1/*
2 *	AMD Elan SC520 processor Watchdog Timer driver
3 *
4 *	Based on acquirewdt.c by Alan Cox,
5 *	     and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
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 *           9/27 - 2001      [Initial release]
18 *
19 *	Additional fixes Alan Cox
20 *	-	Fixed formatting
21 *	-	Removed debug printks
22 *	-	Fixed SMP built kernel deadlock
23 *	-	Switched to private locks not lock_kernel
24 *	-	Used ioremap/writew/readw
25 *	-	Added NOWAYOUT support
26 *	4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>
27 *	-	Change comments
28 *	-	Eliminate fop_llseek
29 *	-	Change CONFIG_WATCHDOG_NOWAYOUT semantics
30 *	-	Add KERN_* tags to printks
31 *	-	fix possible wdt_is_open race
32 *	-	Report proper capabilities in watchdog_info
33 *	-	Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
34 *		GETTIMEOUT, SETOPTIONS} ioctls
35 *	09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>
36 *	-	cleanup of trailing spaces
37 *	-	added extra printk's for startup problems
38 *	-	use module_param
39 *	-	made timeout (the emulated heartbeat) a module_param
40 *	-	made the keepalive ping an internal subroutine
41 *	3/27 - 2004 Changes by Sean Young <sean@mess.org>
42 *	-	set MMCR_BASE to 0xfffef000
43 *	-	CBAR does not need to be read
44 *	-	removed debugging printks
45 *
46 *  This WDT driver is different from most other Linux WDT
47 *  drivers in that the driver will ping the watchdog by itself,
48 *  because this particular WDT has a very short timeout (1.6
49 *  seconds) and it would be insane to count on any userspace
50 *  daemon always getting scheduled within that time frame.
51 *
52 *  This driver uses memory mapped IO, and spinlock.
53 */
54
55#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
56
57#include <linux/module.h>
58#include <linux/moduleparam.h>
59#include <linux/types.h>
60#include <linux/timer.h>
61#include <linux/miscdevice.h>
62#include <linux/watchdog.h>
63#include <linux/fs.h>
64#include <linux/ioport.h>
65#include <linux/notifier.h>
66#include <linux/reboot.h>
67#include <linux/init.h>
68#include <linux/jiffies.h>
69#include <linux/io.h>
70#include <linux/uaccess.h>
71
72
73/*
74 * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
75 *
76 *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
77 *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
78 *
79 * We will program the SC520 watchdog for a timeout of 2.01s.
80 * If we reset the watchdog every ~250ms we should be safe.
81 */
82
83#define WDT_INTERVAL (HZ/4+1)
84
85/*
86 * We must not require too good response from the userspace daemon.
87 * Here we require the userspace daemon to send us a heartbeat
88 * char to /dev/watchdog every 30 seconds.
89 */
90
91#define WATCHDOG_TIMEOUT 30		/* 30 sec default timeout */
92/* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
93static int timeout = WATCHDOG_TIMEOUT;
94module_param(timeout, int, 0);
95MODULE_PARM_DESC(timeout,
96	"Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
97				__MODULE_STRING(WATCHDOG_TIMEOUT) ")");
98
99static bool nowayout = WATCHDOG_NOWAYOUT;
100module_param(nowayout, bool, 0);
101MODULE_PARM_DESC(nowayout,
102		"Watchdog cannot be stopped once started (default="
103				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
104
105/*
106 * AMD Elan SC520 - Watchdog Timer Registers
107 */
108#define MMCR_BASE	0xfffef000	/* The default base address */
109#define OFFS_WDTMRCTL	0xCB0	/* Watchdog Timer Control Register */
110
111/* WDT Control Register bit definitions */
112#define WDT_EXP_SEL_01	0x0001	/* [01] Time-out = 496 us (with 33 Mhz clk). */
113#define WDT_EXP_SEL_02	0x0002	/* [02] Time-out = 508 ms (with 33 Mhz clk). */
114#define WDT_EXP_SEL_03	0x0004	/* [03] Time-out = 1.02 s (with 33 Mhz clk). */
115#define WDT_EXP_SEL_04	0x0008	/* [04] Time-out = 2.03 s (with 33 Mhz clk). */
116#define WDT_EXP_SEL_05	0x0010	/* [05] Time-out = 4.07 s (with 33 Mhz clk). */
