1/*
2 * drivers/char/watchdog/shwdt.c
3 *
4 * Watchdog driver for integrated watchdog in the SuperH processors.
5 *
6 * Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>
7 *
8 * This program is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License as published by the
10 * Free Software Foundation; either version 2 of the License, or (at your
11 * option) any later version.
12 *
13 * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
14 *     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
15 *
16 * 19-Apr-2002 Rob Radez <rob@osinvestor.com>
17 *     Added expect close support, made emulated timeout runtime changeable
18 *     general cleanups, add some ioctls
19 */
20#include <linux/module.h>
21#include <linux/moduleparam.h>
22#include <linux/init.h>
23#include <linux/types.h>
24#include <linux/miscdevice.h>
25#include <linux/watchdog.h>
26#include <linux/reboot.h>
27#include <linux/notifier.h>
28#include <linux/ioport.h>
29#include <linux/fs.h>
30#include <linux/mm.h>
31#include <asm/io.h>
32#include <asm/uaccess.h>
33#include <asm/watchdog.h>
34
35#define PFX "shwdt: "
36
37/*
38 * Default clock division ratio is 5.25 msecs. For an additional table of
39 * values, consult the asm-sh/watchdog.h. Overload this at module load
40 * time.
41 *
42 * In order for this to work reliably we need to have HZ set to 1000 or
43 * something quite higher than 100 (or we need a proper high-res timer
44 * implementation that will deal with this properly), otherwise the 10ms
45 * resolution of a jiffy is enough to trigger the overflow. For things like
46 * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
47 * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
48 * necssary.
49 *
50 * As a result of this timing problem, the only modes that are particularly
51 * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
52 * overflow periods respectively.
53 *
54 * Also, since we can't really expect userspace to be responsive enough
55 * before the overflow happens, we maintain two seperate timers .. One in
56 * the kernel for clearing out WOVF every 2ms or so (again, this depends on
57 * HZ == 1000), and another for monitoring userspace writes to the WDT device.
58 *
59 * As such, we currently use a configurable heartbeat interval which defaults
60 * to 30s. In this case, the userspace daemon is only responsible for periodic
61 * writes to the device before the next heartbeat is scheduled. If the daemon
62 * misses its deadline, the kernel timer will allow the WDT to overflow.
63 */
64static int clock_division_ratio = WTCSR_CKS_4096;
65
66#define next_ping_period(cks)	msecs_to_jiffies(cks - 4)
67
68static void sh_wdt_ping(unsigned long data);
69
70static unsigned long shwdt_is_open;
71static struct watchdog_info sh_wdt_info;
72static char shwdt_expect_close;
73static DEFINE_TIMER(timer, sh_wdt_ping, 0, 0);
74static unsigned long next_heartbeat;
75
76#define WATCHDOG_HEARTBEAT 30			/* 30 sec default heartbeat */
77static int heartbeat = WATCHDOG_HEARTBEAT;	/* in seconds */
78
79static int nowayout = WATCHDOG_NOWAYOUT;
80
81/**
82 * 	sh_wdt_start - Start the Watchdog
83 *
84 * 	Starts the watchdog.
85 */
86static void sh_wdt_start(void)
87{
88	__u8 csr;
89
90	next_heartbeat = jiffies + (heartbeat * HZ);
91	mod_timer(&timer, next_ping_period(clock_division_ratio));
92
93	csr = sh_wdt_read_csr();
94	csr |= WTCSR_WT | clock_division_ratio;
95	sh_wdt_write_csr(csr);
96
97	sh_wdt_write_cnt(0);
98
99	/*
100	 * These processors have a bit of an inconsistent initialization
101	 * process.. starting with SH-3, RSTS was moved to WTCSR, and the
102	 * RSTCSR register was removed.
103	 *
104	 * On the SH-2 however, in addition with bits being in different
105	 * locations, we must deal with RSTCSR outright..
