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/of_gpio.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/watchdog.h>
  18
  19 #define SOFT_TIMEOUT_MIN        1
  20 #define SOFT_TIMEOUT_DEF        60
  21
  22 enum {
  23         HW_ALGO_TOGGLE,
  24         HW_ALGO_LEVEL,
  25 };
  26
  27 struct gpio_wdt_priv {
  28         int                     gpio;
  29         bool                    active_low;
  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         gpio_set_value_cansleep(priv->gpio, !priv->active_low);
  39
  40         /* Put GPIO back to tristate */
  41         if (priv->hw_algo == HW_ALGO_TOGGLE)
  42                 gpio_direction_input(priv->gpio);
  43 }
  44
  45 static int gpio_wdt_ping(struct watchdog_device *wdd)
  46 {
  47         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  48
  49         switch (priv->hw_algo) {
  50         case HW_ALGO_TOGGLE:
  51                 /* Toggle output pin */
  52                 priv->state = !priv->state;
  53                 gpio_set_value_cansleep(priv->gpio, priv->state);
  54                 break;
  55         case HW_ALGO_LEVEL:
  56                 /* Pulse */
  57                 gpio_set_value_cansleep(priv->gpio, !priv->active_low);
  58                 udelay(1);
  59                 gpio_set_value_cansleep(priv->gpio, priv->active_low);
  60                 break;
  61         }
  62         return 0;
  63 }
  64
  65 static int gpio_wdt_start(struct watchdog_device *wdd)
  66 {
  67         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  68
  69         priv->state = priv->active_low;
  70         gpio_direction_output(priv->gpio, priv->state);
  71
  72         set_bit(WDOG_HW_RUNNING, &wdd->status);
  73
  74         return gpio_wdt_ping(wdd);
  75 }
  76
  77 static int gpio_wdt_stop(struct watchdog_device *wdd)
  78 {
  79         struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  80
  81         if (!priv->always_running) {
  82                 gpio_wdt_disable(priv);
  83         } else {
  84                 set_bit(WDOG_HW_RUNNING, &wdd->status);
  85         }
  86
  87         return 0;
  88 }
  89
  90 static const struct watchdog_info gpio_wdt_ident = {
  91         .options        = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
  92                           WDIOF_SETTIMEOUT,
  93         .identity       = "GPIO Watchdog",
  94 };
  95
  96 static const struct watchdog_ops gpio_wdt_ops = {
  97         .owner          = THIS_MODULE,
  98         .start          = gpio_wdt_start,
  99         .stop           = gpio_wdt_stop,
 100         .ping           = gpio_wdt_ping,
 101 };
 102
 103 static int gpio_wdt_probe(struct platform_device *pdev)
 104 {
 105         struct gpio_wdt_priv *priv;
 106         enum of_gpio_flags flags;
 107         unsigned int hw_margin;
 108         unsigned long f = 0;
 109         const char *algo;
 110         int ret;
 111
 112         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 113         if (!priv)
 114                 return -ENOMEM;
 115
 116         platform_set_drvdata(pdev, priv);
 117
 118         priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
 119         if (!gpio_is_valid(priv->gpio))
 120                 return priv->gpio;
 121
 122         priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
 123
 124         ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
 125         if (ret)
 126                 return ret;
 127         if (!strcmp(algo, "toggle")) {
 128                 priv->hw_algo = HW_ALGO_TOGGLE;
 129                 f = GPIOF_IN;
 130         } else if (!strcmp(algo, "level")) {
 131                 priv->hw_algo = HW_ALGO_LEVEL;
 132                 f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
 133         } else {
 134                 return -EINVAL;
 135         }
 136
 137         ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
 138                                     dev_name(&pdev->dev));
 139         if (ret)
 140                 return ret;
 141
 142         ret = of_property_read_u32(pdev->dev.of_node,
 143                                    "hw_margin_ms", &hw_margin);
 144         if (ret)
 145                 return ret;
 146         /* Disallow values lower than 2 and higher than 65535 ms */
 147         if (hw_margin < 2 || hw_margin > 65535)
 148                 return -EINVAL;
 149
 150         priv->always_running = of_property_read_bool(pdev->dev.of_node,
 151                                                      "always-running");
 152
 153         watchdog_set_drvdata(&priv->wdd, priv);
 154
 155         priv->wdd.info          = &gpio_wdt_ident;
 156         priv->wdd.ops           = &gpio_wdt_ops;
 157         priv->wdd.min_timeout   = SOFT_TIMEOUT_MIN;
 158         priv->wdd.max_hw_heartbeat_ms = hw_margin;
 159         priv->wdd.parent        = &pdev->dev;
 160
 161         if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
 162                 priv->wdd.timeout = SOFT_TIMEOUT_DEF;
 163
 164         watchdog_stop_on_reboot(&priv->wdd);
 165
 166         if (priv->always_running)
 167                 gpio_wdt_start(&priv->wdd);
 168
 169         ret = watchdog_register_device(&priv->wdd);
 170
 171         return ret;
 172 }
 173
 174 static int gpio_wdt_remove(struct platform_device *pdev)
 175 {
 176         struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
 177
 178         watchdog_unregister_device(&priv->wdd);
 179
 180         return 0;
 181 }
 182
 183 static const struct of_device_id gpio_wdt_dt_ids[] = {
 184         { .compatible = "linux,wdt-gpio", },
 185         { }
 186 };
 187 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
 188
 189 static struct platform_driver gpio_wdt_driver = {
 190         .driver = {
 191                 .name           = "gpio-wdt",
 192                 .of_match_table = gpio_wdt_dt_ids,
 193         },
 194         .probe  = gpio_wdt_probe,
 195         .remove = gpio_wdt_remove,
 196 };
 197
 198 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
 199 static int __init gpio_wdt_init(void)
 200 {
 201         return platform_driver_register(&gpio_wdt_driver);
 202 }
 203 arch_initcall(gpio_wdt_init);
 204 #else
 205 module_platform_driver(gpio_wdt_driver);
 206 #endif
 207
 208 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
 209 MODULE_DESCRIPTION("GPIO Watchdog");
 210 MODULE_LICENSE("GPL");