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Linux/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 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 */
 80 static struct platform_device *acq_platform_device;
 81 static unsigned long acq_is_open;
 82 static char expect_close;
 83 
 84 /* module parameters */
 85 /* You must set this - there is no sane way to probe for this board. */
 86 static int wdt_stop = 0x43;
 87 module_param(wdt_stop, int, 0);
 88 MODULE_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. */
 91 static int wdt_start = 0x443;
 92 module_param(wdt_start, int, 0);
 93 MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");
 94 
 95 static bool nowayout = WATCHDOG_NOWAYOUT;
 96 module_param(nowayout, bool, 0);
 97 MODULE_PARM_DESC(nowayout,
 98         "Watchdog cannot be stopped once started (default="
 99         __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
100 
101 /*
102  *      Watchdog Operations
103  */
104 
105 static void acq_keepalive(void)
106 {
107         /* Write a watchdog value */
108         inb_p(wdt_start);
109 }
110 
111 static void acq_stop(void)
112 {
113         /* Turn the card off */
114         inb_p(wdt_stop);
115 }
116 
117 /*
118  *      /dev/watchdog handling
119  */
120 
121 static 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 
148 static 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 
193 static 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 
206 static 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 
223 static 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 
232 static struct miscdevice acq_miscdev = {
233         .minor  = WATCHDOG_MINOR,
234         .name   = "watchdog",
235         .fops   = &acq_fops,
236 };
237 
238 /*
239  *      Init & exit routines
240  */
241 
242 static 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;
268 unreg_regions:
269         release_region(wdt_start, 1);
270 unreg_stop:
271         if (wdt_stop != wdt_start)
272                 release_region(wdt_stop, 1);
273 out:
274         return ret;
275 }
276 
277 static 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 
287 static void acq_shutdown(struct platform_device *dev)
288 {
289         /* Turn the WDT off if we have a soft shutdown */
290         acq_stop();
291 }
292 
293 static struct platform_driver acquirewdt_driver = {
294         .remove         = acq_remove,
295         .shutdown       = acq_shutdown,
296         .driver         = {
297                 .owner  = THIS_MODULE,
298                 .name   = DRV_NAME,
299         },
300 };
301 
302 static int __init acq_init(void)
303 {
304         int err;
305 
306         pr_info("WDT driver for Acquire single board computer initialising\n");
307 
308         acq_platform_device = platform_device_register_simple(DRV_NAME,
309                                                                 -1, NULL, 0);
310         if (IS_ERR(acq_platform_device))
311                 return PTR_ERR(acq_platform_device);
312 
313         err = platform_driver_probe(&acquirewdt_driver, acq_probe);
314         if (err)
315                 goto unreg_platform_device;
316         return 0;
317 
318 unreg_platform_device:
319         platform_device_unregister(acq_platform_device);
320         return err;
321 }
322 
323 static void __exit acq_exit(void)
324 {
325         platform_device_unregister(acq_platform_device);
326         platform_driver_unregister(&acquirewdt_driver);
327         pr_info("Watchdog Module Unloaded\n");
328 }
329 
330 module_init(acq_init);
331 module_exit(acq_exit);
332 
333 MODULE_AUTHOR("David Woodhouse");
334 MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
335 MODULE_LICENSE("GPL");
336 

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