1 /*
2  * Watchdog driver for Atmel AT91RM9200 (Thunder)
3  *
4  *  Copyright (C) 2003 SAN People (Pty) Ltd
5  *
6  * This program is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License
8  * as published by the Free Software Foundation; either version
9  * 2 of the License, or (at your option) any later version.
10  */
11 
12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
13 
14 #include <linux/bitops.h>
15 #include <linux/delay.h>
16 #include <linux/errno.h>
17 #include <linux/fs.h>
18 #include <linux/init.h>
19 #include <linux/io.h>
20 #include <linux/kernel.h>
21 #include <linux/mfd/syscon.h>
22 #include <linux/mfd/syscon/atmel-st.h>
23 #include <linux/miscdevice.h>
24 #include <linux/module.h>
25 #include <linux/moduleparam.h>
26 #include <linux/platform_device.h>
27 #include <linux/reboot.h>
28 #include <linux/regmap.h>
29 #include <linux/types.h>
30 #include <linux/watchdog.h>
31 #include <linux/uaccess.h>
32 #include <linux/of.h>
33 #include <linux/of_device.h>
34 
35 #define WDT_DEFAULT_TIME	5	/* seconds */
36 #define WDT_MAX_TIME		256	/* seconds */
37 
38 static int wdt_time = WDT_DEFAULT_TIME;
39 static bool nowayout = WATCHDOG_NOWAYOUT;
40 static struct regmap *regmap_st;
41 
42 module_param(wdt_time, int, 0);
43 MODULE_PARM_DESC(wdt_time, "Watchdog time in seconds. (default="
44 				__MODULE_STRING(WDT_DEFAULT_TIME) ")");
45 
46 #ifdef CONFIG_WATCHDOG_NOWAYOUT
47 module_param(nowayout, bool, 0);
48 MODULE_PARM_DESC(nowayout,
49 		"Watchdog cannot be stopped once started (default="
50 				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
51 #endif
52 
53 
54 static unsigned long at91wdt_busy;
55 
56 /* ......................................................................... */
57 
58 static int at91rm9200_restart(struct notifier_block *this,
59 					unsigned long mode, void *cmd)
60 {
61 	/*
62 	 * Perform a hardware reset with the use of the Watchdog timer.
63 	 */
64 	regmap_write(regmap_st, AT91_ST_WDMR,
65 		     AT91_ST_RSTEN | AT91_ST_EXTEN | 1);
66 	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
67 
68 	mdelay(2000);
69 
70 	pr_emerg("Unable to restart system\n");
71 	return NOTIFY_DONE;
72 }
73 
74 static struct notifier_block at91rm9200_restart_nb = {
75 	.notifier_call = at91rm9200_restart,
76 	.priority = 192,
77 };
78 
79 /*
80  * Disable the watchdog.
81  */
82 static inline void at91_wdt_stop(void)
83 {
84 	regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN);
85 }
86 
87 /*
88  * Enable and reset the watchdog.
89  */
90 static inline void at91_wdt_start(void)
91 {
92 	regmap_write(regmap_st, AT91_ST_WDMR, AT91_ST_EXTEN | AT91_ST_RSTEN |
93 				(((65536 * wdt_time) >> 8) & AT91_ST_WDV));
94 	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
95 }
96 
97 /*
98  * Reload the watchdog timer.  (ie, pat the watchdog)
99  */
100 static inline void at91_wdt_reload(void)
101 {
102 	regmap_write(regmap_st, AT91_ST_CR, AT91_ST_WDRST);
103 }
104 
105 /* ......................................................................... */
106 
107 /*
108  * Watchdog device is opened, and watchdog starts running.
109  */
110 static int at91_wdt_open(struct inode *inode, struct file *file)
111 {
112 	if (test_and_set_bit(0, &at91wdt_busy))
113 		return -EBUSY;
114 
115 	at91_wdt_start();
116 	return nonseekable_open(inode, file);
117 }
118 
119 /*
120  * Close the watchdog device.
121  * If CONFIG_WATCHDOG_NOWAYOUT is NOT defined then the watchdog is also
122  *  disabled.
123  */
124 static int at91_wdt_close(struct inode *inode, struct file *file)
125 {
126 	/* Disable the watchdog when file is closed */
127 	if (!nowayout)
128 		at91_wdt_stop();
129 
130 	clear_bit(0, &at91wdt_busy);
131 	return 0;
132 }
133 
134 /*
135  * Change the watchdog time interval.
136  */
137 static int at91_wdt_settimeout(int new_time)
138 {
139 	/*
140 	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
141 	 *
142 	 * Since WDV is a 16-bit counter, the maximum period is
143 	 * 65536 / 256 = 256 seconds.
144 	 */
145 	if ((new_time <= 0) || (new_time > WDT_MAX_TIME))
146 		return -EINVAL;
147 
148 	/* Set new watchdog time. It will be used when
149 	   at91_wdt_start() is called. */
150 	wdt_time = new_time;
151 	return 0;
152 }
153 
154 static const struct watchdog_info at91_wdt_info = {
155 	.identity	= "at91 watchdog",
156 	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
157 };
158 
159 /*
160  * Handle commands from user-space.
