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/gpio/consumer.h>
  16 #include <linux/of.h>
  17 #include <linux/platform_device.h>
  18 #include <linux/watchdog.h>
  19
  20 #define SOFT_TIMEOUT_MIN        1
  21 #define SOFT_TIMEOUT_DEF        60
  22
  23 enum {
  24         HW_ALGO_TOGGLE,
  25         HW_ALGO_LEVEL,
  26 };
  27
  28 struct gpio_wdt_priv {
  29         struct gpio_desc        *gpiod;
  30         bool                    state;
  31         bool                    always_running;
  32         unsigned int            hw_algo;
  33         struct watchdog_device  wdd;
  34 };
  35
  36 static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
  37 {
  38         /* Eternal ping */
  39         gpiod_set_value_cansleep(priv->gpiod, 1);
  40
  41         /* Put GPIO back to tristate */
  42         if (priv->hw_algo == HW_ALGO_TOGGLE)
  43                 gpiod_direction_input(priv->gpiod);
  44 }
  45
  46 static int gpio_wdt_ping(struct watchdog_device *wdd)
  47 {
  48         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  49
  50         switch (priv->hw_algo) {
  51         case HW_ALGO_TOGGLE:
  52                 /* Toggle output pin */
  53                 priv->state = !priv->state;
  54                 gpiod_set_value_cansleep(priv->gpiod, priv->state);
  55                 break;
  56         case HW_ALGO_LEVEL:
  57                 /* Pulse */
  58                 gpiod_set_value_cansleep(priv->gpiod, 1);
  59                 udelay(1);
  60                 gpiod_set_value_cansleep(priv->gpiod, 0);
  61                 break;
  62         }
  63         return 0;
  64 }
  65
  66 static int gpio_wdt_start(struct watchdog_device *wdd)
  67 {
  68         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  69
  70         priv->state = 0;
  71         gpiod_direction_output(priv->gpiod, priv->state);
  72
  73         set_bit(WDOG_HW_RUNNING, &wdd->status);
  74
  75         return gpio_wdt_ping(wdd);
  76 }
  77
  78 static int gpio_wdt_stop(struct watchdog_device *wdd)
  79 {
  80         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  81
  82         if (!priv->always_running) {
  83                 gpio_wdt_disable(priv);
  84         } else {
  85                 set_bit(WDOG_HW_RUNNING, &wdd->status);
  86         }
  87
  88         return 0;
  89 }
  90
  91 static const struct watchdog_info gpio_wdt_ident = {
  92         .options        = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
  93                           WDIOF_SETTIMEOUT,
  94         .identity       = "GPIO Watchdog",
  95 };
  96
  97 static const struct watchdog_ops gpio_wdt_ops = {
  98         .owner          = THIS_MODULE,
  99         .start          = gpio_wdt_start,
 100         .stop           = gpio_wdt_stop,
 101         .ping           = gpio_wdt_ping,
 102 };
 103
 104 static int gpio_wdt_probe(struct platform_device *pdev)
 105 {
 106         struct device *dev = &pdev->dev;
 107         struct device_node *np = dev->of_node;
 108         struct gpio_wdt_priv *priv;
 109         enum gpiod_flags gflags;
 110         unsigned int hw_margin;
 111         const char *algo;
 112         int ret;
 113
 114         priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 115         if (!priv)
 116                 return -ENOMEM;
 117
 118         platform_set_drvdata(pdev, priv);
 119
 120         ret = of_property_read_string(np, "hw_algo", &algo);
 121         if (ret)
 122                 return ret;
 123         if (!strcmp(algo, "toggle")) {
 124                 priv->hw_algo = HW_ALGO_TOGGLE;
 125                 gflags = GPIOD_IN;
 126         } else if (!strcmp(algo, "level")) {
 127                 priv->hw_algo = HW_ALGO_LEVEL;
 128                 gflags = GPIOD_OUT_LOW;
 129         } else {
 130                 return -EINVAL;
 131         }
 132
 133         priv->gpiod = devm_gpiod_get(dev, NULL, gflags);
 134         if (IS_ERR(priv->gpiod))
 135                 return PTR_ERR(priv->gpiod);
 136
 137         ret = of_property_read_u32(np,
 138                                    "hw_margin_ms", &hw_margin);
 139         if (ret)
 140                 return ret;
 141         /* Disallow values lower than 2 and higher than 65535 ms */
 142         if (hw_margin < 2 || hw_margin > 65535)
 143                 return -EINVAL;
 144
 145         priv->always_running = of_property_read_bool(np,
 146                                                      "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
 156         if (watchdog_init_timeout(&priv->wdd, 0, dev) < 0)
 157                 priv->wdd.timeout = SOFT_TIMEOUT_DEF;
 158
 159         watchdog_stop_on_reboot(&priv->wdd);
 160
 161         if (priv->always_running)
 162                 gpio_wdt_start(&priv->wdd);
 163
 164         ret = watchdog_register_device(&priv->wdd);
 165
 166         return ret;
 167 }
 168
 169 static int gpio_wdt_remove(struct platform_device *pdev)
 170 {
 171         struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
 172
 173         watchdog_unregister_device(&priv->wdd);
 174
 175         return 0;
 176 }
 177
 178 static const struct of_device_id gpio_wdt_dt_ids[] = {
 179         { .compatible = "linux,wdt-gpio", },
 180         { }
 181 };
 182 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
 183
 184 static struct platform_driver gpio_wdt_driver = {
 185         .driver = {
 186                 .name           = "gpio-wdt",
 187                 .of_match_table = gpio_wdt_dt_ids,
 188         },
 189         .probe  = gpio_wdt_probe,
 190         .remove = gpio_wdt_remove,
 191 };
 192
 193 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
 194 static int __init gpio_wdt_init(void)
 195 {
 196         return platform_driver_register(&gpio_wdt_driver);
 197 }
 198 arch_initcall(gpio_wdt_init);
 199 #else
 200 module_platform_driver(gpio_wdt_driver);
 201 #endif
 202
 203 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
 204 MODULE_DESCRIPTION("GPIO Watchdog");
 205 MODULE_LICENSE("GPL");