1// SPDX-License-Identifier: GPL-2.0+
2/*
3 *	Acquire Single Board Computer Watchdog Timer driver
4 *
5 *	Based on wdt.c. Original copyright messages:
6 *
7 *	(c) Copyright 1996 Alan Cox <alan@lxorguk.ukuu.org.uk>,
8 *						All Rights Reserved.
9 *
10 *	Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
11 *	warranty for any of this software. This material is provided
12 *	"AS-IS" and at no charge.
13 *
14 *	(c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
15 *
16 *	14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
17 *	    Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
18 *	    Can't add timeout - driver doesn't allow changing value
19 */
20
21/*
22 *	Theory of Operation:
23 *		The Watch-Dog Timer is provided to ensure that standalone
24 *		Systems can always recover from catastrophic conditions that
25 *		caused the CPU to crash. This condition may have occurred by
26 *		external EMI or a software bug. When the CPU stops working
27 *		correctly, hardware on the board will either perform a hardware
28 *		reset (cold boot) or a non-maskable interrupt (NMI) to bring the
29 *		system back to a known state.
30 *
31 *		The Watch-Dog Timer is controlled by two I/O Ports.
32 *		  443 hex	- Read	- Enable or refresh the Watch-Dog Timer
33 *		  043 hex	- Read	- Disable the Watch-Dog Timer
34 *
35 *		To enable the Watch-Dog Timer, a read from I/O port 443h must
36 *		be performed. This will enable and activate the countdown timer
37 *		which will eventually time out and either reset the CPU or cause
38 *		an NMI depending on the setting of a jumper. To ensure that this
39 *		reset condition does not occur, the Watch-Dog Timer must be
40 *		periodically refreshed by reading the same I/O port 443h.
41 *		The Watch-Dog Timer is disabled by reading I/O port 043h.
42 *
43 *		The Watch-Dog Timer Time-Out Period is set via jumpers.
44 *		It can be 1, 2, 10, 20, 110 or 220 seconds.
45 */
46
47/*
48 *	Includes, defines, variables, module parameters, ...
49 */
50
51#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
52
53/* Includes */
54#include <linux/module.h>		/* For module specific items */
55#include <linux/moduleparam.h>		/* For new moduleparam's */
56#include <linux/types.h>		/* For standard types (like size_t) */
57#include <linux/errno.h>		/* For the -ENODEV/... values */
58#include <linux/kernel.h>		/* For printk/panic/... */
59#include <linux/miscdevice.h>		/* For struct miscdevice */
60#include <linux/watchdog.h>		/* For the watchdog specific items */
61#include <linux/fs.h>			/* For file operations */
62#include <linux/ioport.h>		/* For io-port access */
63#include <linux/platform_device.h>	/* For platform_driver framework */
64#include <linux/init.h>			/* For __init/__exit/... */
65#include <linux/uaccess.h>		/* For copy_to_user/put_user/... */
66#include <linux/io.h>			/* For inb/outb/... */
67
68/* Module information */
69#define DRV_NAME "acquirewdt"
70#define WATCHDOG_NAME "Acquire WDT"
71/* There is no way to see what the correct time-out period is */
72#define WATCHDOG_HEARTBEAT 0
73
74/* internal variables */
75/* the watchdog platform device */
76static struct platform_device *acq_platform_device;
77static unsigned long acq_is_open;
78static char expect_close;
79
80/* module parameters */
81/* You must set this - there is no sane way to probe for this board. */
82static int wdt_stop = 0x43;
83module_param(wdt_stop, int, 0);
84MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)");
85
86/* You must set this - there is no sane way to probe for this board. */
87static int wdt_start = 0x443;
88module_param(wdt_start, int, 0);
89MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");
90
91static bool nowayout = WATCHDOG_NOWAYOUT;
92module_param(nowayout, bool, 0);
93MODULE_PARM_DESC(nowayout,
94	"Watchdog cannot be stopped once started (default="
95	__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
96
97/*
98 *	Watchdog Operations
99 */
100
101static void acq_keepalive(void)
102{
103	/* Write a watchdog value */
104	inb_p(wdt_start);
105}
106
107static void acq_stop(void)
108{
109	/* Turn the card off */
110	inb_p(wdt_stop);
111}
112
113/*
114 *	/dev/watchdog handling
115 */
116
117static ssize_t acq_write(struct file *file, const char __user *buf,
118						size_t count, loff_t *ppos)
119{
120	/* See if we got the magic character 'V' and reload the timer */
121	if (count) {
122		if (!nowayout) {
123			size_t i;
124			/* note: just in case someone wrote the magic character
125			   five months ago... */
126			expect_close = 0;
127			/* scan to see whether or not we got the
128			   magic character */
129			for (i = 0; i != count; i++) {
