acquirewdt.c 8.3 KB

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  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. * Theory of Operation:
  22. * The Watch-Dog Timer is provided to ensure that standalone
  23. * Systems can always recover from catastrophic conditions that
  24. * caused the CPU to crash. This condition may have occurred by
  25. * external EMI or a software bug. When the CPU stops working
  26. * correctly, hardware on the board will either perform a hardware
  27. * reset (cold boot) or a non-maskable interrupt (NMI) to bring the
  28. * system back to a known state.
  29. *
  30. * The Watch-Dog Timer is controlled by two I/O Ports.
  31. * 443 hex - Read - Enable or refresh the Watch-Dog Timer
  32. * 043 hex - Read - Disable the Watch-Dog Timer
  33. *
  34. * To enable the Watch-Dog Timer, a read from I/O port 443h must
  35. * be performed. This will enable and activate the countdown timer
  36. * which will eventually time out and either reset the CPU or cause
  37. * an NMI depending on the setting of a jumper. To ensure that this
  38. * reset condition does not occur, the Watch-Dog Timer must be
  39. * periodically refreshed by reading the same I/O port 443h.
  40. * The Watch-Dog Timer is disabled by reading I/O port 043h.
  41. *
  42. * The Watch-Dog Timer Time-Out Period is set via jumpers.
  43. * It can be 1, 2, 10, 20, 110 or 220 seconds.
  44. */
  45. /*
  46. * Includes, defines, variables, module parameters, ...
  47. */
  48. #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  49. /* Includes */
  50. #include <linux/module.h> /* For module specific items */
  51. #include <linux/moduleparam.h> /* For new moduleparam's */
  52. #include <linux/types.h> /* For standard types (like size_t) */
  53. #include <linux/errno.h> /* For the -ENODEV/... values */
  54. #include <linux/kernel.h> /* For printk/panic/... */
  55. #include <linux/miscdevice.h> /* For struct miscdevice */
  56. #include <linux/watchdog.h> /* For the watchdog specific items */
  57. #include <linux/fs.h> /* For file operations */
  58. #include <linux/ioport.h> /* For io-port access */
  59. #include <linux/platform_device.h> /* For platform_driver framework */
  60. #include <linux/init.h> /* For __init/__exit/... */
  61. #include <linux/uaccess.h> /* For copy_to_user/put_user/... */
  62. #include <linux/io.h> /* For inb/outb/... */
  63. /* Module information */
  64. #define DRV_NAME "acquirewdt"
  65. #define WATCHDOG_NAME "Acquire WDT"
  66. /* There is no way to see what the correct time-out period is */
  67. #define WATCHDOG_HEARTBEAT 0
  68. /* internal variables */
  69. /* the watchdog platform device */
  70. static struct platform_device *acq_platform_device;
  71. static unsigned long acq_is_open;
  72. static char expect_close;
  73. /* module parameters */
  74. /* You must set this - there is no sane way to probe for this board. */
  75. static int wdt_stop = 0x43;
  76. module_param(wdt_stop, int, 0);
  77. MODULE_PARM_DESC(wdt_stop, "Acquire WDT 'stop' io port (default 0x43)");
  78. /* You must set this - there is no sane way to probe for this board. */
  79. static int wdt_start = 0x443;
  80. module_param(wdt_start, int, 0);
  81. MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)");
  82. static bool nowayout = WATCHDOG_NOWAYOUT;
  83. module_param(nowayout, bool, 0);
  84. MODULE_PARM_DESC(nowayout,
  85. "Watchdog cannot be stopped once started (default="
  86. __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  87. /*
  88. * Watchdog Operations
  89. */
  90. static void acq_keepalive(void)
  91. {
  92. /* Write a watchdog value */
  93. inb_p(wdt_start);
  94. }
  95. static void acq_stop(void)
  96. {
  97. /* Turn the card off */
  98. inb_p(wdt_stop);
  99. }
  100. /*
  101. * /dev/watchdog handling
  102. */
  103. static ssize_t acq_write(struct file *file, const char __user *buf,
  104. size_t count, loff_t *ppos)
  105. {
  106. /* See if we got the magic character 'V' and reload the timer */
  107. if (count) {
  108. if (!nowayout) {
  109. size_t i;
  110. /* note: just in case someone wrote the magic character
  111. five months ago... */
  112. expect_close = 0;
  113. /* scan to see whether or not we got the
  114. magic character */
  115. for (i = 0; i != count; i++) {
  116. char c;
  117. if (get_user(c, buf + i))
  118. return -EFAULT;
  119. if (c == 'V')
  120. expect_close = 42;
  121. }
  122. }
  123. /* Well, anyhow someone wrote to us, we should
  124. return that favour */
  125. acq_keepalive();
  126. }
  127. return count;
  128. }
  129. static long acq_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
