linux/drivers/watchdog/gpio_wdt.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * Driver for watchdog device controlled through GPIO-line
   4 *
   5 * Author: 2013, Alexander Shiyan <shc_work@mail.ru>
   6 */
   7
   8#include <linux/err.h>
   9#include <linux/delay.h>
  10#include <linux/module.h>
  11#include <linux/gpio/consumer.h>
  12#include <linux/of.h>
  13#include <linux/platform_device.h>
  14#include <linux/watchdog.h>
  15
  16static bool nowayout = WATCHDOG_NOWAYOUT;
  17module_param(nowayout, bool, 0);
  18MODULE_PARM_DESC(nowayout,
  19                "Watchdog cannot be stopped once started (default="
  20                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  21
  22#define SOFT_TIMEOUT_MIN        1
  23#define SOFT_TIMEOUT_DEF        60
  24
  25enum {
  26        HW_ALGO_TOGGLE,
  27        HW_ALGO_LEVEL,
  28};
  29
  30struct gpio_wdt_priv {
  31        struct gpio_desc        *gpiod;
  32        bool                    state;
  33        bool                    always_running;
  34        unsigned int            hw_algo;
  35        struct watchdog_device  wdd;
  36};
  37
  38static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
  39{
  40        /* Eternal ping */
  41        gpiod_set_value_cansleep(priv->gpiod, 1);
  42
  43        /* Put GPIO back to tristate */
  44        if (priv->hw_algo == HW_ALGO_TOGGLE)
  45                gpiod_direction_input(priv->gpiod);
  46}
  47
  48static int gpio_wdt_ping(struct watchdog_device *wdd)
  49{
  50        struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  51
  52        switch (priv->hw_algo) {
  53        case HW_ALGO_TOGGLE:
  54                /* Toggle output pin */
  55                priv->state = !priv->state;
  56                gpiod_set_value_cansleep(priv->gpiod, priv->state);
  57                break;
  58        case HW_ALGO_LEVEL:
  59                /* Pulse */
  60                gpiod_set_value_cansleep(priv->gpiod, 1);
  61                udelay(1);
  62                gpiod_set_value_cansleep(priv->gpiod, 0);
  63                break;
  64        }
  65        return 0;
  66}
  67
  68static int gpio_wdt_start(struct watchdog_device *wdd)
  69{
  70        struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  71
  72        priv->state = 0;
  73        gpiod_direction_output(priv->gpiod, priv->state);
  74
  75        set_bit(WDOG_HW_RUNNING, &wdd->status);
  76
  77        return gpio_wdt_ping(wdd);
  78}
  79
  80static int gpio_wdt_stop(struct watchdog_device *wdd)
  81{
  82        struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
  83
  84        if (!priv->always_running) {
  85                gpio_wdt_disable(priv);
  86        } else {
  87                set_bit(WDOG_HW_RUNNING, &wdd->status);
  88        }
  89
  90        return 0;
  91}
  92
  93static const struct watchdog_info gpio_wdt_ident = {
  94        .options        = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
  95                          WDIOF_SETTIMEOUT,
  96        .identity       = "GPIO Watchdog",
  97};
  98
  99static const struct watchdog_ops gpio_wdt_ops = {
 100        .owner          = THIS_MODULE,
 101        .start          = gpio_wdt_start,
 102        .stop           = gpio_wdt_stop,
 103        .ping           = gpio_wdt_ping,
 104};
 105
 106static int gpio_wdt_probe(struct platform_device *pdev)
 107{
 108        struct device *dev = &pdev->dev;
 109        struct device_node *np = dev->of_node;
 110        struct gpio_wdt_priv *priv;
 111        enum gpiod_flags gflags;
 112        unsigned int hw_margin;
 113        const char *algo;
 114        int ret;
 115
 116        priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 117        if (!priv)
 118                return -ENOMEM;
 119
 120        platform_set_drvdata(pdev, priv);
 121
 122        ret = of_property_read_string(np, "hw_algo", &algo);
 123        if (ret)
 124                return ret;
 125        if (!strcmp(algo, "toggle")) {
 126                priv->hw_algo = HW_ALGO_TOGGLE;
 127                gflags = GPIOD_IN;
 128        } else if (!strcmp(algo, "level")) {
 129                priv->hw_algo = HW_ALGO_LEVEL;
 130                gflags = GPIOD_OUT_LOW;
 131        } else {
 132                return -EINVAL;
 133        }
 134
 135        priv->gpiod = devm_gpiod_get(dev, NULL, gflags);
 136        if (IS_ERR(priv->gpiod))
 137                return PTR_ERR(priv->gpiod);
 138
 139        ret = of_property_read_u32(np,
 140                                   "hw_margin_ms", &hw_margin);
 141        if (ret)
 142                return ret;
 143        /* Disallow values lower than 2 and higher than 65535 ms */
 144        if (hw_margin < 2 || hw_margin > 65535)
 145                return -EINVAL;
 146
 147        priv->always_running = of_property_read_bool(np,
 148                                                     "always-running");
 149
 150        watchdog_set_drvdata(&priv->wdd, priv);
 151
 152        priv->wdd.info          = &gpio_wdt_ident;
 153        priv->wdd.ops           = &gpio_wdt_ops;
 154        priv->wdd.min_timeout   = SOFT_TIMEOUT_MIN;
 155        priv->wdd.max_hw_heartbeat_ms = hw_margin;
 156        priv->wdd.parent        = dev;
 157        priv->wdd.timeout       = SOFT_TIMEOUT_DEF;
 158
 159        watchdog_init_timeout(&priv->wdd, 0, dev);
 160        watchdog_set_nowayout(&priv->wdd, nowayout);
 161
 162        watchdog_stop_on_reboot(&priv->wdd);
 163
 164        if (priv->always_running)
 165                gpio_wdt_start(&priv->wdd);
 166
 167        return devm_watchdog_register_device(dev, &priv->wdd);
 168}
 169
 170static const struct of_device_id gpio_wdt_dt_ids[] = {
 171        { .compatible = "linux,wdt-gpio", },
 172        { }
 173};
 174MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
 175
 176static struct platform_driver gpio_wdt_driver = {
 177        .driver = {
 178                .name           = "gpio-wdt",
 179                .of_match_table = gpio_wdt_dt_ids,
 180        },
 181        .probe  = gpio_wdt_probe,
 182};
 183
 184#ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
 185static int __init gpio_wdt_init(void)
 186{
 187        return platform_driver_register(&gpio_wdt_driver);
 188}
 189arch_initcall(gpio_wdt_init);
 190#else
 191module_platform_driver(gpio_wdt_driver);
 192#endif
 193
 194MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
 195MODULE_DESCRIPTION("GPIO Watchdog");
 196MODULE_LICENSE("GPL");
 197