130				char c;
131				if (get_user(c, buf + i))
132					return -EFAULT;
133				if (c == 'V')
134					expect_close = 42;
135			}
136		}
137		/* Well, anyhow someone wrote to us, we should
138				return that favour */
139		acq_keepalive();
140	}
141	return count;
142}
143
144static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
145{
146	int options, retval = -EINVAL;
147	void __user *argp = (void __user *)arg;
148	int __user *p = argp;
149	static const struct watchdog_info ident = {
150		.options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
151		.firmware_version = 1,
152		.identity = WATCHDOG_NAME,
153	};
154
155	switch (cmd) {
156	case WDIOC_GETSUPPORT:
157		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
158
159	case WDIOC_GETSTATUS:
160	case WDIOC_GETBOOTSTATUS:
161		return put_user(0, p);
162
163	case WDIOC_SETOPTIONS:
164	{
165		if (get_user(options, p))
166			return -EFAULT;
167		if (options & WDIOS_DISABLECARD) {
168			acq_stop();
169			retval = 0;
170		}
171		if (options & WDIOS_ENABLECARD) {
172			acq_keepalive();
173			retval = 0;
174		}
175		return retval;
176	}
177	case WDIOC_KEEPALIVE:
178		acq_keepalive();
179		return 0;
180
181	case WDIOC_GETTIMEOUT:
182		return put_user(WATCHDOG_HEARTBEAT, p);
183
184	default:
185		return -ENOTTY;
186	}
187}
188
189static int acq_open(struct inode *inode, struct file *file)
190{
191	if (test_and_set_bit(0, &acq_is_open))
192		return -EBUSY;
193
194	if (nowayout)
195		__module_get(THIS_MODULE);
196
197	/* Activate */
198	acq_keepalive();
199	return stream_open(inode, file);
200}
201
202static int acq_close(struct inode *inode, struct file *file)
203{
204	if (expect_close == 42) {
205		acq_stop();
206	} else {
207		pr_crit("Unexpected close, not stopping watchdog!\n");
208		acq_keepalive();
209	}
210	clear_bit(0, &acq_is_open);
211	expect_close = 0;
212	return 0;
213}
214
215/*
216 *	Kernel Interfaces
217 */
218
219static const struct file_operations acq_fops = {
220	.owner		= THIS_MODULE,
221	.llseek		= no_llseek,
222	.write		= acq_write,
223	.unlocked_ioctl	= acq_ioctl,
224	.compat_ioctl	= compat_ptr_ioctl,
225	.open		= acq_open,
226	.release	= acq_close,
227};
228
229static struct miscdevice acq_miscdev = {
230	.minor	= WATCHDOG_MINOR,
231	.name	= "watchdog",
232	.fops	= &acq_fops,
233};
234
235/*
236 *	Init & exit routines
237 */
238
239static int __init acq_probe(struct platform_device *dev)
240{
241	int ret;
242
243	if (wdt_stop != wdt_start) {
244		if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {
245			pr_err("I/O address 0x%04x already in use\n", wdt_stop);
246			ret = -EIO;
247			goto out;
248		}
249	}
250
251	if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
252		pr_err("I/O address 0x%04x already in use\n", wdt_start);
253		ret = -EIO;
254		goto unreg_stop;
255	}
256	ret = misc_register(&acq_miscdev);
257	if (ret != 0) {
258		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
259		       WATCHDOG_MINOR, ret);
260		goto unreg_regions;
261	}
262	pr_info("initialized. (nowayout=%d)\n", nowayout);
263
264	return 0;
265unreg_regions:
266	release_region(wdt_start, 1);
267unreg_stop:
268	if (wdt_stop != wdt_start)
269		release_region(wdt_stop, 1);
270out:
271	return ret;
272}
273
274static void acq_remove(struct platform_device *dev)
275{
276	misc_deregister(&acq_miscdev);
277	release_region(wdt_start, 1);
278	if (wdt_stop != wdt_start)
279		release_region(wdt_stop, 1);
280}
281
282static void acq_shutdown(struct platform_device *dev)
283{
284	/* Turn the WDT off if we have a soft shutdown */
285	acq_stop();
286}
287
288static struct platform_driver acquirewdt_driver = {
289	.remove_new	= acq_remove,
290	.shutdown	= acq_shutdown,
291	.driver		= {
292		.name	= DRV_NAME,
293	},
294};
295
296static int __init acq_init(void)
297{
298	int err;
299
300	pr_info("WDT driver for Acquire single board computer initialising\n");
301
302	acq_platform_device = platform_device_register_simple(DRV_NAME,
303								-1, NULL, 0);
304	if (IS_ERR(acq_platform_device))
305		return PTR_ERR(acq_platform_device);
306
307	err = platform_driver_probe(&acquirewdt_driver, acq_probe);
308	if (err)
309		goto unreg_platform_device;
310	return 0;
311
312unreg_platform_device:
313	platform_device_unregister(acq_platform_device);
314	return err;
315}
316
317static void __exit acq_exit(void)
318{
319	platform_device_unregister(acq_platform_device);
320	platform_driver_unregister(&acquirewdt_driver);
321	pr_info("Watchdog Module Unloaded\n");
322}
323
324module_init(acq_init);
325module_exit(acq_exit);
326
327MODULE_AUTHOR("David Woodhouse");
328MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
329MODULE_LICENSE("GPL");
330