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                 clear_bit(WDOG_HW_RUNNING, &wdd->status);
  84         }
  85
  86         return 0;
  87 }
  88
  89 static const struct watchdog_info gpio_wdt_ident = {
  90         .options        = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
  91                           WDIOF_SETTIMEOUT,
  92         .identity       = "GPIO Watchdog",
  93 };
  94
  95 static const struct watchdog_ops gpio_wdt_ops = {
  96         .owner          = THIS_MODULE,
  97         .start          = gpio_wdt_start,
  98         .stop           = gpio_wdt_stop,
  99         .ping           = gpio_wdt_ping,
 100 };
 101
 102 static int gpio_wdt_probe(struct platform_device *pdev)
 103 {
 104         struct gpio_wdt_priv *priv;
 105         enum of_gpio_flags flags;
 106         unsigned int hw_margin;
 107         unsigned long f = 0;
 108         const char *algo;
 109         int ret;
 110
 111         priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 112         if (!priv)
 113                 return -ENOMEM;
 114
 115         platform_set_drvdata(pdev, priv);
 116
 117         priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
 118         if (!gpio_is_valid(priv->gpio))
 119                 return priv->gpio;
 120
 121         priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
 122
 123         ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
 124         if (ret)
 125                 return ret;
 126         if (!strcmp(algo, "toggle")) {
 127                 priv->hw_algo = HW_ALGO_TOGGLE;
 128                 f = GPIOF_IN;
 129         } else if (!strcmp(algo, "level")) {
 130                 priv->hw_algo = HW_ALGO_LEVEL;
 131                 f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
 132         } else {
 133                 return -EINVAL;
 134         }
 135
 136         ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
 137                                     dev_name(&pdev->dev));
 138         if (ret)
 139                 return ret;
 140
 141         ret = of_property_read_u32(pdev->dev.of_node,
 142                                    "hw_margin_ms", &hw_margin);
 143         if (ret)
 144                 return ret;
 145         /* Disallow values lower than 2 and higher than 65535 ms */
 146         if (hw_margin < 2 || hw_margin > 65535)
 147                 return -EINVAL;
 148
 149         priv->always_running = of_property_read_bool(pdev->dev.of_node,
 150                                                      "always-running");
 151
 152         watchdog_set_drvdata(&priv->wdd, priv);
 153
 154         priv->wdd.info          = &gpio_wdt_ident;
 155         priv->wdd.ops           = &gpio_wdt_ops;
 156         priv->wdd.min_timeout   = SOFT_TIMEOUT_MIN;
 157         priv->wdd.max_hw_heartbeat_ms = hw_margin;
 158         priv->wdd.parent        = &pdev->dev;
 159
 160         if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
 161                 priv->wdd.timeout = SOFT_TIMEOUT_DEF;
 162
 163         watchdog_stop_on_reboot(&priv->wdd);
 164
 165         if (priv->always_running)
 166                 gpio_wdt_start(&priv->wdd);
 167
 168         ret = watchdog_register_device(&priv->wdd);
 169
 170         return ret;
 171 }
 172
 173 static int gpio_wdt_remove(struct platform_device *pdev)
 174 {
 175         struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
 176
 177         watchdog_unregister_device(&priv->wdd);
 178
 179         return 0;
 180 }
 181
 182 static const struct of_device_id gpio_wdt_dt_ids[] = {
 183         { .compatible = "linux,wdt-gpio", },
 184         { }
 185 };
 186 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
 187
 188 static struct platform_driver gpio_wdt_driver = {
 189         .driver = {
 190                 .name           = "gpio-wdt",
 191                 .of_match_table = gpio_wdt_dt_ids,
 192         },
 193         .probe  = gpio_wdt_probe,
 194         .remove = gpio_wdt_remove,
 195 };
 196
 197 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
 198 static int __init gpio_wdt_init(void)
 199 {
 200         return platform_driver_register(&gpio_wdt_driver);
 201 }
 202 arch_initcall(gpio_wdt_init);
 203 #else
 204 module_platform_driver(gpio_wdt_driver);
 205 #endif
 206
 207 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
 208 MODULE_DESCRIPTION("GPIO Watchdog");
 209 MODULE_LICENSE("GPL");