drivers/watchdog/gpio_wdt.c

   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
  16 static bool nowayout = WATCHDOG_NOWAYOUT;
  17 module_param(nowayout, bool, 0);
  18 MODULE_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
  25 enum {
  26         HW_ALGO_TOGGLE,
  27         HW_ALGO_LEVEL,
  28 };
  29
  30 struct 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
  38 static 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
  48 static 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
  68 static 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
  80 static 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
  93 static const struct watchdog_info gpio_wdt_ident = {
  94         .options        = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
  95                           WDIOF_SETTIMEOUT,
  96         .identity       = "GPIO Watchdog",
  97 };
  98
  99 static 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
 106 static 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
 170 static const struct of_device_id gpio_wdt_dt_ids[] = {
 171         { .compatible = "linux,wdt-gpio", },
 172         { }
 173 };
 174 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
 175
 176 static 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
 185 static int __init gpio_wdt_init(void)
 186 {
 187         return platform_driver_register(&gpio_wdt_driver);
 188 }
 189 arch_initcall(gpio_wdt_init);
 190 #else
 191 module_platform_driver(gpio_wdt_driver);
 192 #endif
 193
 194 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
 195 MODULE_DESCRIPTION("GPIO Watchdog");
 196 MODULE_LICENSE("GPL");