106	 */
107	csr = sh_wdt_read_csr();
108	csr |= WTCSR_TME;
109	csr &= ~WTCSR_RSTS;
110	sh_wdt_write_csr(csr);
111
112#ifdef CONFIG_CPU_SH2
113	/*
114	 * Whoever came up with the RSTCSR semantics must've been smoking
115	 * some of the good stuff, since in addition to the WTCSR/WTCNT write
116	 * brain-damage, it's managed to fuck things up one step further..
117	 *
118	 * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
119	 * but if we want to touch RSTE or RSTS, the upper byte has to be
120	 * 0x5a..
121	 */
122	csr = sh_wdt_read_rstcsr();
123	csr &= ~RSTCSR_RSTS;
124	sh_wdt_write_rstcsr(csr);
125#endif
126}
127
128/**
129 * 	sh_wdt_stop - Stop the Watchdog
130 * 	Stops the watchdog.
131 */
132static void sh_wdt_stop(void)
133{
134	__u8 csr;
135
136	del_timer(&timer);
137
138	csr = sh_wdt_read_csr();
139	csr &= ~WTCSR_TME;
140	sh_wdt_write_csr(csr);
141}
142
143/**
144 * 	sh_wdt_keepalive - Keep the Userspace Watchdog Alive
145 * 	The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
146 */
147static inline void sh_wdt_keepalive(void)
148{
149	next_heartbeat = jiffies + (heartbeat * HZ);
150}
151
152/**
153 * 	sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
154 * 	Set the Userspace Watchdog heartbeat
155 */
156static int sh_wdt_set_heartbeat(int t)
157{
158	if (unlikely((t < 1) || (t > 3600))) /* arbitrary upper limit */
159		return -EINVAL;
160
161	heartbeat = t;
162	return 0;
163}
164
165/**
166 * 	sh_wdt_ping - Ping the Watchdog
167 *	@data: Unused
168 *
169 * 	Clears overflow bit, resets timer counter.
170 */
171static void sh_wdt_ping(unsigned long data)
172{
173	if (time_before(jiffies, next_heartbeat)) {
174		__u8 csr;
175
176		csr = sh_wdt_read_csr();
177		csr &= ~WTCSR_IOVF;
178		sh_wdt_write_csr(csr);
179
180		sh_wdt_write_cnt(0);
181
182		mod_timer(&timer, next_ping_period(clock_division_ratio));
183	} else
184		printk(KERN_WARNING PFX "Heartbeat lost! Will not ping "
185		       "the watchdog\n");
186}
187
188/**
189 * 	sh_wdt_open - Open the Device
190 * 	@inode: inode of device
191 * 	@file: file handle of device
192 *
193 * 	Watchdog device is opened and started.
194 */
195static int sh_wdt_open(struct inode *inode, struct file *file)
196{
197	if (test_and_set_bit(0, &shwdt_is_open))
198		return -EBUSY;
199	if (nowayout)
200		__module_get(THIS_MODULE);
201
202	sh_wdt_start();
203
204	return nonseekable_open(inode, file);
205}
206
207/**
208 * 	sh_wdt_close - Close the Device
209 * 	@inode: inode of device
210 * 	@file: file handle of device
211 *
212 * 	Watchdog device is closed and stopped.
213 */
214static int sh_wdt_close(struct inode *inode, struct file *file)
215{
216	if (shwdt_expect_close == 42) {
217		sh_wdt_stop();
218	} else {
219		printk(KERN_CRIT PFX "Unexpected close, not "
220		       "stopping watchdog!\n");
221		sh_wdt_keepalive();
222	}
223
224	clear_bit(0, &shwdt_is_open);
225	shwdt_expect_close = 0;
226
227	return 0;
228}
229
230/**
231 * 	sh_wdt_write - Write to Device
232 * 	@file: file handle of device
233 * 	@buf: buffer to write
234 * 	@count: length of buffer
235 * 	@ppos: offset
236 *
237 * 	Pings the watchdog on write.
