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 */ 76 static struct platform_device *acq_platform_device; 77 static unsigned long acq_is_open; 78 static char expect_close; 79 80 /* module parameters */ 81 /* You must set this - there is no sane way to probe for this board. */ 82 static int wdt_stop = 0x43; 83 module_param(wdt_stop, int, 0); 84 MODULE_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. */ 87 static int wdt_start = 0x443; 88 module_param(wdt_start, int, 0); 89 MODULE_PARM_DESC(wdt_start, "Acquire WDT 'start' io port (default 0x443)"); 90 91 static bool nowayout = WATCHDOG_NOWAYOUT; 92 module_param(nowayout, bool, 0); 93 MODULE_PARM_DESC(nowayout, 94 "Watchdog cannot be stopped once started (default=" 95 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")"); 96 97 /* 98 * Watchdog Operations 99 */ 100 101 static void acq_keepalive(void) 102 { 103 /* Write a watchdog value */ 104 inb_p(wdt_start); 105 } 106 107 static void acq_stop(void) 108 { 109 /* Turn the card off */ 110 inb_p(wdt_stop); 111 } 112 113 /* 114 * /dev/watchdog handling 115 */ 116 117 static 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 } 143 144 static 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 } 188 189 static 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 } 201 202 static 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 */ 218 219 static 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 }; 228 229 static struct miscdevice acq_miscdev = { 230 .minor = WATCHDOG_MINOR, 231 .name = "watchdog", 232 .fops = &acq_fops, 233 }; 234 235 /* 236 * Init & exit routines 237 */ 238 239 static 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; 265 unreg_regions: 266 release_region(wdt_start, 1); 267 unreg_stop: 268 if (wdt_stop != wdt_start) 269 release_region(wdt_stop, 1); 270 out: 271 return ret; 272 } 273 274 static int 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 return 0; 282 } 283 284 static void acq_shutdown(struct platform_device *dev) 285 { 286 /* Turn the WDT off if we have a soft shutdown */ 287 acq_stop(); 288 } 289 290 static struct platform_driver acquirewdt_driver = { 291 .remove = acq_remove, 292 .shutdown = acq_shutdown, 293 .driver = { 294 .name = DRV_NAME, 295 }, 296 }; 297 298 static int __init acq_init(void) 299 { 300 int err; 301 302 pr_info("WDT driver for Acquire single board computer initialising\n"); 303 304 acq_platform_device = platform_device_register_simple(DRV_NAME, 305 -1, NULL, 0); 306 if (IS_ERR(acq_platform_device)) 307 return PTR_ERR(acq_platform_device); 308 309 err = platform_driver_probe(&acquirewdt_driver, acq_probe); 310 if (err) 311 goto unreg_platform_device; 312 return 0; 313 314 unreg_platform_device: 315 platform_device_unregister(acq_platform_device); 316 return err; 317 } 318 319 static void __exit acq_exit(void) 320 { 321 platform_device_unregister(acq_platform_device); 322 platform_driver_unregister(&acquirewdt_driver); 323 pr_info("Watchdog Module Unloaded\n"); 324 } 325 326 module_init(acq_init); 327 module_exit(acq_exit); 328 329 MODULE_AUTHOR("David Woodhouse"); 330 MODULE_DESCRIPTION("Acquire Inc. Single Board Computer Watchdog Timer driver"); 331 MODULE_LICENSE("GPL"); 332