drivers/watchdog/gpio_wdt.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * Driver for watchdog device controlled through GPIO-line
0004  *
0005  * Author: 2013, Alexander Shiyan <shc_work@mail.ru>
0006  */
0007
0008 #include <linux/err.h>
0009 #include <linux/delay.h>
0010 #include <linux/module.h>
0011 #include <linux/gpio/consumer.h>
0012 #include <linux/of.h>
0013 #include <linux/platform_device.h>
0014 #include <linux/watchdog.h>
0015
0016 static bool nowayout = WATCHDOG_NOWAYOUT;
0017 module_param(nowayout, bool, 0);
0018 MODULE_PARM_DESC(nowayout,
0019         "Watchdog cannot be stopped once started (default="
0020                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
0021
0022 #define SOFT_TIMEOUT_MIN    1
0023 #define SOFT_TIMEOUT_DEF    60
0024
0025 enum {
0026     HW_ALGO_TOGGLE,
0027     HW_ALGO_LEVEL,
0028 };
0029
0030 struct gpio_wdt_priv {
0031     struct gpio_desc    *gpiod;
0032     bool            state;
0033     bool            always_running;
0034     unsigned int        hw_algo;
0035     struct watchdog_device  wdd;
0036 };
0037
0038 static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
0039 {
0040     /* Eternal ping */
0041     gpiod_set_value_cansleep(priv->gpiod, 1);
0042
0043     /* Put GPIO back to tristate */
0044     if (priv->hw_algo == HW_ALGO_TOGGLE)
0045         gpiod_direction_input(priv->gpiod);
0046 }
0047
0048 static int gpio_wdt_ping(struct watchdog_device *wdd)
0049 {
0050     struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
0051
0052     switch (priv->hw_algo) {
0053     case HW_ALGO_TOGGLE:
0054         /* Toggle output pin */
0055         priv->state = !priv->state;
0056         gpiod_set_value_cansleep(priv->gpiod, priv->state);
0057         break;
0058     case HW_ALGO_LEVEL:
0059         /* Pulse */
0060         gpiod_set_value_cansleep(priv->gpiod, 1);
0061         udelay(1);
0062         gpiod_set_value_cansleep(priv->gpiod, 0);
0063         break;
0064     }
0065     return 0;
0066 }
0067
0068 static int gpio_wdt_start(struct watchdog_device *wdd)
0069 {
0070     struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
0071
0072     priv->state = 0;
0073     gpiod_direction_output(priv->gpiod, priv->state);
0074
0075     set_bit(WDOG_HW_RUNNING, &wdd->status);
0076
0077     return gpio_wdt_ping(wdd);
0078 }
0079
0080 static int gpio_wdt_stop(struct watchdog_device *wdd)
0081 {
0082     struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
0083
0084     if (!priv->always_running) {
0085         gpio_wdt_disable(priv);
0086     } else {
0087         set_bit(WDOG_HW_RUNNING, &wdd->status);
0088     }
0089
0090     return 0;
0091 }
0092
0093 static const struct watchdog_info gpio_wdt_ident = {
0094     .options    = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
0095               WDIOF_SETTIMEOUT,
0096     .identity   = "GPIO Watchdog",
0097 };
0098
0099 static const struct watchdog_ops gpio_wdt_ops = {
0100     .owner      = THIS_MODULE,
0101     .start      = gpio_wdt_start,
0102     .stop       = gpio_wdt_stop,
0103     .ping       = gpio_wdt_ping,
0104 };
0105
0106 static int gpio_wdt_probe(struct platform_device *pdev)
0107 {
0108     struct device *dev = &pdev->dev;
0109     struct device_node *np = dev->of_node;
0110     struct gpio_wdt_priv *priv;
0111     enum gpiod_flags gflags;
0112     unsigned int hw_margin;
0113     const char *algo;
0114     int ret;
0115
0116     priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
0117     if (!priv)
0118         return -ENOMEM;
0119
0120     platform_set_drvdata(pdev, priv);
0121
0122     ret = of_property_read_string(np, "hw_algo", &algo);
0123     if (ret)
0124         return ret;
0125     if (!strcmp(algo, "toggle")) {
0126         priv->hw_algo = HW_ALGO_TOGGLE;
0127         gflags = GPIOD_IN;
0128     } else if (!strcmp(algo, "level")) {
0129         priv->hw_algo = HW_ALGO_LEVEL;
0130         gflags = GPIOD_OUT_LOW;
0131     } else {
0132         return -EINVAL;
0133     }
0134
0135     priv->gpiod = devm_gpiod_get(dev, NULL, gflags);
0136     if (IS_ERR(priv->gpiod))
0137         return PTR_ERR(priv->gpiod);
0138
0139     ret = of_property_read_u32(np,
0140                    "hw_margin_ms", &hw_margin);
0141     if (ret)
0142         return ret;
0143     /* Disallow values lower than 2 and higher than 65535 ms */
0144     if (hw_margin < 2 || hw_margin > 65535)
0145         return -EINVAL;
0146
0147     priv->always_running = of_property_read_bool(np,
0148                              "always-running");
0149
0150     watchdog_set_drvdata(&priv->wdd, priv);
0151
0152     priv->wdd.info      = &gpio_wdt_ident;
0153     priv->wdd.ops       = &gpio_wdt_ops;
0154     priv->wdd.min_timeout   = SOFT_TIMEOUT_MIN;
0155     priv->wdd.max_hw_heartbeat_ms = hw_margin;
0156     priv->wdd.parent    = dev;
0157     priv->wdd.timeout   = SOFT_TIMEOUT_DEF;
0158
0159     watchdog_init_timeout(&priv->wdd, 0, dev);
0160     watchdog_set_nowayout(&priv->wdd, nowayout);
0161
0162     watchdog_stop_on_reboot(&priv->wdd);
0163
0164     if (priv->always_running)
0165         gpio_wdt_start(&priv->wdd);
0166
0167     return devm_watchdog_register_device(dev, &priv->wdd);
0168 }
0169
0170 static const struct of_device_id gpio_wdt_dt_ids[] = {
0171     { .compatible = "linux,wdt-gpio", },
0172     { }
0173 };
0174 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
0175
0176 static struct platform_driver gpio_wdt_driver = {
0177     .driver = {
0178         .name       = "gpio-wdt",
0179         .of_match_table = gpio_wdt_dt_ids,
0180     },
0181     .probe  = gpio_wdt_probe,
0182 };
0183
0184 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
0185 static int __init gpio_wdt_init(void)
0186 {
0187     return platform_driver_register(&gpio_wdt_driver);
0188 }
0189 arch_initcall(gpio_wdt_init);
0190 #else
0191 module_platform_driver(gpio_wdt_driver);
0192 #endif
0193
0194 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
0195 MODULE_DESCRIPTION("GPIO Watchdog");
0196 MODULE_LICENSE("GPL");