1/*
2 *	Acquire Single Board Computer Watchdog Timer driver
3 *
4 *	Based on wdt.c. Original copyright messages:
5 *
6 *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
7 *						All Rights Reserved.
8 *
9 *	This program is free software; you can redistribute it and/or
10 *	modify it under the terms of the GNU General Public License
11 *	as published by the Free Software Foundation; either version
12 *	2 of the License, or (at your option) any later version.
13 *
14 *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
15 *	warranty for any of this software. This material is provided
16 *	"AS-IS" and at no charge.
17 *
18 *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
19 *
20 *	14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
21 *	    Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
22 *	    Can't add timeout - driver doesn't allow changing value
23 */
24
25/*
26 *	Theory of Operation:
27 *		The Watch-Dog Timer is provided to ensure that standalone
28 *		Systems can always recover from catastrophic conditions that
29 *		caused the CPU to crash. This condition may have occurred by
30 *		external EMI or a software bug. When the CPU stops working
31 *		correctly, hardware on the board will either perform a hardware
32 *		reset (cold boot) or a non-maskable interrupt (NMI) to bring the
33 *		system back to a known state.
34 *
35 *		The Watch-Dog Timer is controlled by two I/O Ports.
36 *		  443 hex	- Read	- Enable or refresh the Watch-Dog Timer
37 *		  043 hex	- Read	- Disable the Watch-Dog Timer
38 *
39 *		To enable the Watch-Dog Timer, a read from I/O port 443h must
40 *		be performed. This will enable and activate the countdown timer
41 *		which will eventually time out and either reset the CPU or cause
42 *		an NMI depending on the setting of a jumper. To ensure that this
43 *		reset condition does not occur, the Watch-Dog Timer must be
44 *		periodically refreshed by reading the same I/O port 443h.
45 *		The Watch-Dog Timer is disabled by reading I/O port 043h.
46 *
47 *		The Watch-Dog Timer Time-Out Period is set via jumpers.
48 *		It can be 1, 2, 10, 20, 110 or 220 seconds.
49 */
50
51/*
52 *	Includes, defines, variables, module parameters, ...
53 */
54
55#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
56
57/* Includes */
58#include <linux/module.h>		/* For module specific items */
59#include <linux/moduleparam.h>		/* For new moduleparam's */
60#include <linux/types.h>		/* For standard types (like size_t) */
61#include <linux/errno.h>		/* For the -ENODEV/... values */
62#include <linux/kernel.h>		/* For printk/panic/... */
63#include <linux/miscdevice.h>		/* For struct miscdevice */
64#include <linux/watchdog.h>		/* For the watchdog specific items */
65#include <linux/fs.h>			/* For file operations */
66#include <linux/ioport.h>		/* For io-port access */
67#include <linux/platform_device.h>	/* For platform_driver framework */
68#include <linux/init.h>			/* For __init/__exit/... */
69#include <linux/uaccess.h>		/* For copy_to_user/put_user/... */
70#include <linux/io.h>			/* For inb/outb/... */
71
72/* Module information */
73#define DRV_NAME "acquirewdt"
74#define WATCHDOG_NAME "Acquire WDT"
75/* There is no way to see what the correct time-out period is */
76#define WATCHDOG_HEARTBEAT 0
77
78/* internal variables */
79/* the watchdog platform device */
80static struct platform_device *acq_platform_device;
81static unsigned long acq_is_open;
82static char expect_close;
83
84/* module parameters */
85/* You must set this - there is no sane way to probe for this board. */
86static int wdt_stop = 0x43;
87module_param(wdt_stop, int, 0);
88MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)");
89
90/* You must set this - there is no sane way to probe for this board. */
91static int wdt_start = 0x443;
92module_param(wdt_start, int, 0);
93MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");
94
95static bool nowayout = WATCHDOG_NOWAYOUT;
96module_param(nowayout, bool, 0);
97MODULE_PARM_DESC(nowayout,
98	"Watchdog cannot be stopped once started (default="
99	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
100
101/*
102 *	Watchdog Operations
103 */
104
105static void acq_keepalive(void)
106{
107	/* Write a watchdog value */
108	inb_p(wdt_start);
109}
110
111static void acq_stop(void)
112{
113	/* Turn the card off */
114	inb_p(wdt_stop);
115}
116
117/*
118 *	/dev/watchdog handling
119 */
120
121static ssize_t acq_write(struct file *file, const char __user *buf,
122						size_t count, loff_t *ppos)
123{
124	/* See if we got the magic character 'V' and reload the timer */
125	if (count) {
126		if (!nowayout) {
127			size_t i;
128			/* note: just in case someone wrote the magic character
129			   five months ago... */
130			expect_close = 0;
