1/*
  2 * Driver for watchdog device controlled through GPIO-line
  3 *
  4 * Author: 2013, Alexander Shiyan <shc_work@mail.ru>
  5 *
  6 * This program is free software; you can redistribute it and/or modify
  7 * it under the terms of the GNU General Public License as published by
  8 * the Free Software Foundation; either version 2 of the License, or
  9 * (at your option) any later version.
 10 */
 11
 12#include <linux/err.h>
 13#include <linux/delay.h>
 14#include <linux/module.h>
 15#include <linux/of_gpio.h>
 16#include <linux/platform_device.h>
 17#include <linux/watchdog.h>
 18
 19#define SOFT_TIMEOUT_MIN	1
 20#define SOFT_TIMEOUT_DEF	60
 21#define SOFT_TIMEOUT_MAX	0xffff
 22
 23enum {
 24	HW_ALGO_TOGGLE,
 25	HW_ALGO_LEVEL,
 26};
 27
 28struct gpio_wdt_priv {
 29	int			gpio;
 30	bool			active_low;
 31	bool			state;
 32	bool			always_running;
 33	bool			armed;
 34	unsigned int		hw_algo;
 35	unsigned int		hw_margin;
 36	unsigned long		last_jiffies;
 37	struct timer_list	timer;
 38	struct watchdog_device	wdd;
 39};
 40
 41static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
 42{
 43	gpio_set_value_cansleep(priv->gpio, !priv->active_low);
 44
 45	/* Put GPIO back to tristate */
 46	if (priv->hw_algo == HW_ALGO_TOGGLE)
 47		gpio_direction_input(priv->gpio);
 48}
 49
 50static void gpio_wdt_hwping(unsigned long data)
 51{
 52	struct watchdog_device *wdd = (struct watchdog_device *)data;
 53	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
 54
 55	if (priv->armed && time_after(jiffies, priv->last_jiffies +
 56				      msecs_to_jiffies(wdd->timeout * 1000))) {
 57		dev_crit(wdd->parent,
 58			 "Timer expired. System will reboot soon!\n");
 59		return;
 60	}
 61
 62	/* Restart timer */
 63	mod_timer(&priv->timer, jiffies + priv->hw_margin);
 64
 65	switch (priv->hw_algo) {
 66	case HW_ALGO_TOGGLE:
 67		/* Toggle output pin */
 68		priv->state = !priv->state;
 69		gpio_set_value_cansleep(priv->gpio, priv->state);
 70		break;
 71	case HW_ALGO_LEVEL:
 72		/* Pulse */
 73		gpio_set_value_cansleep(priv->gpio, !priv->active_low);
 74		udelay(1);
 75		gpio_set_value_cansleep(priv->gpio, priv->active_low);
 76		break;
 77	}
 78}
 79
 80static void gpio_wdt_start_impl(struct gpio_wdt_priv *priv)
 81{
 82	priv->state = priv->active_low;
 83	gpio_direction_output(priv->gpio, priv->state);
 84	priv->last_jiffies = jiffies;
 85	gpio_wdt_hwping((unsigned long)&priv->wdd);
 86}
 87
 88static int gpio_wdt_start(struct watchdog_device *wdd)
 89{
 90	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
 91
 92	gpio_wdt_start_impl(priv);
 93	priv->armed = true;
 94
 95	return 0;
 96}
 97
 98static int gpio_wdt_stop(struct watchdog_device *wdd)
 99{
100	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
101
102	priv->armed = false;
103	if (!priv->always_running) {
104		mod_timer(&priv->timer, 0);
105		gpio_wdt_disable(priv);
106	}
107
108	return 0;
109}
110
111static int gpio_wdt_ping(struct watchdog_device *wdd)
112{
113	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
114
115	priv->last_jiffies = jiffies;
116
117	return 0;
118}
119
120static int gpio_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
121{
122	wdd->timeout = t;
123
124	return gpio_wdt_ping(wdd);
125}
126
127static const struct watchdog_info gpio_wdt_ident = {
128	.options	= WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
129			  WDIOF_SETTIMEOUT,
