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	priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
155	if (!gpio_is_valid(priv->gpio))
156		return priv->gpio;
157
158	priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
159
160	ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
161	if (ret)
162		return ret;
163	if (!strcmp(algo, "toggle")) {
164		priv->hw_algo = HW_ALGO_TOGGLE;
165		f = GPIOF_IN;
166	} else if (!strcmp(algo, "level")) {
167		priv->hw_algo = HW_ALGO_LEVEL;
168		f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
169	} else {
170		return -EINVAL;
171	}
172
173	ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
174				    dev_name(&pdev->dev));
175	if (ret)
176		return ret;
177
178	ret = of_property_read_u32(pdev->dev.of_node,
179				   "hw_margin_ms", &hw_margin);
180	if (ret)
181		return ret;
182	/* Disallow values lower than 2 and higher than 65535 ms */
183	if (hw_margin < 2 || hw_margin > 65535)
184		return -EINVAL;
185
186	/* Use safe value (1/2 of real timeout) */
187	priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
188
189	priv->always_running = of_property_read_bool(pdev->dev.of_node,
190						     "always-running");
191
192	watchdog_set_drvdata(&priv->wdd, priv);
193
194	priv->wdd.info		= &gpio_wdt_ident;
195	priv->wdd.ops		= &gpio_wdt_ops;
196	priv->wdd.min_timeout	= SOFT_TIMEOUT_MIN;
197	priv->wdd.max_timeout	= SOFT_TIMEOUT_MAX;
198	priv->wdd.parent	= &pdev->dev;
199
200	if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
201		priv->wdd.timeout = SOFT_TIMEOUT_DEF;
202
203	setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
204
205	watchdog_stop_on_reboot(&priv->wdd);
206
207	ret = watchdog_register_device(&priv->wdd);
208	if (ret)
209		return ret;
210
211	if (priv->always_running)
212		gpio_wdt_start_impl(priv);
213
214	return 0;
215}
216
217static int gpio_wdt_remove(struct platform_device *pdev)
218{
219	struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
220
221	del_timer_sync(&priv->timer);
222	watchdog_unregister_device(&priv->wdd);
223
224	return 0;
225}
226
227static const struct of_device_id gpio_wdt_dt_ids[] = {
228	{ .compatible = "linux,wdt-gpio", },
229	{ }
230};
231MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
232
233static struct platform_driver gpio_wdt_driver = {
234	.driver	= {
235		.name		= "gpio-wdt",
236		.of_match_table	= gpio_wdt_dt_ids,
237	},
238	.probe	= gpio_wdt_probe,
239	.remove	= gpio_wdt_remove,
240};
241
242#ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
243static int __init gpio_wdt_init(void)
244{
245	return platform_driver_register(&gpio_wdt_driver);
246}
247arch_initcall(gpio_wdt_init);
248#else
249module_platform_driver(gpio_wdt_driver);
250#endif
251
252MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
253MODULE_DESCRIPTION("GPIO Watchdog");
254MODULE_LICENSE("GPL");