1/*
2 *	W83877F Computer Watchdog Timer driver for Linux 2.4.x
3 *
4 *      Based on acquirewdt.c by Alan Cox,
5 *           and sbc60xxwdt.c by Jakob Oestergaard <jakob@ostenfeld.dk>
6 *
7 *	This program is free software; you can redistribute it and/or
8 *	modify it under the terms of the GNU General Public License
9 *	as published by the Free Software Foundation; either version
10 *	2 of the License, or (at your option) any later version.
11 *
12 *	The authors do NOT admit liability nor provide warranty for
13 *	any of this software. This material is provided "AS-IS" in
14 *      the hope that it may be useful for others.
15 *
16 *	(c) Copyright 2001    Scott Jennings <linuxdrivers@oro.net>
17 *
18 *           4/19 - 2001      [Initial revision]
19 *           9/27 - 2001      Added spinlocking
20 *
21 *
22 *  Theory of operation:
23 *  A Watchdog Timer (WDT) is a hardware circuit that can
24 *  reset the computer system in case of a software fault.
25 *  You probably knew that already.
26 *
27 *  Usually a userspace daemon will notify the kernel WDT driver
28 *  via the /proc/watchdog special device file that userspace is
29 *  still alive, at regular intervals.  When such a notification
30 *  occurs, the driver will usually tell the hardware watchdog
31 *  that everything is in order, and that the watchdog should wait
32 *  for yet another little while to reset the system.
33 *  If userspace fails (RAM error, kernel bug, whatever), the
34 *  notifications cease to occur, and the hardware watchdog will
35 *  reset the system (causing a reboot) after the timeout occurs.
36 *
37 *  This WDT driver is different from most other Linux WDT
38 *  drivers in that the driver will ping the watchdog by itself,
39 *  because this particular WDT has a very short timeout (1.6
40 *  seconds) and it would be insane to count on any userspace
41 *  daemon always getting scheduled within that time frame.
42 */
43
44#include <linux/module.h>
45#include <linux/version.h>
46#include <linux/types.h>
47#include <linux/errno.h>
48#include <linux/kernel.h>
49#include <linux/timer.h>
50#include <linux/sched.h>
51#include <linux/miscdevice.h>
52#include <linux/watchdog.h>
53#include <linux/slab.h>
54#include <linux/ioport.h>
55#include <linux/fcntl.h>
56#include <linux/smp_lock.h>
57#include <asm/io.h>
58#include <asm/uaccess.h>
59#include <asm/system.h>
60#include <linux/notifier.h>
61#include <linux/reboot.h>
62#include <linux/init.h>
63
64#define OUR_NAME "w83877f_wdt"
65
66#define ENABLE_W83877F_PORT 0x3F0
67#define ENABLE_W83877F 0x87
68#define DISABLE_W83877F 0xAA
69#define WDT_PING 0x443
70#define WDT_REGISTER 0x14
71#define WDT_ENABLE 0x9C
72#define WDT_DISABLE 0x8C
73
74/*
75 * The W83877F seems to be fixed at 1.6s timeout (at least on the
76 * EMACS PC-104 board I'm using). If we reset the watchdog every
77 * ~250ms we should be safe.  */
78
79#define WDT_INTERVAL (HZ/4+1)
80
81/*
82 * We must not require too good response from the userspace daemon.
83 * Here we require the userspace daemon to send us a heartbeat
84 * char to /dev/watchdog every 30 seconds.
85 */
86
87#define WDT_HEARTBEAT (HZ * 30)
88
89static void wdt_timer_ping(unsigned long);
90static struct timer_list timer;
91static unsigned long next_heartbeat;
92static unsigned long wdt_is_open;
93static int wdt_expect_close;
94static spinlock_t wdt_spinlock;
95
96/*
97 *	Whack the dog
98 */
99
100static void wdt_timer_ping(unsigned long data)
101{
102	/* If we got a heartbeat pulse within the WDT_US_INTERVAL
103	 * we agree to ping the WDT
104	 */
105	if(time_before(jiffies, next_heartbeat))
106	{
107		/* Ping the WDT */
108		spin_lock(&wdt_spinlock);
109
110		/* Ping the WDT by reading from WDT_PING */
111		inb_p(WDT_PING);
112
113		/* Re-set the timer interval */
114		timer.expires = jiffies + WDT_INTERVAL;
115		add_timer(&timer);
116
117		spin_unlock(&wdt_spinlock);
118
119	} else {
120		printk(OUR_NAME ": Heartbeat lost! Will not ping the watchdog\n");
121	}
122}
123
124/*
125 * Utility routines
126 */
127
128static void wdt_change(int writeval)
129{
130	unsigned long flags;
131	spin_lock_irqsave(&wdt_spinlock, flags);
132
133	/* buy some time */
134	inb_p(WDT_PING);
135
136	/* make W83877F available */
137	outb_p(ENABLE_W83877F,  ENABLE_W83877F_PORT);
138	outb_p(ENABLE_W83877F,  ENABLE_W83877F_PORT);
139
140	/* enable watchdog */
141	outb_p(WDT_REGISTER,    ENABLE_W83877F_PORT);
142	outb_p(writeval,        ENABLE_W83877F_PORT+1);
143
144	/* lock the W8387FF away */
145	outb_p(DISABLE_W83877F, ENABLE_W83877F_PORT);
146
147	spin_unlock_irqrestore(&wdt_spinlock, flags);
148}
149
150static void wdt_startup(void)
151{
152	next_heartbeat = jiffies + WDT_HEARTBEAT;