238 */
239static ssize_t sh_wdt_write(struct file *file, const char *buf,
240			    size_t count, loff_t *ppos)
241{
242	if (count) {
243		if (!nowayout) {
244			size_t i;
245
246			shwdt_expect_close = 0;
247
248			for (i = 0; i != count; i++) {
249				char c;
250				if (get_user(c, buf + i))
251					return -EFAULT;
252				if (c == 'V')
253					shwdt_expect_close = 42;
254			}
255		}
256		sh_wdt_keepalive();
257	}
258
259	return count;
260}
261
262/**
263 * 	sh_wdt_mmap - map WDT/CPG registers into userspace
264 * 	@file: file structure for the device
265 * 	@vma: VMA to map the registers into
266 *
267 * 	A simple mmap() implementation for the corner cases where the counter
268 * 	needs to be mapped in userspace directly. Due to the relatively small
269 * 	size of the area, neighbouring registers not necessarily tied to the
270 * 	CPG will also be accessible through the register page, so this remains
271 * 	configurable for users that really know what they're doing.
272 *
273 *	Additionaly, the register page maps in the CPG register base relative
274 *	to the nearest page-aligned boundary, which requires that userspace do
275 *	the appropriate CPU subtype math for calculating the page offset for
276 *	the counter value.
277 */
278static int sh_wdt_mmap(struct file *file, struct vm_area_struct *vma)
279{
280	int ret = -ENOSYS;
281
282#ifdef CONFIG_SH_WDT_MMAP
283	unsigned long addr;
284
285	/* Only support the simple cases where we map in a register page. */
286	if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
287		return -EINVAL;
288
289	/*
290	 * Pick WTCNT as the start, it's usually the first register after the
291	 * FRQCR, and neither one are generally page-aligned out of the box.
292	 */
293	addr = WTCNT & ~(PAGE_SIZE - 1);
294
295	vma->vm_flags |= VM_IO;
296	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
297
298	if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,
299			       PAGE_SIZE, vma->vm_page_prot)) {
300		printk(KERN_ERR PFX "%s: io_remap_pfn_range failed\n",
301		       __FUNCTION__);
302		return -EAGAIN;
303	}
304
305	ret = 0;
306#endif
307
308	return ret;
309}
310
311/**
312 * 	sh_wdt_ioctl - Query Device
313 * 	@inode: inode of device
314 * 	@file: file handle of device
315 * 	@cmd: watchdog command
316 * 	@arg: argument
317 *
318 * 	Query basic information from the device or ping it, as outlined by the
319 * 	watchdog API.
320 */
321static int sh_wdt_ioctl(struct inode *inode, struct file *file,
322			unsigned int cmd, unsigned long arg)
323{
324	int new_heartbeat;
325	int options, retval = -EINVAL;
326
327	switch (cmd) {
328		case WDIOC_GETSUPPORT:
329			return copy_to_user((struct watchdog_info *)arg,
330					  &sh_wdt_info,
331					  sizeof(sh_wdt_info)) ? -EFAULT : 0;
332		case WDIOC_GETSTATUS:
333		case WDIOC_GETBOOTSTATUS:
334			return put_user(0, (int *)arg);
335		case WDIOC_KEEPALIVE:
336			sh_wdt_keepalive();
337			return 0;
338		case WDIOC_SETTIMEOUT:
339			if (get_user(new_heartbeat, (int *)arg))
340				return -EFAULT;
341
342			if (sh_wdt_set_heartbeat(new_heartbeat))
343				return -EINVAL;
344
345			sh_wdt_keepalive();
346			/* Fall */
347		case WDIOC_GETTIMEOUT:
348			return put_user(heartbeat, (int *)arg);
349		case WDIOC_SETOPTIONS:
350			if (get_user(options, (int *)arg))
351				return -EFAULT;
352
353			if (options & WDIOS_DISABLECARD) {
354				sh_wdt_stop();
355				retval = 0;
356			}
357
358			if (options & WDIOS_ENABLECARD) {
359				sh_wdt_start();
360				retval = 0;
361			}
362
363			return retval;
364		default:
365			return -ENOTTY;
366	}
367
368	return 0;
369}
370
371/**
372 * 	sh_wdt_notify_sys - Notifier Handler
373 * 	@this: notifier block
374 * 	@code: notifier event
375 * 	@unused: unused
376 *
377 * 	Handles specific events, such as turning off the watchdog during a
378 * 	shutdown event.
