1 /*
2  * Watchdog driver for Atmel AT91SAM9x processors.
3  *
4  * Copyright (C) 2008 Renaud CERRATO r.cerrato@til-technologies.fr
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 /*
13  * The Watchdog Timer Mode Register can be only written to once. If the
14  * timeout need to be set from Linux, be sure that the bootstrap or the
15  * bootloader doesn't write to this register.
16  */
17 
18 #include <linux/errno.h>
19 #include <linux/fs.h>
20 #include <linux/init.h>
21 #include <linux/io.h>
22 #include <linux/kernel.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/types.h>
28 #include <linux/watchdog.h>
29 #include <linux/jiffies.h>
30 #include <linux/timer.h>
31 #include <linux/bitops.h>
32 #include <linux/uaccess.h>
33 
34 #include <mach/at91_wdt.h>
35 
36 #define DRV_NAME "AT91SAM9 Watchdog"
37 
38 /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
39  * use this to convert a watchdog
40  * value from/to milliseconds.
41  */
42 #define ms_to_ticks(t)	(((t << 8) / 1000) - 1)
43 #define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
44 
45 /* Hardware timeout in seconds */
46 #define WDT_HW_TIMEOUT 2
47 
48 /* Timer heartbeat (500ms) */
49 #define WDT_TIMEOUT	(HZ/2)
50 
51 /* User land timeout */
52 #define WDT_HEARTBEAT 15
53 static int heartbeat = WDT_HEARTBEAT;
54 module_param(heartbeat, int, 0);
55 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
56 	"(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
57 
58 static int nowayout = WATCHDOG_NOWAYOUT;
59 module_param(nowayout, int, 0);
60 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
61 	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
62 
63 static void at91_ping(unsigned long data);
64 
65 static struct {
66 	unsigned long next_heartbeat;	/* the next_heartbeat for the timer */
67 	unsigned long open;
68 	char expect_close;
69 	struct timer_list timer;	/* The timer that pings the watchdog */
70 } at91wdt_private;
71 
72 /* ......................................................................... */
73 
74 
75 /*
76  * Reload the watchdog timer.  (ie, pat the watchdog)
77  */
78 static inline void at91_wdt_reset(void)
79 {
80 	at91_sys_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
81 }
82 
83 /*
84  * Timer tick
85  */
86 static void at91_ping(unsigned long data)
87 {
88 	if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
89 			(!nowayout && !at91wdt_private.open)) {
90 		at91_wdt_reset();
91 		mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
92 	} else
93 		printk(KERN_CRIT DRV_NAME": I will reset your machine !\n");
94 }
95 
96 /*
97  * Watchdog device is opened, and watchdog starts running.
98  */
99 static int at91_wdt_open(struct inode *inode, struct file *file)
100 {
101 	if (test_and_set_bit(0, &at91wdt_private.open))
102 		return -EBUSY;
103 
104 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
105 	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
106 
107 	return nonseekable_open(inode, file);
108 }
109 
110 /*
111  * Close the watchdog device.
112  */
113 static int at91_wdt_close(struct inode *inode, struct file *file)
114 {
115 	clear_bit(0, &at91wdt_private.open);
116 
117 	/* stop internal ping */
118 	if (!at91wdt_private.expect_close)
119 		del_timer(&at91wdt_private.timer);
120 
121 	at91wdt_private.expect_close = 0;
122 	return 0;
123 }
124 
125 /*
126  * Set the watchdog time interval in 1/256Hz (write-once)
127  * Counter is 12 bit.
128  */
129 static int at91_wdt_settimeout(unsigned int timeout)
130 {
131 	unsigned int reg;
132 	unsigned int mr;
133 
134 	/* Check if disabled */
135 	mr = at91_sys_read(AT91_WDT_MR);
136 	if (mr & AT91_WDT_WDDIS) {
137 		printk(KERN_ERR DRV_NAME": sorry, watchdog is disabled\n");
138 		return -EIO;
139 	}
140 
141 	/*
142 	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
143 	 *
144 	 * Since WDV is a 12-bit counter, the maximum period is
145 	 * 4096 / 256 = 16 seconds.
146 	 */
147 	reg = AT91_WDT_WDRSTEN	/* causes watchdog reset */
148 		/* | AT91_WDT_WDRPROC	causes processor reset only */
149 		| AT91_WDT_WDDBGHLT	/* disabled in debug mode */
150 		| AT91_WDT_WDD		/* restart at any time */
151 		| (timeout & AT91_WDT_WDV);  /* timer value */
152 	at91_sys_write(AT91_WDT_MR, reg);
153 
154 	return 0;
155 }
156 
157 static const struct watchdog_info at91_wdt_info = {
158 	.identity	= DRV_NAME,
159 	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
160 };
161 
162 /*
163  * Handle commands from user-space.