153
154	/* Start the timer */
155	timer.expires = jiffies + WDT_INTERVAL;
156	add_timer(&timer);
157
158	wdt_change(WDT_ENABLE);
159
160	printk(OUR_NAME ": Watchdog timer is now enabled.\n");
161}
162
163static void wdt_turnoff(void)
164{
165	/* Stop the timer */
166	del_timer(&timer);
167
168	wdt_change(WDT_DISABLE);
169
170	printk(OUR_NAME ": Watchdog timer is now disabled...\n");
171}
172
173
174/*
175 * /dev/watchdog handling
176 */
177
178static ssize_t fop_write(struct file * file, const char * buf, size_t count, loff_t * ppos)
179{
180	/* We can't seek */
181	if(ppos != &file->f_pos)
182		return -ESPIPE;
183
184	/* See if we got the magic character */
185	if(count)
186	{
187		size_t ofs;
188
189		/* note: just in case someone wrote the magic character
190		 * five months ago... */
191		wdt_expect_close = 0;
192
193		/* now scan */
194		for(ofs = 0; ofs != count; ofs++)
195		{
196			char c;
197			if(get_user(c, buf + ofs))
198				return -EFAULT;
199			if(c == 'V')
200				wdt_expect_close = 1;
201		}
202
203		/* someone wrote to us, we should restart timer */
204		next_heartbeat = jiffies + WDT_HEARTBEAT;
205		return 1;
206	};
207	return 0;
208}
209
210static ssize_t fop_read(struct file * file, char * buf, size_t count, loff_t * ppos)
211{
212	/* No can do */
213	return -EINVAL;
214}
215
216static int fop_open(struct inode * inode, struct file * file)
217{
218	switch(MINOR(inode->i_rdev))
219	{
220		case WATCHDOG_MINOR:
221			/* Just in case we're already talking to someone... */
222			if(test_and_set_bit(0, &wdt_is_open)) {
223				spin_unlock(&wdt_spinlock);
224				return -EBUSY;
225			}
226			/* Good, fire up the show */
227			wdt_startup();
228			return 0;
229
230		default:
231			return -ENODEV;
232	}
233}
234
235static int fop_close(struct inode * inode, struct file * file)
236{
237	if(MINOR(inode->i_rdev) == WATCHDOG_MINOR)
238	{
239		if(wdt_expect_close)
240			wdt_turnoff();
241		else {
242			del_timer(&timer);
243			printk(OUR_NAME ": device file closed unexpectedly. Will not stop the WDT!\n");
244		}
245	}
246	clear_bit(0, &wdt_is_open);
247	return 0;
248}
249
250static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)
251{
252	static struct watchdog_info ident=
253	{
254		WDIOF_MAGICCLOSE,
255		1,
256		"W83877F"
257	};
258
259	switch(cmd)
260	{
261		default:
262			return -ENOIOCTLCMD;
263		case WDIOC_GETSUPPORT:
264			return copy_to_user((struct watchdog_info *)arg, &ident, sizeof(ident))?-EFAULT:0;
265		case WDIOC_KEEPALIVE:
266			next_heartbeat = jiffies + WDT_HEARTBEAT;
267			return 0;
268	}
269}
270
271static struct file_operations wdt_fops = {
272	owner:		THIS_MODULE,
273	llseek:		no_llseek,
274	read:		fop_read,
275	write:		fop_write,
276	open:		fop_open,
277	release:	fop_close,
278	ioctl:		fop_ioctl
279};
280
281static struct miscdevice wdt_miscdev = {
282	WATCHDOG_MINOR,
283	"watchdog",
284	&wdt_fops
285};
286
287/*
288 *	Notifier for system down
289 */
290
291static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
292	void *unused)
293{
294	if(code==SYS_DOWN || code==SYS_HALT)
295		wdt_turnoff();
296	return NOTIFY_DONE;
297}
298
299/*
300 *	The WDT needs to learn about soft shutdowns in order to
301 *	turn the timebomb registers off.
302 */
303
304static struct notifier_block wdt_notifier=
305{
306	wdt_notify_sys,
307	0,
308	0
309};
310
311static void __exit w83877f_wdt_unload(void)
312{
313	wdt_turnoff();
314
315	/* Deregister */
316	misc_deregister(&wdt_miscdev);
317
318	unregister_reboot_notifier(&wdt_notifier);
319	release_region(WDT_PING,1);
320	release_region(ENABLE_W83877F_PORT,2);
321}
322
323static int __init w83877f_wdt_init(void)
324{
325	int rc = -EBUSY;
326
327	spin_lock_init(&wdt_spinlock);
328
329	if (!request_region(ENABLE_W83877F_PORT, 2, "W83877F WDT"))
330		goto err_out;
331	if (!request_region(WDT_PING, 1, "W8387FF WDT"))
332		goto err_out_region1;
333
334	init_timer(&timer);
335	timer.function = wdt_timer_ping;
336	timer.data = 0;
337
338	rc = misc_register(&wdt_miscdev);
339	if (rc)
340		goto err_out_region2;
341
342	rc = register_reboot_notifier(&wdt_notifier);
343	if (rc)
344		goto err_out_miscdev;
345
346	printk(KERN_INFO OUR_NAME ": WDT driver for W83877F initialised.\n");
347
348	return 0;
349
350err_out_miscdev:
351	misc_deregister(&wdt_miscdev);
352err_out_region2:
353	release_region(WDT_PING,1);
354err_out_region1:
355	release_region(ENABLE_W83877F_PORT,2);
356err_out:
357	return rc;
358}
359
360module_init(w83877f_wdt_init);
361module_exit(w83877f_wdt_unload);
362
363MODULE_AUTHOR("Scott and Bill Jennings");
364MODULE_DESCRIPTION("Driver for watchdog timer in w83877f chip");
365MODULE_LICENSE("GPL");
366EXPORT_NO_SYMBOLS;
367