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/notifier.h>
16#include <linux/of_gpio.h>
17#include <linux/platform_device.h>
18#include <linux/reboot.h>
19#include <linux/watchdog.h>
20
21#define SOFT_TIMEOUT_MIN	1
22#define SOFT_TIMEOUT_DEF	60
23#define SOFT_TIMEOUT_MAX	0xffff
24
25enum {
26	HW_ALGO_TOGGLE,
27	HW_ALGO_LEVEL,
28};
29
30struct gpio_wdt_priv {
31	int			gpio;
32	bool			active_low;
33	bool			state;
34	bool			always_running;
35	bool			armed;
36	unsigned int		hw_algo;
37	unsigned int		hw_margin;
38	unsigned long		last_jiffies;
39	struct notifier_block	notifier;
40	struct timer_list	timer;
41	struct watchdog_device	wdd;
42};
43
44static void gpio_wdt_disable(struct gpio_wdt_priv *priv)
45{
46	gpio_set_value_cansleep(priv->gpio, !priv->active_low);
47
48	/* Put GPIO back to tristate */
49	if (priv->hw_algo == HW_ALGO_TOGGLE)
50		gpio_direction_input(priv->gpio);
51}
52
53static void gpio_wdt_hwping(unsigned long data)
54{
55	struct watchdog_device *wdd = (struct watchdog_device *)data;
56	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
57
58	if (priv->armed && time_after(jiffies, priv->last_jiffies +
59				      msecs_to_jiffies(wdd->timeout * 1000))) {
60		dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
61		return;
62	}
63
64	/* Restart timer */
65	mod_timer(&priv->timer, jiffies + priv->hw_margin);
66
67	switch (priv->hw_algo) {
68	case HW_ALGO_TOGGLE:
69		/* Toggle output pin */
70		priv->state = !priv->state;
71		gpio_set_value_cansleep(priv->gpio, priv->state);
72		break;
73	case HW_ALGO_LEVEL:
74		/* Pulse */
75		gpio_set_value_cansleep(priv->gpio, !priv->active_low);
76		udelay(1);
77		gpio_set_value_cansleep(priv->gpio, priv->active_low);
78		break;
79	}
80}
81
82static void gpio_wdt_start_impl(struct gpio_wdt_priv *priv)
83{
84	priv->state = priv->active_low;
85	gpio_direction_output(priv->gpio, priv->state);
86	priv->last_jiffies = jiffies;
87	gpio_wdt_hwping((unsigned long)&priv->wdd);
88}
89
90static int gpio_wdt_start(struct watchdog_device *wdd)
91{
92	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
93
94	gpio_wdt_start_impl(priv);
95	priv->armed = true;
96
97	return 0;
98}
99
100static int gpio_wdt_stop(struct watchdog_device *wdd)
101{
102	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
103
104	priv->armed = false;
105	if (!priv->always_running) {
106		mod_timer(&priv->timer, 0);
107		gpio_wdt_disable(priv);
108	}
109
110	return 0;
111}
112
113static int gpio_wdt_ping(struct watchdog_device *wdd)
114{
115	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
116
117	priv->last_jiffies = jiffies;
118
119	return 0;
120}
121
122static int gpio_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
123{
124	wdd->timeout = t;
125
126	return gpio_wdt_ping(wdd);
127}
128
129static int gpio_wdt_notify_sys(struct notifier_block *nb, unsigned long code,
130			       void *unused)
131{
132	struct gpio_wdt_priv *priv = container_of(nb, struct gpio_wdt_priv,
133						  notifier);
134
135	mod_timer(&priv->timer, 0);
136
137	switch (code) {
138	case SYS_HALT:
139	case SYS_POWER_OFF:
140		gpio_wdt_disable(priv);
141		break;
142	default:
143		break;
144	}
145
146	return NOTIFY_DONE;
147}
148
149static const struct watchdog_info gpio_wdt_ident = {
150	.options	= WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING |
151			  WDIOF_SETTIMEOUT,
152	.identity	= "GPIO Watchdog",
153};
154
155static const struct watchdog_ops gpio_wdt_ops = {
156	.owner		= THIS_MODULE,
