Root/drivers/watchdog/acquirewdt.c

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 MODULE_ALIAS_MISCDEV
64                            (WATCHDOG_MINOR) */
65#include <linux/watchdog.h> /* For the watchdog specific items */
66#include <linux/fs.h> /* For file operations */
67#include <linux/ioport.h> /* For io-port access */
68#include <linux/platform_device.h> /* For platform_driver framework */
69#include <linux/init.h> /* For __init/__exit/... */
70#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
71#include <linux/io.h> /* For inb/outb/... */
72
73/* Module information */
74#define DRV_NAME "acquirewdt"
75#define WATCHDOG_NAME "Acquire WDT"
76/* There is no way to see what the correct time-out period is */
77#define WATCHDOG_HEARTBEAT 0
78
79/* internal variables */
80/* the watchdog platform device */
81static struct platform_device *acq_platform_device;
82static unsigned long acq_is_open;
83static char expect_close;
84
85/* module parameters */
86/* You must set this - there is no sane way to probe for this board. */
87static int wdt_stop = 0x43;
88module_param(wdt_stop, int, 0);
89MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)");
90
91/* You must set this - there is no sane way to probe for this board. */
92static int wdt_start = 0x443;
93module_param(wdt_start, int, 0);
94MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");
95
96static bool nowayout = WATCHDOG_NOWAYOUT;
97module_param(nowayout, bool, 0);
98MODULE_PARM_DESC(nowayout,
99    "Watchdog cannot be stopped once started (default="
100    __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
101
102/*
103 * Watchdog Operations
104 */
105
106static void acq_keepalive(void)
107{
108    /* Write a watchdog value */
109    inb_p(wdt_start);
110}
111
112static void acq_stop(void)
113{
114    /* Turn the card off */
115    inb_p(wdt_stop);
116}
117
118/*
119 * /dev/watchdog handling
120 */
121
122static ssize_t acq_write(struct file *file, const char __user *buf,
123                        size_t count, loff_t *ppos)
124{
125    /* See if we got the magic character 'V' and reload the timer */
126    if (count) {
127        if (!nowayout) {
128            size_t i;
129            /* note: just in case someone wrote the magic character
130               five months ago... */
131            expect_close = 0;
132            /* scan to see whether or not we got the
133               magic character */
134            for (i = 0; i != count; i++) {
135                char c;
136                if (get_user(c, buf + i))
137                    return -EFAULT;
138                if (c == 'V')
139                    expect_close = 42;
140            }
141        }
142        /* Well, anyhow someone wrote to us, we should
143                return that favour */
144        acq_keepalive();
145    }
146    return count;
147}
148
149static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
150{
151    int options, retval = -EINVAL;
152    void __user *argp = (void __user *)arg;
153    int __user *p = argp;
154    static const struct watchdog_info ident = {
155        .options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
156        .firmware_version = 1,
157        .identity = WATCHDOG_NAME,
158    };
159
160    switch (cmd) {
161    case WDIOC_GETSUPPORT:
162        return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
163
164    case WDIOC_GETSTATUS:
165    case WDIOC_GETBOOTSTATUS:
166        return put_user(0, p);
167
168    case WDIOC_SETOPTIONS:
169    {
170        if (get_user(options, p))
171            return -EFAULT;
172        if (options & WDIOS_DISABLECARD) {
173            acq_stop();
174            retval = 0;
175        }
176        if (options & WDIOS_ENABLECARD) {
177            acq_keepalive();
178            retval = 0;
179        }
180        return retval;
181    }
182    case WDIOC_KEEPALIVE:
183        acq_keepalive();
184        return 0;
185
186    case WDIOC_GETTIMEOUT:
