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_start_impl(struct gpio_wdt_priv *priv)
54{
55	priv->state = priv->active_low;
56	gpio_direction_output(priv->gpio, priv->state);
57	priv->last_jiffies = jiffies;
58	mod_timer(&priv->timer, priv->last_jiffies + priv->hw_margin);
59}
60
61static int gpio_wdt_start(struct watchdog_device *wdd)
62{
63	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
64
65	gpio_wdt_start_impl(priv);
66	priv->armed = true;
67
68	return 0;
69}
70
71static int gpio_wdt_stop(struct watchdog_device *wdd)
72{
73	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
74
75	priv->armed = false;
76	if (!priv->always_running) {
77		mod_timer(&priv->timer, 0);
78		gpio_wdt_disable(priv);
79	}
80
81	return 0;
82}
83
84static int gpio_wdt_ping(struct watchdog_device *wdd)
85{
86	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
87
88	priv->last_jiffies = jiffies;
89
90	return 0;
91}
92
93static int gpio_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
94{
95	wdd->timeout = t;
96
97	return gpio_wdt_ping(wdd);
98}
99
100static void gpio_wdt_hwping(unsigned long data)
101{
102	struct watchdog_device *wdd = (struct watchdog_device *)data;
103	struct gpio_wdt_priv *priv = watchdog_get_drvdata(wdd);
104
105	if (priv->armed && time_after(jiffies, priv->last_jiffies +
106				      msecs_to_jiffies(wdd->timeout * 1000))) {
107		dev_crit(wdd->dev, "Timer expired. System will reboot soon!\n");
108		return;
109	}
110
111	/* Restart timer */
112	mod_timer(&priv->timer, jiffies + priv->hw_margin);
113
114	switch (priv->hw_algo) {
115	case HW_ALGO_TOGGLE:
116		/* Toggle output pin */
117		priv->state = !priv->state;
118		gpio_set_value_cansleep(priv->gpio, priv->state);
119		break;
120	case HW_ALGO_LEVEL:
121		/* Pulse */
122		gpio_set_value_cansleep(priv->gpio, !priv->active_low);
123		udelay(1);
124		gpio_set_value_cansleep(priv->gpio, priv->active_low);
125		break;
126	}
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 (!strncmp(algo, "toggle", 6)) {
186		priv->hw_algo = HW_ALGO_TOGGLE;
187		f = GPIOF_IN;
188	} else if (!strncmp(algo, "level", 5)) {
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
221	if (watchdog_init_timeout(&priv->wdd, 0, &pdev->dev) < 0)
222		priv->wdd.timeout = SOFT_TIMEOUT_DEF;
223
224	setup_timer(&priv->timer, gpio_wdt_hwping, (unsigned long)&priv->wdd);
225
226	ret = watchdog_register_device(&priv->wdd);
227	if (ret)
228		return ret;
229
230	priv->notifier.notifier_call = gpio_wdt_notify_sys;
231	ret = register_reboot_notifier(&priv->notifier);
232	if (ret)
233		goto error_unregister;
234
235	if (priv->always_running)
236		gpio_wdt_start_impl(priv);
237
238	return 0;
239
240error_unregister:
241	watchdog_unregister_device(&priv->wdd);
242	return ret;
243}
244
245static int gpio_wdt_remove(struct platform_device *pdev)
246{
247	struct gpio_wdt_priv *priv = platform_get_drvdata(pdev);
248
249	del_timer_sync(&priv->timer);
250	unregister_reboot_notifier(&priv->notifier);
251	watchdog_unregister_device(&priv->wdd);
252
253	return 0;
254}
255
256static const struct of_device_id gpio_wdt_dt_ids[] = {
257	{ .compatible = "linux,wdt-gpio", },
258	{ }
259};
260MODULE_DEVICE_TABLE(of, gpio_wdt_dt_ids);
261
262static struct platform_driver gpio_wdt_driver = {
263	.driver	= {
264		.name		= "gpio-wdt",
265		.of_match_table	= gpio_wdt_dt_ids,
266	},
267	.probe	= gpio_wdt_probe,
268	.remove	= gpio_wdt_remove,
269};
270module_platform_driver(gpio_wdt_driver);
271
272MODULE_AUTHOR("Alexander Shiyan <shc_work@mail.ru>");
273MODULE_DESCRIPTION("GPIO Watchdog");
274MODULE_LICENSE("GPL");
275