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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
19 
20 #include <linux/errno.h>
21 #include <linux/fs.h>
22 #include <linux/init.h>
23 #include <linux/io.h>
24 #include <linux/kernel.h>
25 #include <linux/miscdevice.h>
26 #include <linux/module.h>
27 #include <linux/moduleparam.h>
28 #include <linux/platform_device.h>
29 #include <linux/types.h>
30 #include <linux/watchdog.h>
31 #include <linux/jiffies.h>
32 #include <linux/timer.h>
33 #include <linux/bitops.h>
34 #include <linux/uaccess.h>
35 
36 #include "at91sam9_wdt.h"
37 
38 #define DRV_NAME "AT91SAM9 Watchdog"
39 
40 #define wdt_read(field) \
41 	__raw_readl(at91wdt_private.base + field)
42 #define wdt_write(field, val) \
43 	__raw_writel((val), at91wdt_private.base + field)
44 
45 /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
46  * use this to convert a watchdog
47  * value from/to milliseconds.
48  */
49 #define ms_to_ticks(t)	(((t << 8) / 1000) - 1)
50 #define ticks_to_ms(t)	(((t + 1) * 1000) >> 8)
51 
52 /* Hardware timeout in seconds */
53 #define WDT_HW_TIMEOUT 2
54 
55 /* Timer heartbeat (500ms) */
56 #define WDT_TIMEOUT	(HZ/2)
57 
58 /* User land timeout */
59 #define WDT_HEARTBEAT 15
60 static int heartbeat = WDT_HEARTBEAT;
61 module_param(heartbeat, int, 0);
62 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
63 	"(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
64 
65 static bool nowayout = WATCHDOG_NOWAYOUT;
66 module_param(nowayout, bool, 0);
67 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
68 	"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
69 
70 static void at91_ping(unsigned long data);
71 
72 static struct {
73 	void __iomem *base;
74 	unsigned long next_heartbeat;	/* the next_heartbeat for the timer */
75 	unsigned long open;
76 	char expect_close;
77 	struct timer_list timer;	/* The timer that pings the watchdog */
78 } at91wdt_private;
79 
80 /* ......................................................................... */
81 
82 
83 /*
84  * Reload the watchdog timer.  (ie, pat the watchdog)
85  */
86 static inline void at91_wdt_reset(void)
87 {
88 	wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
89 }
90 
91 /*
92  * Timer tick
93  */
94 static void at91_ping(unsigned long data)
95 {
96 	if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
97 			(!nowayout && !at91wdt_private.open)) {
98 		at91_wdt_reset();
99 		mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
100 	} else
101 		pr_crit("I will reset your machine !\n");
102 }
103 
104 /*
105  * Watchdog device is opened, and watchdog starts running.
106  */
107 static int at91_wdt_open(struct inode *inode, struct file *file)
108 {
109 	if (test_and_set_bit(0, &at91wdt_private.open))
110 		return -EBUSY;
111 
112 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
113 	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
114 
115 	return nonseekable_open(inode, file);
116 }
117 
118 /*
119  * Close the watchdog device.
120  */
121 static int at91_wdt_close(struct inode *inode, struct file *file)
122 {
123 	clear_bit(0, &at91wdt_private.open);
124 
125 	/* stop internal ping */
126 	if (!at91wdt_private.expect_close)
127 		del_timer(&at91wdt_private.timer);
128 
129 	at91wdt_private.expect_close = 0;
130 	return 0;
131 }
132 
133 /*
134  * Set the watchdog time interval in 1/256Hz (write-once)
135  * Counter is 12 bit.
136  */
137 static int at91_wdt_settimeout(unsigned int timeout)
138 {
139 	unsigned int reg;
140 	unsigned int mr;
141 
142 	/* Check if disabled */
143 	mr = wdt_read(AT91_WDT_MR);
144 	if (mr & AT91_WDT_WDDIS) {
145 		pr_err("sorry, watchdog is disabled\n");
146 		return -EIO;
147 	}
148 
149 	/*
150 	 * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
151 	 *
152 	 * Since WDV is a 12-bit counter, the maximum period is
153 	 * 4096 / 256 = 16 seconds.