131			/* scan to see whether or not we got the
132			   magic character */
133			for (i = 0; i != count; i++) {
134				char c;
135				if (get_user(c, buf + i))
136					return -EFAULT;
137				if (c == 'V')
138					expect_close = 42;
139			}
140		}
141		/* Well, anyhow someone wrote to us, we should
142				return that favour */
143		acq_keepalive();
144	}
145	return count;
146}
147
148static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
149{
150	int options, retval = -EINVAL;
151	void __user *argp = (void __user *)arg;
152	int __user *p = argp;
153	static const struct watchdog_info ident = {
154		.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
155		.firmware_version = 1,
156		.identity = WATCHDOG_NAME,
157	};
158
159	switch (cmd) {
160	case WDIOC_GETSUPPORT:
161		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
162
163	case WDIOC_GETSTATUS:
164	case WDIOC_GETBOOTSTATUS:
165		return put_user(0, p);
166
167	case WDIOC_SETOPTIONS:
168	{
169		if (get_user(options, p))
170			return -EFAULT;
171		if (options & WDIOS_DISABLECARD) {
172			acq_stop();
173			retval = 0;
174		}
175		if (options & WDIOS_ENABLECARD) {
176			acq_keepalive();
177			retval = 0;
178		}
179		return retval;
180	}
181	case WDIOC_KEEPALIVE:
182		acq_keepalive();
183		return 0;
184
185	case WDIOC_GETTIMEOUT:
186		return put_user(WATCHDOG_HEARTBEAT, p);
187
188	default:
189		return -ENOTTY;
190	}
191}
192
193static int acq_open(struct inode *inode, struct file *file)
194{
195	if (test_and_set_bit(0, &acq_is_open))
196		return -EBUSY;
197
198	if (nowayout)
199		__module_get(THIS_MODULE);
200
201	/* Activate */
202	acq_keepalive();
203	return nonseekable_open(inode, file);
204}
205
206static int acq_close(struct inode *inode, struct file *file)
207{
208	if (expect_close == 42) {
209		acq_stop();
210	} else {
211		pr_crit("Unexpected close, not stopping watchdog!\n");
212		acq_keepalive();
213	}
214	clear_bit(0, &acq_is_open);
215	expect_close = 0;
216	return 0;
217}
218
219/*
220 *	Kernel Interfaces
221 */
222
223static const struct file_operations acq_fops = {
224	.owner		= THIS_MODULE,
225	.llseek		= no_llseek,
226	.write		= acq_write,
227	.unlocked_ioctl	= acq_ioctl,
228	.open		= acq_open,
229	.release	= acq_close,
230};
231
232static struct miscdevice acq_miscdev = {
233	.minor	= WATCHDOG_MINOR,
234	.name	= "watchdog",
235	.fops	= &acq_fops,
236};
237
238/*
239 *	Init & exit routines
240 */
241
242static int __init acq_probe(struct platform_device *dev)
243{
244	int ret;
245
246	if (wdt_stop != wdt_start) {
247		if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {
248			pr_err("I/O address 0x%04x already in use\n", wdt_stop);
249			ret = -EIO;
250			goto out;
251		}
252	}
253
254	if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
255		pr_err("I/O address 0x%04x already in use\n", wdt_start);
256		ret = -EIO;
257		goto unreg_stop;
258	}
259	ret = misc_register(&acq_miscdev);
260	if (ret != 0) {
261		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
262		       WATCHDOG_MINOR, ret);
263		goto unreg_regions;
264	}
265	pr_info("initialized. (nowayout=%d)\n", nowayout);
266
267	return 0;
268unreg_regions:
269	release_region(wdt_start, 1);
270unreg_stop:
271	if (wdt_stop != wdt_start)
272		release_region(wdt_stop, 1);
273out:
274	return ret;
275}
276
277static int acq_remove(struct platform_device *dev)
278{
279	misc_deregister(&acq_miscdev);
280	release_region(wdt_start, 1);
281	if (wdt_stop != wdt_start)
282		release_region(wdt_stop, 1);
283
284	return 0;
285}
286
287static void acq_shutdown(struct platform_device *dev)
288{
289	/* Turn the WDT off if we have a soft shutdown */
290	acq_stop();
291}
292
293static struct platform_driver acquirewdt_driver = {
294	.remove		= acq_remove,
295	.shutdown	= acq_shutdown,
296	.driver		= {
297		.name	= DRV_NAME,
298	},
299};
300
301static int __init acq_init(void)
302{
303	int err;
304
305	pr_info("WDT driver for Acquire single board computer initialising\n");
306
307	acq_platform_device = platform_device_register_simple(DRV_NAME,
308								-1, NULL, 0);
309	if (IS_ERR(acq_platform_device))
310		return PTR_ERR(acq_platform_device);
311
312	err = platform_driver_probe(&acquirewdt_driver, acq_probe);
313	if (err)
314		goto unreg_platform_device;
315	return 0;
316
317unreg_platform_device:
318	platform_device_unregister(acq_platform_device);
319	return err;
320}
321
322static void __exit acq_exit(void)
323{
324	platform_device_unregister(acq_platform_device);
325	platform_driver_unregister(&acquirewdt_driver);
326	pr_info("Watchdog Module Unloaded\n");
327}
328
329module_init(acq_init);
330module_exit(acq_exit);
331
332MODULE_AUTHOR("David Woodhouse");
333MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
334MODULE_LICENSE("GPL");
335