linux/drivers/watchdog/gpio_wdt.c
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   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
  25enum {
  26        HW_ALGO_TOGGLE,
  27        HW_ALGO_LEVEL,
  28};
  29
  30struct gpio_wdt_priv {
  31        int                     gpio;
  32        bool                    active_low;
  33        bool                    state;
  34        unsigned int            hw_algo;
  35        unsigned int            hw_margin;
  36        unsigned long           last_jiffies;
  37        struct notifier_block   notifier;
  38        struct timer_list       timer;
  39        struct watchdog_device  wdd;
  40};
  41
  42static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
  43{
  44        gpio_set_value_cansleep(priv->gpio, !priv->active_low);
  45
  46        /* Put GPIO back to tristate */
  47        if (priv->hw_algo == HW_ALGO_TOGGLE)
  48                gpio_direction_input(priv->gpio);
  49}
  50
  51static int gpio_wdt_start(struct watchdog_device *wdd)
  52{
  53        struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  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        return 0;
  61}
  62
  63static int gpio_wdt_stop(struct watchdog_device *wdd)
  64{
  65        struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  66
  67        mod_timer(&priv->timer, 0);
  68        gpio_wdt_disable(priv);
  69
  70        return 0;
  71}
  72
  73static int gpio_wdt_ping(struct watchdog_device *wdd)
  74{
  75        struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  76
  77        priv->last_jiffies = jiffies;
  78
  79        return 0;
  80}
  81
  82static int gpio_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
  83{
  84        wdd->timeout = t;
  85
  86        return gpio_wdt_ping(wdd);
  87}
  88
  89static void gpio_wdt_hwping(unsigned long data)
  90{
  91        struct watchdog_device *wdd = (struct watchdog_device *)data;
  92        struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  93
  94        if (time_after(jiffies, priv->last_jiffies +
  95                       msecs_to_jiffies(wdd->timeout * 1000))) {
  96                dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
  97                return;
  98        }
  99
 100        /* Restart timer */
 101        mod_timer(&priv->timer, jiffies + priv->hw_margin);
 102
 103        switch (priv->hw_algo) {
 104        case HW_ALGO_TOGGLE:
 105                /* Toggle output pin */
 106                priv->state = !priv->state;
 107                gpio_set_value_cansleep(priv->gpio, priv->state);
 108                break;
 109        case HW_ALGO_LEVEL:
 110                /* Pulse */
 111                gpio_set_value_cansleep(priv->gpio, !priv->active_low);
 112                udelay(1);
 113                gpio_set_value_cansleep(priv->gpio, priv->active_low);
 114                break;
 115        }
 116}
 117
 118static int gpio_wdt_notify_sys(struct notifier_block *nb, unsigned long code,
 119                               void *unused)
 120{
 121        struct gpio_wdt_priv *priv = container_of(nb, struct gpio_wdt_priv,
 122                                                  notifier);
 123
 124        mod_timer(&priv->timer, 0);
 125
 126        switch (code) {
 127        case SYS_HALT:
 128        case SYS_POWER_OFF:
 129                gpio_wdt_disable(priv);
 130                break;
 131        default:
 132                break;
 133        }
 134
 135        return NOTIFY_DONE;
 136}
 137
 138static const struct watchdog_info gpio_wdt_ident = {
 139        .options        = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
 140                          WDIOF_SETTIMEOUT,
 141        .identity       = "GPIO Watchdog",
 142};
 143
 144static const struct watchdog_ops gpio_wdt_ops = {
 145        .owner          = THIS_MODULE,
 146        .start          = gpio_wdt_start,
 147        .stop           = gpio_wdt_stop,
 148        .ping           = gpio_wdt_ping,
 149        .set_timeout    = gpio_wdt_set_timeout,
 150};
 151
 152static int gpio_wdt_probe(struct platform_device *pdev)
 153{
 154        struct gpio_wdt_priv *priv;
 155        enum of_gpio_flags flags;
 156        unsigned int hw_margin;
 157        unsigned long f = 0;
 158        const char *algo;
 159        int ret;
 160
 161        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 162        if (!priv)
 163                return -ENOMEM;
 164
 165        priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
 166        if (!gpio_is_valid(priv->gpio))
 167                return priv->gpio;
 168
 169        priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
 170
 171        ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
 172        if (ret)
 173                return ret;
 174        if (!strncmp(algo, "toggle", 6)) {
 175                priv->hw_algo = HW_ALGO_TOGGLE;
 176                f = GPIOF_IN;
 177        } else if (!strncmp(algo, "level", 5)) {
 178                priv->hw_algo = HW_ALGO_LEVEL;
 179                f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
 180        } else {
 181                return -EINVAL;
 182        }
 183
 184        ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
 185                                    dev_name(&pdev->dev));
 186        if (ret)
 187                return ret;
 188
 189        ret = of_property_read_u32(pdev->dev.of_node,
 190                                   "hw_margin_ms", &hw_margin);
 191        if (ret)
 192                return ret;
 193        /* Disallow values lower than 2 and higher than 65535 ms */
 194        if (hw_margin < 2 || hw_margin > 65535)
 195                return -EINVAL;
 196
 197        /* Use safe value (1/2 of real timeout) */
 198        priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
 199
 200        watchdog_set_drvdata(&priv->wdd, priv);
 201
 202        priv->wdd.info          = &gpio_wdt_ident;
 203        priv->wdd.ops           = &gpio_wdt_ops;
 204        priv->wdd.min_timeout   = SOFT_TIMEOUT_MIN;
 205        priv->wdd.max_timeout   = SOFT_TIMEOUT_MAX;
 206
 207        if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
 208                priv->wdd.timeout = SOFT_TIMEOUT_DEF;
 209
 210        setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
 211
 212        ret = watchdog_register_device(&priv->wdd);
 213        if (ret)
 214                return ret;
 215
 216        priv->notifier.notifier_call = gpio_wdt_notify_sys;
 217        ret = register_reboot_notifier(&priv->notifier);
 218        if (ret)
 219                watchdog_unregister_device(&priv->wdd);
 220
 221        return ret;
 222}
 223
 224static int gpio_wdt_remove(struct platform_device *pdev)
 225{
 226        struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
 227
 228        del_timer_sync(&priv->timer);
 229        unregister_reboot_notifier(&priv->notifier);
 230        watchdog_unregister_device(&priv->wdd);
 231
 232        return 0;
 233}
 234
 235static const struct of_device_id gpio_wdt_dt_ids[] = {
 236        { .compatible = "linux,wdt-gpio", },
 237        { }
 238};
 239MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
 240
 241static struct platform_driver gpio_wdt_driver = {
 242        .driver = {
 243                .name           = "gpio-wdt",
 244                .of_match_table = gpio_wdt_dt_ids,
 245        },
 246        .probe  = gpio_wdt_probe,
 247        .remove = gpio_wdt_remove,
 248};
 249module_platform_driver(gpio_wdt_driver);
 250
 251MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
 252MODULE_DESCRIPTION("GPIO Watchdog");
 253MODULE_LICENSE("GPL");
 254
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