154 	 */
155 	reg = AT91_WDT_WDRSTEN	/* causes watchdog reset */
156 		/* | AT91_WDT_WDRPROC	causes processor reset only */
157 		| AT91_WDT_WDDBGHLT	/* disabled in debug mode */
158 		| AT91_WDT_WDD		/* restart at any time */
159 		| (timeout & AT91_WDT_WDV);  /* timer value */
160 	wdt_write(AT91_WDT_MR, reg);
161 
162 	return 0;
163 }
164 
165 static const struct watchdog_info at91_wdt_info = {
166 	.identity	= DRV_NAME,
167 	.options	= WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
168 						WDIOF_MAGICCLOSE,
169 };
170 
171 /*
172  * Handle commands from user-space.
173  */
174 static long at91_wdt_ioctl(struct file *file,
175 		unsigned int cmd, unsigned long arg)
176 {
177 	void __user *argp = (void __user *)arg;
178 	int __user *p = argp;
179 	int new_value;
180 
181 	switch (cmd) {
182 	case WDIOC_GETSUPPORT:
183 		return copy_to_user(argp, &at91_wdt_info,
184 				    sizeof(at91_wdt_info)) ? -EFAULT : 0;
185 
186 	case WDIOC_GETSTATUS:
187 	case WDIOC_GETBOOTSTATUS:
188 		return put_user(0, p);
189 
190 	case WDIOC_KEEPALIVE:
191 		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
192 		return 0;
193 
194 	case WDIOC_SETTIMEOUT:
195 		if (get_user(new_value, p))
196 			return -EFAULT;
197 
198 		heartbeat = new_value;
199 		at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
200 
201 		return put_user(new_value, p);  /* return current value */
202 
203 	case WDIOC_GETTIMEOUT:
204 		return put_user(heartbeat, p);
205 	}
206 	return -ENOTTY;
207 }
208 
209 /*
210  * Pat the watchdog whenever device is written to.
211  */
212 static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
213 								loff_t *ppos)
214 {
215 	if (!len)
216 		return 0;
217 
218 	/* Scan for magic character */
219 	if (!nowayout) {
220 		size_t i;
221 
222 		at91wdt_private.expect_close = 0;
223 
224 		for (i = 0; i < len; i++) {
225 			char c;
226 			if (get_user(c, data + i))
227 				return -EFAULT;
228 			if (c == 'V') {
229 				at91wdt_private.expect_close = 42;
230 				break;
231 			}
232 		}
233 	}
234 
235 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
236 
237 	return len;
238 }
239 
240 /* ......................................................................... */
241 
242 static const struct file_operations at91wdt_fops = {
243 	.owner			= THIS_MODULE,
244 	.llseek			= no_llseek,
245 	.unlocked_ioctl	= at91_wdt_ioctl,
246 	.open			= at91_wdt_open,
247 	.release		= at91_wdt_close,
248 	.write			= at91_wdt_write,
249 };
250 
251 static struct miscdevice at91wdt_miscdev = {
252 	.minor		= WATCHDOG_MINOR,
253 	.name		= "watchdog",
254 	.fops		= &at91wdt_fops,
255 };
256 
257 static int __init at91wdt_probe(struct platform_device *pdev)
258 {
259 	struct resource	*r;
260 	int res;
261 
262 	if (at91wdt_miscdev.parent)
263 		return -EBUSY;
264 	at91wdt_miscdev.parent = &pdev->dev;
265 
266 	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
267 	if (!r)
268 		return -ENODEV;
269 	at91wdt_private.base = ioremap(r->start, resource_size(r));
270 	if (!at91wdt_private.base) {
271 		dev_err(&pdev->dev, "failed to map registers, aborting.\n");
272 		return -ENOMEM;
273 	}
274 
275 	/* Set watchdog */
276 	res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
277 	if (res)
278 		return res;
279 
280 	res = misc_register(&at91wdt_miscdev);
281 	if (res)
282 		return res;
283 
284 	at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
285 	setup_timer(&at91wdt_private.timer, at91_ping, 0);
286 	mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
287 
288 	pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
289 		heartbeat, nowayout);
290 
291 	return 0;
292 }
293 
294 static int __exit at91wdt_remove(struct platform_device *pdev)
295 {
296 	int res;
297 
298 	res = misc_deregister(&at91wdt_miscdev);
299 	if (!res)
300 		at91wdt_miscdev.parent = NULL;
301 
302 	return res;
303 }
304 
305 static struct platform_driver at91wdt_driver = {
306 	.remove		= __exit_p(at91wdt_remove),
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