130	.identity	= "GPIO Watchdog",
131};
132
133static const struct watchdog_ops gpio_wdt_ops = {
134	.owner		= THIS_MODULE,
135	.start		= gpio_wdt_start,
136	.stop		= gpio_wdt_stop,
137	.ping		= gpio_wdt_ping,
138	.set_timeout	= gpio_wdt_set_timeout,
139};
140
141static int gpio_wdt_probe(struct platform_device *pdev)
142{
143	struct gpio_wdt_priv *priv;
144	enum of_gpio_flags flags;
145	unsigned int hw_margin;
146	unsigned long f = 0;
147	const char *algo;
148	int ret;
149
150	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
151	if (!priv)
152		return -ENOMEM;
153
154	platform_set_drvdata(pdev, priv);
155
156	priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
157	if (!gpio_is_valid(priv->gpio))
158		return priv->gpio;
159
160	priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
161
162	ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
163	if (ret)
164		return ret;
165	if (!strcmp(algo, "toggle")) {
166		priv->hw_algo = HW_ALGO_TOGGLE;
167		f = GPIOF_IN;
168	} else if (!strcmp(algo, "level")) {
169		priv->hw_algo = HW_ALGO_LEVEL;
170		f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
171	} else {
172		return -EINVAL;
173	}
174
175	ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
176				    dev_name(&pdev->dev));
177	if (ret)
178		return ret;
179
180	ret = of_property_read_u32(pdev->dev.of_node,
181				   "hw_margin_ms", &hw_margin);
182	if (ret)
183		return ret;
184	/* Disallow values lower than 2 and higher than 65535 ms */
185	if (hw_margin < 2 || hw_margin > 65535)
186		return -EINVAL;
187
188	/* Use safe value (1/2 of real timeout) */
189	priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
190
191	priv->always_running = of_property_read_bool(pdev->dev.of_node,
192						     "always-running");
193
194	watchdog_set_drvdata(&priv->wdd, priv);
195
196	priv->wdd.info		= &gpio_wdt_ident;
197	priv->wdd.ops		= &gpio_wdt_ops;
198	priv->wdd.min_timeout	= SOFT_TIMEOUT_MIN;
199	priv->wdd.max_timeout	= SOFT_TIMEOUT_MAX;
200	priv->wdd.parent	= &pdev->dev;
201
202	if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
203		priv->wdd.timeout = SOFT_TIMEOUT_DEF;
204
205	setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
206
207	watchdog_stop_on_reboot(&priv->wdd);
208
209	ret = watchdog_register_device(&priv->wdd);
210	if (ret)
211		return ret;
212
213	if (priv->always_running)
214		gpio_wdt_start_impl(priv);
215
216	return 0;
217}
218
219static int gpio_wdt_remove(struct platform_device *pdev)
220{
221	struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
222
223	del_timer_sync(&priv->timer);
224	watchdog_unregister_device(&priv->wdd);
225
226	return 0;
227}
228
229static const struct of_device_id gpio_wdt_dt_ids[] = {
230	{ .compatible = "linux,wdt-gpio", },
231	{ }
232};
233MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
234
235static struct platform_driver gpio_wdt_driver = {
236	.driver	= {
237		.name		= "gpio-wdt",
238		.of_match_table	= gpio_wdt_dt_ids,
239	},
240	.probe	= gpio_wdt_probe,
241	.remove	= gpio_wdt_remove,
242};
243
244#ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
245static int __init gpio_wdt_init(void)
246{
247	return platform_driver_register(&gpio_wdt_driver);
248}
249arch_initcall(gpio_wdt_init);
250#else
251module_platform_driver(gpio_wdt_driver);
252#endif
253
254MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
255MODULE_DESCRIPTION("GPIO Watchdog");
256MODULE_LICENSE("GPL");