161  */
162 static long at91_wdt_ioctl(struct file *file,
163 					unsigned int cmd, unsigned long arg)
164 {
165 	void __user *argp = (void __user *)arg;
166 	int __user *p = argp;
167 	int new_value;
168 
169 	switch (cmd) {
170 	case WDIOC_GETSUPPORT:
171 		return copy_to_user(argp, &at91_wdt_info,
172 				sizeof(at91_wdt_info)) ? -EFAULT : 0;
173 	case WDIOC_GETSTATUS:
174 	case WDIOC_GETBOOTSTATUS:
175 		return put_user(0, p);
176 	case WDIOC_SETOPTIONS:
177 		if (get_user(new_value, p))
178 			return -EFAULT;
179 		if (new_value & WDIOS_DISABLECARD)
180 			at91_wdt_stop();
181 		if (new_value & WDIOS_ENABLECARD)
182 			at91_wdt_start();
183 		return 0;
184 	case WDIOC_KEEPALIVE:
185 		at91_wdt_reload();	/* pat the watchdog */
186 		return 0;
187 	case WDIOC_SETTIMEOUT:
188 		if (get_user(new_value, p))
189 			return -EFAULT;
190 		if (at91_wdt_settimeout(new_value))
191 			return -EINVAL;
192 		/* Enable new time value */
193 		at91_wdt_start();
194 		/* Return current value */
195 		return put_user(wdt_time, p);
196 	case WDIOC_GETTIMEOUT:
197 		return put_user(wdt_time, p);
198 	default:
199 		return -ENOTTY;
200 	}
201 }
202 
203 /*
204  * Pat the watchdog whenever device is written to.
205  */
206 static ssize_t at91_wdt_write(struct file *file, const char *data,
207 						size_t len, loff_t *ppos)
208 {
209 	at91_wdt_reload();		/* pat the watchdog */
210 	return len;
211 }
212 
213 /* ......................................................................... */
214 
215 static const struct file_operations at91wdt_fops = {
216 	.owner		= THIS_MODULE,
217 	.llseek		= no_llseek,
218 	.unlocked_ioctl	= at91_wdt_ioctl,
219 	.open		= at91_wdt_open,
220 	.release	= at91_wdt_close,
221 	.write		= at91_wdt_write,
222 };
223 
224 static struct miscdevice at91wdt_miscdev = {
225 	.minor		= WATCHDOG_MINOR,
226 	.name		= "watchdog",
227 	.fops		= &at91wdt_fops,
228 };
229 
230 static int at91wdt_probe(struct platform_device *pdev)
231 {
232 	struct device *dev = &pdev->dev;
233 	struct device *parent;
234 	int res;
235 
236 	if (at91wdt_miscdev.parent)
237 		return -EBUSY;
238 	at91wdt_miscdev.parent = &pdev->dev;
239 
240 	parent = dev->parent;
241 	if (!parent) {
242 		dev_err(dev, "no parent\n");
243 		return -ENODEV;
244 	}
245 
246 	regmap_st = syscon_node_to_regmap(parent->of_node);
247 	if (!regmap_st)
248 		return -ENODEV;
249 
250 	res = misc_register(&at91wdt_miscdev);
251 	if (res)
252 		return res;
253 
254 	res = register_restart_handler(&at91rm9200_restart_nb);
255 	if (res)
256 		dev_warn(dev, "failed to register restart handler\n");
257 
258 	pr_info("AT91 Watchdog Timer enabled (%d seconds%s)\n",
259 		wdt_time, nowayout ? ", nowayout" : "");
260 	return 0;
261 }
262 
263 static int at91wdt_remove(struct platform_device *pdev)
264 {
265 	struct device *dev = &pdev->dev;
266 	int res;
267 
268 	res = unregister_restart_handler(&at91rm9200_restart_nb);
269 	if (res)
270 		dev_warn(dev, "failed to unregister restart handler\n");
271 
272 	res = misc_deregister(&at91wdt_miscdev);
273 	if (!res)
274 		at91wdt_miscdev.parent = NULL;
275 
276 	return res;
277 }
278 
279 static void at91wdt_shutdown(struct platform_device *pdev)
280 {
281 	at91_wdt_stop();
282 }
283 
284 #ifdef CONFIG_PM
285 
286 static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
287 {
288 	at91_wdt_stop();
289 	return 0;
290 }
291 
292 static int at91wdt_resume(struct platform_device *pdev)
293 {
294 	if (at91wdt_busy)
295 		at91_wdt_start();
296 	return 0;
297 }
298 
299 #else
300 #define at91wdt_suspend NULL
301 #define at91wdt_resume	NULL
302 #endif
303 
304 static const struct of_device_id at91_wdt_dt_ids[] = {
305 	{ .compatible = "atmel,at91rm9200-wdt" },
306 	{ /* sentinel */ }
307 };
308 MODULE_DEVICE_TABLE(of, at91_wdt_dt_ids);
309 
310 static struct platform_driver at91wdt_driver = {
311 	.probe		= at91wdt_probe,
312 	.remove		= at91wdt_remove,
313 	.shutdown	= at91wdt_shutdown,
314 	.suspend	= at91wdt_suspend,
315 	.resume		= at91wdt_resume,
316 	.driver		= {
317 		.name	= "atmel_st_watchdog",
318 		.of_match_table = at91_wdt_dt_ids,
319 	},
320 };
321 
322 static int __init at91_wdt_init(void)
323 {
324 	/* Check that the heartbeat value is within range;
325 	   if not reset to the default */
326 	if (at91_wdt_settimeout(wdt_time)) {
327 		at91_wdt_settimeout(WDT_DEFAULT_TIME);
328 		pr_info("wdt_time value must be 1 <= wdt_time <= 256, using %d\n",
329 			wdt_time);
330 	}
331 
332 	return platform_driver_register(&at91wdt_driver);
333 }
334 
335 static void __exit at91_wdt_exit(void)
336 {
337 	platform_driver_unregister(&at91wdt_driver);
338 }
339 
340 module_init(at91_wdt_init);
341 module_exit(at91_wdt_exit);
342 
343 MODULE_AUTHOR("Andrew Victor");
344 MODULE_DESCRIPTION("Watchdog driver for Atmel AT91RM9200");
345 MODULE_LICENSE("GPL");
346 MODULE_ALIAS("platform:atmel_st_watchdog");
347