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"); 197