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 						WDIOF_MAGICCLOSE,
161 };
162 
163 /*
164  * Handle commands from user-space.
165  */
166 static long at91_wdt_ioctl(struct file *file,
167 		unsigned int cmd, unsigned long arg)
168 {
169 	void __user *argp = (void __user *)arg;
170 	int __user *p = argp;
171 	int new_value;
172 
173 	switch (cmd) {
174 	case WDIOC_GETSUPPORT:
175 		return copy_to_user(argp, &at91_wdt_info,
176 				    sizeof(at91_wdt_info)) ? -EFAULT : 0;
177 
178 	case WDIOC_GETSTATUS:
179 	case WDIOC_GETBOOTSTATUS:
180 		return put_user(0, p);
181 
182 	case WDIOC_KEEPALIVE:
183 		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
184 		return 0;
185 
186 	case WDIOC_SETTIMEOUT:
187 		if (get_user(new_value, p))
188 			return -EFAULT;
189 
190 		heartbeat = new_value;
191 		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
192 
193 		return put_user(new_value, p);  /* return current value */
194 
195 	case WDIOC_GETTIMEOUT:
196 		return put_user(heartbeat, p);
197 	}
198 	return -ENOTTY;
199 }
200 
201 /*
202  * Pat the watchdog whenever device is written to.
203  */
204 static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
205 								loff_t *ppos)
206 {
207 	if (!len)
208 		return 0;
209 
210 	/* Scan for magic character */
211 	if (!nowayout) {
212 		size_t i;
213 
214 		at91wdt_private.expect_close = 0;
215 
216 		for (i = 0; i < len; i++) {
217 			char c;
218 			if (get_user(c, data + i))
219 				return -EFAULT;
220 			if (c == 'V') {
221 				at91wdt_private.expect_close = 42;
222 				break;
223 			}
224 		}
225 	}
226 
227 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
228 
229 	return len;
230 }
231 
232 /* ......................................................................... */
233 
234 static const struct file_operations at91wdt_fops = {
235 	.owner			= THIS_MODULE,
236 	.llseek			= no_llseek,
237 	.unlocked_ioctl	= at91_wdt_ioctl,
238 	.open			= at91_wdt_open,
239 	.release		= at91_wdt_close,
240 	.write			= at91_wdt_write,
241 };
242 
243 static struct miscdevice at91wdt_miscdev = {
244 	.minor		= WATCHDOG_MINOR,
245 	.name		= "watchdog",
246 	.fops		= &at91wdt_fops,
247 };
248 
249 static int __init at91wdt_probe(struct platform_device *pdev)
250 {
251 	int res;
252 
253 	if (at91wdt_miscdev.parent)
254 		return -EBUSY;
255 	at91wdt_miscdev.parent = &pdev->dev;
256 
257 	/* Set watchdog */
258 	res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
259 	if (res)
260 		return res;
261 
262 	res = misc_register(&at91wdt_miscdev);
263 	if (res)
264 		return res;
265 
266 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
267 	setup_timer(&at91wdt_private.timer, at91_ping, 0);
268 	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
269 
270 	printk(KERN_INFO DRV_NAME " enabled (heartbeat=%d sec, nowayout=%d)\n",
271 		heartbeat, nowayout);
272 
273 	return 0;
274 }
275 
276 static int __exit at91wdt_remove(struct platform_device *pdev)
277 {
278 	int res;
279 
280 	res = misc_deregister(&at91wdt_miscdev);
281 	if (!res)
282 		at91wdt_miscdev.parent = NULL;
283 
284 	return res;
285 }
286 
287 #ifdef CONFIG_PM
288 
289 static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
290 {
291 	return 0;
292 }
293 
294 static int at91wdt_resume(struct platform_device *pdev)
295 {
296 	return 0;
297 }
298 
299 #else
300 #define at91wdt_suspend	NULL
301 #define at91wdt_resume	NULL
302 #endif
303 
304 static struct platform_driver at91wdt_driver = {
305 	.remove		= __exit_p(at91wdt_remove),
306 	.suspend	= at91wdt_suspend,
307 	.resume		= at91wdt_resume,
308 	.driver		= {
309 		.name	= "at91_wdt",
310 		.owner	= THIS_MODULE,
311 	},
312 };
313 
314 static int __init at91sam_wdt_init(void)
315 {
316 	return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
317 }
318 
319 static void __exit at91sam_wdt_exit(void)
320 {
321 	platform_driver_unregister(&at91wdt_driver);
322 }
323 
324 module_init(at91sam_wdt_init);
325 module_exit(at91sam_wdt_exit);
326 
327 MODULE_AUTHOR("Renaud CERRATO <r.cerrato@til-technologies.fr>");
328 MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
329 MODULE_LICENSE("GPL");
330 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
331