117#define WDT_EXP_SEL_06	0x0020	/* [06] Time-out = 8.13 s (with 33 Mhz clk). */
118#define WDT_EXP_SEL_07	0x0040	/* [07] Time-out = 16.27s (with 33 Mhz clk). */
119#define WDT_EXP_SEL_08	0x0080	/* [08] Time-out = 32.54s (with 33 Mhz clk). */
120#define WDT_IRQ_FLG	0x1000	/* [12] Interrupt Request Flag */
121#define WDT_WRST_ENB	0x4000	/* [14] Watchdog Timer Reset Enable */
122#define WDT_ENB		0x8000	/* [15] Watchdog Timer Enable */
123
124static __u16 __iomem *wdtmrctl;
125
126static void wdt_timer_ping(unsigned long);
127static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
128static unsigned long next_heartbeat;
129static unsigned long wdt_is_open;
130static char wdt_expect_close;
131static DEFINE_SPINLOCK(wdt_spinlock);
132
133/*
134 *	Whack the dog
135 */
136
137static void wdt_timer_ping(unsigned long data)
138{
139	/* If we got a heartbeat pulse within the WDT_US_INTERVAL
140	 * we agree to ping the WDT
141	 */
142	if (time_before(jiffies, next_heartbeat)) {
143		/* Ping the WDT */
144		spin_lock(&wdt_spinlock);
145		writew(0xAAAA, wdtmrctl);
146		writew(0x5555, wdtmrctl);
147		spin_unlock(&wdt_spinlock);
148
149		/* Re-set the timer interval */
150		mod_timer(&timer, jiffies + WDT_INTERVAL);
151	} else
152		pr_warn("Heartbeat lost! Will not ping the watchdog\n");
153}
154
155/*
156 *	Utility routines
157 */
158
159static void wdt_config(int writeval)
160{
161	unsigned long flags;
162
163	/* buy some time (ping) */
164	spin_lock_irqsave(&wdt_spinlock, flags);
165	readw(wdtmrctl);	/* ensure write synchronization */
166	writew(0xAAAA, wdtmrctl);
167	writew(0x5555, wdtmrctl);
168	/* unlock WDT = make WDT configuration register writable one time */
169	writew(0x3333, wdtmrctl);
170	writew(0xCCCC, wdtmrctl);
171	/* write WDT configuration register */
172	writew(writeval, wdtmrctl);
173	spin_unlock_irqrestore(&wdt_spinlock, flags);
174}
175
176static int wdt_startup(void)
177{
178	next_heartbeat = jiffies + (timeout * HZ);
179
180	/* Start the timer */
181	mod_timer(&timer, jiffies + WDT_INTERVAL);
182
183	/* Start the watchdog */
184	wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
185
186	pr_info("Watchdog timer is now enabled\n");
187	return 0;
188}
189
190static int wdt_turnoff(void)
191{
192	/* Stop the timer */
193	del_timer(&timer);
194
195	/* Stop the watchdog */
196	wdt_config(0);
197
198	pr_info("Watchdog timer is now disabled...\n");
199	return 0;
200}
201
202static int wdt_keepalive(void)
203{
204	/* user land ping */
205	next_heartbeat = jiffies + (timeout * HZ);
206	return 0;
207}
208
209static int wdt_set_heartbeat(int t)
210{
211	if ((t < 1) || (t > 3600))	/* arbitrary upper limit */
212		return -EINVAL;
213
214	timeout = t;
215	return 0;
216}
217
218/*
219 *	/dev/watchdog handling
220 */
221
222static ssize_t fop_write(struct file *file, const char __user *buf,
223						size_t count, loff_t *ppos)
224{
225	/* See if we got the magic character 'V' and reload the timer */
226	if (count) {
227		if (!nowayout) {
228			size_t ofs;
229
230			/* note: just in case someone wrote the magic character
231			 * five months ago... */
232			wdt_expect_close = 0;
233
234			/* now scan */
235			for (ofs = 0; ofs != count; ofs++) {
236				char c;
237				if (get_user(c, buf + ofs))
238					return -EFAULT;
239				if (c == 'V')
240					wdt_expect_close = 42;
241			}
242		}
243
244		/* Well, anyhow someone wrote to us, we should
245		   return that favour */
246		wdt_keepalive();
247	}
248	return count;
249}
250
251static int fop_open(struct inode *inode, struct file *file)
252{
253	/* Just in case we're already talking to someone... */
254	if (test_and_set_bit(0, &wdt_is_open))
255		return -EBUSY;
256	if (nowayout)
257		__module_get(THIS_MODULE);
258
259	/* Good, fire up the show */
260	wdt_startup();
261	return nonseekable_open(inode, file);
262}
263
264static int fop_close(struct inode *inode, struct file *file)