164  */
165 static long at91_wdt_ioctl(struct file *file,
166 		unsigned int cmd, unsigned long arg)
167 {
168 	void __user *argp = (void __user *)arg;
169 	int __user *p = argp;
170 	int new_value;
171 
172 	switch (cmd) {
173 	case WDIOC_GETSUPPORT:
174 		return copy_to_user(argp, &at91_wdt_info,
175 				    sizeof(at91_wdt_info)) ? -EFAULT : 0;
176 
177 	case WDIOC_GETSTATUS:
178 	case WDIOC_GETBOOTSTATUS:
179 		return put_user(0, p);
180 
181 	case WDIOC_KEEPALIVE:
182 		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
183 		return 0;
184 
185 	case WDIOC_SETTIMEOUT:
186 		if (get_user(new_value, p))
187 			return -EFAULT;
188 
189 		heartbeat = new_value;
190 		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
191 
192 		return put_user(new_value, p);  /* return current value */
193 
194 	case WDIOC_GETTIMEOUT:
195 		return put_user(heartbeat, p);
196 	}
197 	return -ENOTTY;
198 }
199 
200 /*
201  * Pat the watchdog whenever device is written to.
202  */
203 static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
204 								loff_t *ppos)
205 {
206 	if (!len)
207 		return 0;
208 
209 	/* Scan for magic character */
210 	if (!nowayout) {
211 		size_t i;
212 
213 		at91wdt_private.expect_close = 0;
214 
215 		for (i = 0; i < len; i++) {
216 			char c;
217 			if (get_user(c, data + i))
218 				return -EFAULT;
219 			if (c == 'V') {
220 				at91wdt_private.expect_close = 42;
221 				break;
222 			}
223 		}
224 	}
225 
226 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
227 
228 	return len;
229 }
230 
231 /* ......................................................................... */
232 
233 static const struct file_operations at91wdt_fops = {
234 	.owner			= THIS_MODULE,
235 	.llseek			= no_llseek,
236 	.unlocked_ioctl	= at91_wdt_ioctl,
237 	.open			= at91_wdt_open,
238 	.release		= at91_wdt_close,
239 	.write			= at91_wdt_write,
240 };
241 
242 static struct miscdevice at91wdt_miscdev = {
243 	.minor		= WATCHDOG_MINOR,
244 	.name		= "watchdog",
245 	.fops		= &at91wdt_fops,
246 };
247 
248 static int __init at91wdt_probe(struct platform_device *pdev)
249 {
250 	int res;
251 
252 	if (at91wdt_miscdev.parent)
253 		return -EBUSY;
254 	at91wdt_miscdev.parent = &pdev->dev;
255 
256 	/* Set watchdog */
257 	res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
258 	if (res)
259 		return res;
260 
261 	res = misc_register(&at91wdt_miscdev);
262 	if (res)
263 		return res;
264 
265 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
266 	setup_timer(&at91wdt_private.timer, at91_ping, 0);
267 	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
268 
269 	printk(KERN_INFO DRV_NAME " enabled (heartbeat=%d sec, nowayout=%d)\n",
270 		heartbeat, nowayout);
271 
272 	return 0;
273 }
274 
275 static int __exit at91wdt_remove(struct platform_device *pdev)
276 {
277 	int res;
278 
279 	res = misc_deregister(&at91wdt_miscdev);
280 	if (!res)
281 		at91wdt_miscdev.parent = NULL;
282 
283 	return res;
284 }
285 
286 #ifdef CONFIG_PM
287 
288 static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
289 {
290 	return 0;
291 }
292 
293 static int at91wdt_resume(struct platform_device *pdev)
294 {
295 	return 0;
296 }
297 
298 #else
299 #define at91wdt_suspend	NULL
300 #define at91wdt_resume	NULL
301 #endif
302 
303 static struct platform_driver at91wdt_driver = {
304 	.remove		= __exit_p(at91wdt_remove),
305 	.suspend	= at91wdt_suspend,
306 	.resume		= at91wdt_resume,
307 	.driver		= {
308 		.name	= "at91_wdt",
309 		.owner	= THIS_MODULE,
310 	},
311 };
312 
313 static int __init at91sam_wdt_init(void)
314 {
315 	return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
316 }
317 
318 static void __exit at91sam_wdt_exit(void)
319 {
320 	platform_driver_unregister(&at91wdt_driver);
321 }
322 
323 module_init(at91sam_wdt_init);
324 module_exit(at91sam_wdt_exit);
325 
326 MODULE_AUTHOR("Renaud CERRATO <r.cerrato@til-technologies.fr>");
327 MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
328 MODULE_LICENSE("GPL");
329 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
330