379 */
380static int sh_wdt_notify_sys(struct notifier_block *this,
381			     unsigned long code, void *unused)
382{
383	if (code == SYS_DOWN || code == SYS_HALT)
384		sh_wdt_stop();
385
386	return NOTIFY_DONE;
387}
388
389static const struct file_operations sh_wdt_fops = {
390	.owner		= THIS_MODULE,
391	.llseek		= no_llseek,
392	.write		= sh_wdt_write,
393	.ioctl		= sh_wdt_ioctl,
394	.open		= sh_wdt_open,
395	.release	= sh_wdt_close,
396	.mmap		= sh_wdt_mmap,
397};
398
399static struct watchdog_info sh_wdt_info = {
400	.options		= WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
401				  WDIOF_MAGICCLOSE,
402	.firmware_version	= 1,
403	.identity		= "SH WDT",
404};
405
406static struct notifier_block sh_wdt_notifier = {
407	.notifier_call		= sh_wdt_notify_sys,
408};
409
410static struct miscdevice sh_wdt_miscdev = {
411	.minor		= WATCHDOG_MINOR,
412	.name		= "watchdog",
413	.fops		= &sh_wdt_fops,
414};
415
416/**
417 * 	sh_wdt_init - Initialize module
418 * 	Registers the device and notifier handler. Actual device
419 * 	initialization is handled by sh_wdt_open().
420 */
421static int __init sh_wdt_init(void)
422{
423	int rc;
424
425	if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {
426		clock_division_ratio = WTCSR_CKS_4096;
427		printk(KERN_INFO PFX "clock_division_ratio value must "
428		       "be 0x5<=x<=0x7, using %d\n", clock_division_ratio);
429	}
430
431	rc = sh_wdt_set_heartbeat(heartbeat);
432	if (unlikely(rc)) {
433		heartbeat = WATCHDOG_HEARTBEAT;
434		printk(KERN_INFO PFX "heartbeat value must "
435		       "be 1<=x<=3600, using %d\n", heartbeat);
436	}
437
438	rc = register_reboot_notifier(&sh_wdt_notifier);
439	if (unlikely(rc)) {
440		printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n",
441		       rc);
442		return rc;
443	}
444
445	rc = misc_register(&sh_wdt_miscdev);
446	if (unlikely(rc)) {
447		printk(KERN_ERR PFX "Can't register miscdev on "
448		       "minor=%d (err=%d)\n", sh_wdt_miscdev.minor, rc);
449		unregister_reboot_notifier(&sh_wdt_notifier);
450		return rc;
451	}
452
453	printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
454		heartbeat, nowayout);
455
456	return 0;
457}
458
459/**
460 * 	sh_wdt_exit - Deinitialize module
461 * 	Unregisters the device and notifier handler. Actual device
462 * 	deinitialization is handled by sh_wdt_close().
463 */
464static void __exit sh_wdt_exit(void)
465{
466	misc_deregister(&sh_wdt_miscdev);
467	unregister_reboot_notifier(&sh_wdt_notifier);
468}
469
470MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
471MODULE_DESCRIPTION("SuperH watchdog driver");
472MODULE_LICENSE("GPL");
473MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
474
475module_param(clock_division_ratio, int, 0);
476MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). (default=" __MODULE_STRING(clock_division_ratio) ")");
477
478module_param(heartbeat, int, 0);
479MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
480
481module_param(nowayout, int, 0);
482MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
483
484module_init(sh_wdt_init);
485module_exit(sh_wdt_exit);
486