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/delay.h> 9 #include <linux/err.h> 10 #include <linux/gpio/consumer.h> 11 #include <linux/mod_devicetable.h> 12 #include <linux/module.h> 13 #include <linux/platform_device.h> 14 #include <linux/property.h> 15 #include <linux/watchdog.h> 16 17 static bool nowayout = WATCHDOG_NOWAYOUT; 18 module_param(nowayout, bool, 0); 19 MODULE_PARM_DESC(nowayout, 20 "Watchdog cannot be stopped once started (default=" 21 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 22 23 #define SOFT_TIMEOUT_MIN 1 24 #define SOFT_TIMEOUT_DEF 60 25 26 enum { 27 HW_ALGO_TOGGLE, 28 HW_ALGO_LEVEL, 29 }; 30 31 struct gpio_wdt_priv { 32 struct gpio_desc *gpiod; 33 bool state; 34 bool always_running; 35 unsigned int hw_algo; 36 struct watchdog_device wdd; 37 }; 38 39 static void gpio_wdt_disable(struct gpio_wdt_priv *priv) 40 { 41 /* Eternal ping */ 42 gpiod_set_value_cansleep(priv->gpiod, 1); 43 44 /* Put GPIO back to tristate */ 45 if (priv->hw_algo == HW_ALGO_TOGGLE) 46 gpiod_direction_input(priv->gpiod); 47 } 48 49 static int gpio_wdt_ping(struct watchdog_device *wdd) 50 { 51 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd); 52 53 switch (priv->hw_algo) { 54 case HW_ALGO_TOGGLE: 55 /* Toggle output pin */ 56 priv->state = !priv->state; 57 gpiod_set_value_cansleep(priv->gpiod, priv->state); 58 break; 59 case HW_ALGO_LEVEL: 60 /* Pulse */ 61 gpiod_set_value_cansleep(priv->gpiod, 1); 62 udelay(1); 63 gpiod_set_value_cansleep(priv->gpiod, 0); 64 break; 65 } 66 return 0; 67 } 68 69 static int gpio_wdt_start(struct watchdog_device *wdd) 70 { 71 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd); 72 73 priv->state = 0; 74 gpiod_direction_output(priv->gpiod, priv->state); 75 76 set_bit(WDOG_HW_RUNNING, &wdd->status); 77 78 return gpio_wdt_ping(wdd); 79 } 80 81 static int gpio_wdt_stop(struct watchdog_device *wdd) 82 { 83 struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd); 84 85 if (!priv->always_running) { 86 gpio_wdt_disable(priv); 87 } else { 88 set_bit(WDOG_HW_RUNNING, &wdd->status); 89 } 90 91 return 0; 92 } 93 94 static const struct watchdog_info gpio_wdt_ident = { 95 .options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | 96 WDIOF_SETTIMEOUT, 97 .identity = "GPIO Watchdog", 98 }; 99 100 static const struct watchdog_ops gpio_wdt_ops = { 101 .owner = THIS_MODULE, 102 .start = gpio_wdt_start, 103 .stop = gpio_wdt_stop, 104 .ping = gpio_wdt_ping, 105 }; 106 107 static int gpio_wdt_probe(struct platform_device *pdev) 108 { 109 struct device *dev = &pdev->dev; 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 = device_property_read_string(dev, "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 = device_property_read_u32(dev, "hw_margin_ms", &hw_margin); 140 if (ret) 141 return ret; 142 /* Disallow values lower than 2 and higher than 65535 ms */ 143 if (hw_margin < 2 || hw_margin > 65535) 144 return -EINVAL; 145 146 priv->always_running = device_property_read_bool(dev, "always-running"); 147 148 watchdog_set_drvdata(&priv->wdd, priv); 149 150 priv->wdd.info = &gpio_wdt_ident; 151 priv->wdd.ops = &gpio_wdt_ops; 152 priv->wdd.min_timeout = SOFT_TIMEOUT_MIN; 153 priv->wdd.max_hw_heartbeat_ms = hw_margin; 154 priv->wdd.parent = dev; 155 priv->wdd.timeout = SOFT_TIMEOUT_DEF; 156 157 watchdog_init_timeout(&priv->wdd, 0, dev); 158 watchdog_set_nowayout(&priv->wdd, nowayout); 159 160 watchdog_stop_on_reboot(&priv->wdd); 161 162 if (priv->always_running) 163 gpio_wdt_start(&priv->wdd); 164 165 return devm_watchdog_register_device(dev, &priv->wdd); 166 } 167 168 static const struct of_device_id gpio_wdt_dt_ids[] = { 169 { .compatible = "linux,wdt-gpio", }, 170 { } 171 }; 172 MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids); 173 174 static struct platform_driver gpio_wdt_driver = { 175 .driver = { 176 .name = "gpio-wdt", 177 .of_match_table = gpio_wdt_dt_ids, 178 }, 179 .probe = gpio_wdt_probe, 180 }; 181 182 #ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL 183 static int __init gpio_wdt_init(void) 184 { 185 return platform_driver_register(&gpio_wdt_driver); 186 } 187 arch_initcall(gpio_wdt_init); 188 #else 189 module_platform_driver(gpio_wdt_driver); 190 #endif 191 192 MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>"); 193 MODULE_DESCRIPTION("GPIO Watchdog"); 194 MODULE_LICENSE("GPL"); 195