187        return put_user(WATCHDOG_HEARTBEAT, p);
188
189    default:
190        return -ENOTTY;
191    }
192}
193
194static int acq_open(struct inode *inode, struct file *file)
195{
196    if (test_and_set_bit(0, &acq_is_open))
197        return -EBUSY;
198
199    if (nowayout)
200        __module_get(THIS_MODULE);
201
202    /* Activate */
203    acq_keepalive();
204    return nonseekable_open(inode, file);
205}
206
207static int acq_close(struct inode *inode, struct file *file)
208{
209    if (expect_close == 42) {
210        acq_stop();
211    } else {
212        pr_crit("Unexpected close, not stopping watchdog!\n");
213        acq_keepalive();
214    }
215    clear_bit(0, &acq_is_open);
216    expect_close = 0;
217    return 0;
218}
219
220/*
221 * Kernel Interfaces
222 */
223
224static const struct file_operations acq_fops = {
225    .owner = THIS_MODULE,
226    .llseek = no_llseek,
227    .write = acq_write,
228    .unlocked_ioctl = acq_ioctl,
229    .open = acq_open,
230    .release = acq_close,
231};
232
233static struct miscdevice acq_miscdev = {
234    .minor = WATCHDOG_MINOR,
235    .name = "watchdog",
236    .fops = &acq_fops,
237};
238
239/*
240 * Init & exit routines
241 */
242
243static int __devinit acq_probe(struct platform_device *dev)
244{
245    int ret;
246
247    if (wdt_stop != wdt_start) {
248        if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {
249            pr_err("I/O address 0x%04x already in use\n", wdt_stop);
250            ret = -EIO;
251            goto out;
252        }
253    }
254
255    if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
256        pr_err("I/O address 0x%04x already in use\n", wdt_start);
257        ret = -EIO;
258        goto unreg_stop;
259    }
260    ret = misc_register(&acq_miscdev);
261    if (ret != 0) {
262        pr_err("cannot register miscdev on minor=%d (err=%d)\n",
263               WATCHDOG_MINOR, ret);
264        goto unreg_regions;
265    }
266    pr_info("initialized. (nowayout=%d)\n", nowayout);
267
268    return 0;
269unreg_regions:
270    release_region(wdt_start, 1);
271unreg_stop:
272    if (wdt_stop != wdt_start)
273        release_region(wdt_stop, 1);
274out:
275    return ret;
276}
277
278static int __devexit acq_remove(struct platform_device *dev)
279{
280    misc_deregister(&acq_miscdev);
281    release_region(wdt_start, 1);
282    if (wdt_stop != wdt_start)
283        release_region(wdt_stop, 1);
284
285    return 0;
286}
287
288static void acq_shutdown(struct platform_device *dev)
289{
290    /* Turn the WDT off if we have a soft shutdown */
291    acq_stop();
292}
293
294static struct platform_driver acquirewdt_driver = {
295    .probe = acq_probe,
296    .remove = __devexit_p(acq_remove),
297    .shutdown = acq_shutdown,
298    .driver = {
299        .owner = THIS_MODULE,
300        .name = DRV_NAME,
301    },
302};
303
304static int __init acq_init(void)
305{
306    int err;
307
308    pr_info("WDT driver for Acquire single board computer initialising\n");
309
310    err = platform_driver_register(&acquirewdt_driver);
311    if (err)
312        return err;
313
314    acq_platform_device = platform_device_register_simple(DRV_NAME,
315                                -1, NULL, 0);
316    if (IS_ERR(acq_platform_device)) {
317        err = PTR_ERR(acq_platform_device);
318        goto unreg_platform_driver;
319    }
320    return 0;
321
322unreg_platform_driver:
323    platform_driver_unregister(&acquirewdt_driver);
324    return err;
325}
326
327static void __exit acq_exit(void)
328{
329    platform_device_unregister(acq_platform_device);
330    platform_driver_unregister(&acquirewdt_driver);
331    pr_info("Watchdog Module Unloaded\n");
332}
333
334module_init(acq_init);
335module_exit(acq_exit);
336
337MODULE_AUTHOR("David Woodhouse");
338MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
339MODULE_LICENSE("GPL");
340MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
341

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