, priv->state);
119                 break;
120         case HW_ALGO_LEVEL:
121                 /* Pulse */
122                 gpio_set_value_cansleep(priv->gpio, !priv->active_low);
123                 udelay(1);
124                 gpio_set_value_cansleep(priv->gpio, priv->active_low);
125                 break;
126         }
127 }
128 
129 static int gpio_wdt_notify_sys(struct notifier_block *nb, unsigned long code,
130                                void *unused)
131 {
132         struct gpio_wdt_priv *priv = container_of(nb, struct gpio_wdt_priv,
133                                                   notifier);
134 
135         mod_timer(&priv->timer, 0);
136 
137         switch (code) {
138         case SYS_HALT:
139         case SYS_POWER_OFF:
140                 gpio_wdt_disable(priv);
141                 break;
142         default:
143                 break;
144         }
145 
146         return NOTIFY_DONE;
147 }
148 
149 static const struct watchdog_info gpio_wdt_ident = {
150         .options        = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
151                           WDIOF_SETTIMEOUT,
152         .identity       = "GPIO Watchdog",
153 };
154 
155 static const struct watchdog_ops gpio_wdt_ops = {
156         .owner          = THIS_MODULE,
157         .start          = gpio_wdt_start,
158         .stop           = gpio_wdt_stop,
159         .ping           = gpio_wdt_ping,
160         .set_timeout    = gpio_wdt_set_timeout,
161 };
162 
163 static int gpio_wdt_probe(struct platform_device *pdev)
164 {
165         struct gpio_wdt_priv *priv;
166         enum of_gpio_flags flags;
167         unsigned int hw_margin;
168         unsigned long f = 0;
169         const char *algo;
170         int ret;
171 
172         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
173         if (!priv)
174                 return -ENOMEM;
175 
176         priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
177         if (!gpio_is_valid(priv->gpio))
178                 return priv->gpio;
179 
180         priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
181 
182         ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
183         if (ret)
184                 return ret;
185         if (!strncmp(algo, "toggle", 6)) {
186                 priv->hw_algo = HW_ALGO_TOGGLE;
187                 f = GPIOF_IN;
188         } else if (!strncmp(algo, "level", 5)) {
189                 priv->hw_algo = HW_ALGO_LEVEL;
190                 f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
191         } else {
192                 return -EINVAL;
193         }
194 
195         ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
196                                     dev_name(&pdev->dev));
197         if (ret)
198                 return ret;
199 
200         ret = of_property_read_u32(pdev->dev.of_node,
201                                    "hw_margin_ms", &hw_margin);
202         if (ret)
203                 return ret;
204         /* Disallow values lower than 2 and higher than 65535 ms */
205         if (hw_margin < 2 || hw_margin > 65535)
206                 return -EINVAL;
207 
208         /* Use safe value (1/2 of real timeout) */
209         priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
210 
211         priv->always_running = of_property_read_bool(pdev->dev.of_node,
212                                                      "always-running");
213 
214         watchdog_set_drvdata(&priv->wdd, priv);
215 
216         priv->wdd.info          = &gpio_wdt_ident;
217         priv->wdd.ops           = &gpio_wdt_ops;
218         priv->wdd.min_timeout   = SOFT_TIMEOUT_MIN;
219         priv->wdd.max_timeout   = SOFT_TIMEOUT_MAX;
220 
221         if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
222                 priv->wdd.timeout = SOFT_TIMEOUT_DEF;
223 
224         setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
225 
226         ret = watchdog_register_device(&priv->wdd);
227         if (ret)
228                 return ret;
229 
230         priv->notifier.notifier_call = gpio_wdt_notify_sys;
231         ret = register_reboot_notifier(&priv->notifier);
232         if (ret)
233                 goto error_unregister;
234 
235         if (priv->always_running)
236                 gpio_wdt_start_impl(priv);
237 
238         return 0;
239 
240 error_unregister:
241         watchdog_unregister_device(&priv->wdd);
242         return ret;
243 }
244 
245 static int gpio_wdt_remove(struct platform_device *pdev)
246 {
247         struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
248 
249         del_timer_sync(&priv->timer);
250         unregister_reboot_notifier(&priv->notifier);
251         watchdog_unregister_device(&priv->wdd);
252 
253         return 0;
254 }
255 
256 static const struct of_device_id gpio_wdt_dt_ids[] = {
257         { .compatible = "linux,wdt-gpio", },
258         { }
259 };
260 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
261 
262 static struct platform_driver gpio_wdt_driver = {
263         .driver = {
264                 .name           = "gpio-wdt",
265                 .of_match_table = gpio_wdt_dt_ids,
266         },
267         .probe  = gpio_wdt_probe,
268         .remove = gpio_wdt_remove,
269 };
270 module_platform_driver(gpio_wdt_driver);
271 
272 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
273 MODULE_DESCRIPTION("GPIO Watchdog");
274 MODULE_LICENSE("GPL");
275 

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