157	.start		= gpio_wdt_start,
158	.stop		= gpio_wdt_stop,
159	.ping		= gpio_wdt_ping,
160	.set_timeout	= gpio_wdt_set_timeout,
161};
162
163static int gpio_wdt_probe(struct platform_device *pdev)
164{
165	struct gpio_wdt_priv *priv;
166	enum of_gpio_flags flags;
167	unsigned int hw_margin;
168	unsigned long f = 0;
169	const char *algo;
170	int ret;
171
172	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
173	if (!priv)
174		return -ENOMEM;
175
176	priv->gpio = of_get_gpio_flags(pdev->dev.of_node, 0, &flags);
177	if (!gpio_is_valid(priv->gpio))
178		return priv->gpio;
179
180	priv->active_low = flags & OF_GPIO_ACTIVE_LOW;
181
182	ret = of_property_read_string(pdev->dev.of_node, "hw_algo", &algo);
183	if (ret)
184		return ret;
185	if (!strcmp(algo, "toggle")) {
186		priv->hw_algo = HW_ALGO_TOGGLE;
187		f = GPIOF_IN;
188	} else if (!strcmp(algo, "level")) {
189		priv->hw_algo = HW_ALGO_LEVEL;
190		f = priv->active_low ? GPIOF_OUT_INIT_HIGH : GPIOF_OUT_INIT_LOW;
191	} else {
192		return -EINVAL;
193	}
194
195	ret = devm_gpio_request_one(&pdev->dev, priv->gpio, f,
196				    dev_name(&pdev->dev));
197	if (ret)
198		return ret;
199
200	ret = of_property_read_u32(pdev->dev.of_node,
201				   "hw_margin_ms", &hw_margin);
202	if (ret)
203		return ret;
204	/* Disallow values lower than 2 and higher than 65535 ms */
205	if (hw_margin < 2 || hw_margin > 65535)
206		return -EINVAL;
207
208	/* Use safe value (1/2 of real timeout) */
209	priv->hw_margin = msecs_to_jiffies(hw_margin / 2);
210
211	priv->always_running = of_property_read_bool(pdev->dev.of_node,
212						     "always-running");
213
214	watchdog_set_drvdata(&priv->wdd, priv);
215
216	priv->wdd.info		= &gpio_wdt_ident;
217	priv->wdd.ops		= &gpio_wdt_ops;
218	priv->wdd.min_timeout	= SOFT_TIMEOUT_MIN;
219	priv->wdd.max_timeout	= SOFT_TIMEOUT_MAX;
220	priv->wdd.parent	= &pdev->dev;
221
222	if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
223		priv->wdd.timeout = SOFT_TIMEOUT_DEF;
224
225	setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
226
227	ret = watchdog_register_device(&priv->wdd);
228	if (ret)
229		return ret;
230
231	priv->notifier.notifier_call = gpio_wdt_notify_sys;
232	ret = register_reboot_notifier(&priv->notifier);
233	if (ret)
234		goto error_unregister;
235
236	if (priv->always_running)
237		gpio_wdt_start_impl(priv);
238
239	return 0;
240
241error_unregister:
242	watchdog_unregister_device(&priv->wdd);
243	return ret;
244}
245
246static int gpio_wdt_remove(struct platform_device *pdev)
247{
248	struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
249
250	del_timer_sync(&priv->timer);
251	unregister_reboot_notifier(&priv->notifier);
252	watchdog_unregister_device(&priv->wdd);
253
254	return 0;
255}
256
257static const struct of_device_id gpio_wdt_dt_ids[] = {
258	{ .compatible = "linux,wdt-gpio", },
259	{ }
260};
261MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
262
263static struct platform_driver gpio_wdt_driver = {
264	.driver	= {
265		.name		= "gpio-wdt",
266		.of_match_table	= gpio_wdt_dt_ids,
267	},
268	.probe	= gpio_wdt_probe,
269	.remove	= gpio_wdt_remove,
270};
271
272#ifdef CONFIG_GPIO_WATCHDOG_ARCH_INITCALL
273static int __init gpio_wdt_init(void)
274{
275	return platform_driver_register(&gpio_wdt_driver);
276}
277arch_initcall(gpio_wdt_init);
278#else
279module_platform_driver(gpio_wdt_driver);
280#endif
281
282MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
283MODULE_DESCRIPTION("GPIO Watchdog");
284MODULE_LICENSE("GPL");
285