265{
266	if (wdt_expect_close == 42)
267		wdt_turnoff();
268	else {
269		pr_crit("Unexpected close, not stopping watchdog!\n");
270		wdt_keepalive();
271	}
272	clear_bit(0, &wdt_is_open);
273	wdt_expect_close = 0;
274	return 0;
275}
276
277static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
278{
279	void __user *argp = (void __user *)arg;
280	int __user *p = argp;
281	static const struct watchdog_info ident = {
282		.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
283							| WDIOF_MAGICCLOSE,
284		.firmware_version = 1,
285		.identity = "SC520",
286	};
287
288	switch (cmd) {
289	case WDIOC_GETSUPPORT:
290		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
291	case WDIOC_GETSTATUS:
292	case WDIOC_GETBOOTSTATUS:
293		return put_user(0, p);
294	case WDIOC_SETOPTIONS:
295	{
296		int new_options, retval = -EINVAL;
297
298		if (get_user(new_options, p))
299			return -EFAULT;
300
301		if (new_options & WDIOS_DISABLECARD) {
302			wdt_turnoff();
303			retval = 0;
304		}
305
306		if (new_options & WDIOS_ENABLECARD) {
307			wdt_startup();
308			retval = 0;
309		}
310
311		return retval;
312	}
313	case WDIOC_KEEPALIVE:
314		wdt_keepalive();
315		return 0;
316	case WDIOC_SETTIMEOUT:
317	{
318		int new_timeout;
319
320		if (get_user(new_timeout, p))
321			return -EFAULT;
322
323		if (wdt_set_heartbeat(new_timeout))
324			return -EINVAL;
325
326		wdt_keepalive();
327		/* Fall through */
328	}
329	case WDIOC_GETTIMEOUT:
330		return put_user(timeout, p);
331	default:
332		return -ENOTTY;
333	}
334}
335
336static const struct file_operations wdt_fops = {
337	.owner		= THIS_MODULE,
338	.llseek		= no_llseek,
339	.write		= fop_write,
340	.open		= fop_open,
341	.release	= fop_close,
342	.unlocked_ioctl	= fop_ioctl,
343};
344
345static struct miscdevice wdt_miscdev = {
346	.minor	= WATCHDOG_MINOR,
347	.name	= "watchdog",
348	.fops	= &wdt_fops,
349};
350
351/*
352 *	Notifier for system down
353 */
354
355static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
356	void *unused)
357{
358	if (code == SYS_DOWN || code == SYS_HALT)
359		wdt_turnoff();
360	return NOTIFY_DONE;
361}
362
363/*
364 *	The WDT needs to learn about soft shutdowns in order to
365 *	turn the timebomb registers off.
366 */
367
368static struct notifier_block wdt_notifier = {
369	.notifier_call = wdt_notify_sys,
370};
371
372static void __exit sc520_wdt_unload(void)
373{
374	if (!nowayout)
375		wdt_turnoff();
376
377	/* Deregister */
378	misc_deregister(&wdt_miscdev);
379	unregister_reboot_notifier(&wdt_notifier);
380	iounmap(wdtmrctl);
381}
382
383static int __init sc520_wdt_init(void)
384{
385	int rc = -EBUSY;
386
387	/* Check that the timeout value is within it's range ;
388	   if not reset to the default */
389	if (wdt_set_heartbeat(timeout)) {
390		wdt_set_heartbeat(WATCHDOG_TIMEOUT);
391		pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
392			WATCHDOG_TIMEOUT);
393	}
394
395	wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
396	if (!wdtmrctl) {
397		pr_err("Unable to remap memory\n");
398		rc = -ENOMEM;
399		goto err_out_region2;
400	}
401
402	rc = register_reboot_notifier(&wdt_notifier);
403	if (rc) {
404		pr_err("cannot register reboot notifier (err=%d)\n", rc);
405		goto err_out_ioremap;
406	}
407
408	rc = misc_register(&wdt_miscdev);
409	if (rc) {
410		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
411		       WATCHDOG_MINOR, rc);
412		goto err_out_notifier;
413	}
414
415	pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
416		timeout, nowayout);
417
418	return 0;
419
420err_out_notifier:
421	unregister_reboot_notifier(&wdt_notifier);
422err_out_ioremap:
423	iounmap(wdtmrctl);
424err_out_region2:
425	return rc;
426}
427
428module_init(sc520_wdt_init);
429module_exit(sc520_wdt_unload);
430
431MODULE_AUTHOR("Scott and Bill Jennings");
432MODULE_DESCRIPTION(
433	"Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
434MODULE_LICENSE("GPL");
435