  130. {
  131. int options, retval = -EINVAL;
  132. void __user *argp = (void __user *)arg;
  133. int __user *p = argp;
  134. static const struct watchdog_info ident = {
  135. .options = WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
  136. .firmware_version = 1,
  137. .identity = WATCHDOG_NAME,
  138. };
  139. switch (cmd) {
  140. case WDIOC_GETSUPPORT:
  141. return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
  142. case WDIOC_GETSTATUS:
  143. case WDIOC_GETBOOTSTATUS:
  144. return put_user(0, p);
  145. case WDIOC_SETOPTIONS:
  146. {
  147. if (get_user(options, p))
  148. return -EFAULT;
  149. if (options & WDIOS_DISABLECARD) {
  150. acq_stop();
  151. retval = 0;
  152. }
  153. if (options & WDIOS_ENABLECARD) {
  154. acq_keepalive();
  155. retval = 0;
  156. }
  157. return retval;
  158. }
  159. case WDIOC_KEEPALIVE:
  160. acq_keepalive();
  161. return 0;
  162. case WDIOC_GETTIMEOUT:
  163. return put_user(WATCHDOG_HEARTBEAT, p);
  164. default:
  165. return -ENOTTY;
  166. }
  167. }
  168. static int acq_open(struct inode *inode, struct file *file)
  169. {
  170. if (test_and_set_bit(0, &acq_is_open))
  171. return -EBUSY;
  172. if (nowayout)
  173. __module_get(THIS_MODULE);
  174. /* Activate */
  175. acq_keepalive();
  176. return stream_open(inode, file);
  177. }
  178. static int acq_close(struct inode *inode, struct file *file)
  179. {
  180. if (expect_close == 42) {
  181. acq_stop();
  182. } else {
  183. pr_crit("Unexpected close, not stopping watchdog!\n");
  184. acq_keepalive();
  185. }
  186. clear_bit(0, &acq_is_open);
  187. expect_close = 0;
  188. return 0;
  189. }
  190. /*
  191. * Kernel Interfaces
  192. */
  193. static const struct file_operations acq_fops = {
  194. .owner = THIS_MODULE,
  195. .llseek = no_llseek,
  196. .write = acq_write,
  197. .unlocked_ioctl = acq_ioctl,
  198. .compat_ioctl = compat_ptr_ioctl,
  199. .open = acq_open,
  200. .release = acq_close,
  201. };
  202. static struct miscdevice acq_miscdev = {
  203. .minor = WATCHDOG_MINOR,
  204. .name = "watchdog",
  205. .fops = &acq_fops,
  206. };
  207. /*
  208. * Init & exit routines
  209. */
  210. static int __init acq_probe(struct platform_device *dev)
  211. {
  212. int ret;
  213. if (wdt_stop != wdt_start) {
  214. if (!request_region(wdt_stop, 1, WATCHDOG_NAME)) {
  215. pr_err("I/O address 0x%04x already in use\n", wdt_stop);
  216. ret = -EIO;
  217. goto out;
  218. }
  219. }
  220. if (!request_region(wdt_start, 1, WATCHDOG_NAME)) {
  221. pr_err("I/O address 0x%04x already in use\n", wdt_start);
  222. ret = -EIO;
  223. goto unreg_stop;
  224. }
  225. ret = misc_register(&acq_miscdev);
  226. if (ret != 0) {
  227. pr_err("cannot register miscdev on minor=%d (err=%d)\n",
  228. WATCHDOG_MINOR, ret);
  229. goto unreg_regions;
  230. }
  231. pr_info("initialized. (nowayout=%d)\n", nowayout);
  232. return 0;
  233. unreg_regions:
  234. release_region(wdt_start, 1);
  235. unreg_stop:
  236. if (wdt_stop != wdt_start)
  237. release_region(wdt_stop, 1);
  238. out:
  239. return ret;
  240. }
  241. static int acq_remove(struct platform_device *dev)
  242. {
  243. misc_deregister(&acq_miscdev);
  244. release_region(wdt_start, 1);
  245. if (wdt_stop != wdt_start)
  246. release_region(wdt_stop, 1);
  247. return 0;
  248. }
  249. static void acq_shutdown(struct platform_device *dev)
  250. {
  251. /* Turn the WDT off if we have a soft shutdown */
  252. acq_stop();
  253. }
  254. static struct platform_driver acquirewdt_driver = {
  255. .remove = acq_remove,
  256. .shutdown = acq_shutdown,
  257. .driver = {
  258. .name = DRV_NAME,
  259. },
  260. };
  261. static int __init acq_init(void)
  262. {
  263. int err;
  264. pr_info("WDT driver for Acquire single board computer initialising\n");
  265. acq_platform_device = platform_device_register_simple(DRV_NAME,
  266. -1, NULL, 0);
  267. if (IS_ERR(acq_platform_device))
  268. return PTR_ERR(acq_platform_device);
  269. err = platform_driver_probe(&acquirewdt_driver, acq_probe);
  270. if (err)
  271. goto unreg_platform_device;
  272. return 0;
  273. unreg_platform_device:
  274. platform_device_unregister(acq_platform_device);
  275. return err;
  276. }
  277. static void __exit acq_exit(void)
  278. {
  279. platform_device_unregister(acq_platform_device);
  280. platform_driver_unregister(&acquirewdt_driver);
  281. pr_info("Watchdog Module Unloaded\n");
  282. }
  283. module_init(acq_init);
  284. module_exit(acq_exit);
  285. MODULE_AUTHOR("David Woodhouse");
  286. MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver");
  287. MODULE_LICENSE("GPL");