drivers/char/watchdog/shwdt.c

   1 /*
   2  * drivers/char/watchdog/shwdt.c
   3  *
   4  * Watchdog driver for integrated watchdog in the SuperH processors.
   5  *
   6  * Copyright (C) 2001, 2002, 2003 Paul Mundt <lethal@linux-sh.org>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the
  10  * Free Software Foundation; either version 2 of the License, or (at your
  11  * option) any later version.
  12  *
  13  * 14-Dec-2001 Matt Domsch <Matt_Domsch@dell.com>
  14  *     Added nowayout module option to override CONFIG_WATCHDOG_NOWAYOUT
  15  *
  16  * 19-Apr-2002 Rob Radez <rob@osinvestor.com>
  17  *     Added expect close support, made emulated timeout runtime changeable
  18  *     general cleanups, add some ioctls
  19  */
  20 #include <linux/config.h>
  21 #include <linux/module.h>
  22 #include <linux/moduleparam.h>
  23 #include <linux/init.h>
  24 #include <linux/types.h>
  25 #include <linux/miscdevice.h>
  26 #include <linux/watchdog.h>
  27 #include <linux/reboot.h>
  28 #include <linux/notifier.h>
  29 #include <linux/ioport.h>
  30 #include <linux/fs.h>
  31
  32 #include <asm/io.h>
  33 #include <asm/uaccess.h>
  34 #include <asm/watchdog.h>
  35
  36 #define PFX "shwdt: "
  37
  38 /*
  39  * Default clock division ratio is 5.25 msecs. For an additional table of
  40  * values, consult the asm-sh/watchdog.h. Overload this at module load
  41  * time.
  42  *
  43  * In order for this to work reliably we need to have HZ set to 1000 or
  44  * something quite higher than 100 (or we need a proper high-res timer
  45  * implementation that will deal with this properly), otherwise the 10ms
  46  * resolution of a jiffy is enough to trigger the overflow. For things like
  47  * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
  48  * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
  49  * necssary.
  50  *
  51  * As a result of this timing problem, the only modes that are particularly
  52  * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
  53  * overflow periods respectively.
  54  *
  55  * Also, since we can't really expect userspace to be responsive enough
  56  * before the overflow happens, we maintain two seperate timers .. One in
  57  * the kernel for clearing out WOVF every 2ms or so (again, this depends on
  58  * HZ == 1000), and another for monitoring userspace writes to the WDT device.
  59  *
  60  * As such, we currently use a configurable heartbeat interval which defaults
  61  * to 30s. In this case, the userspace daemon is only responsible for periodic
  62  * writes to the device before the next heartbeat is scheduled. If the daemon
  63  * misses its deadline, the kernel timer will allow the WDT to overflow.
  64  */
  65 static int clock_division_ratio = WTCSR_CKS_4096;
  66
  67 #define next_ping_period(cks)   msecs_to_jiffies(cks - 4)
  68
  69 static unsigned long shwdt_is_open;
  70 static struct watchdog_info sh_wdt_info;
  71 static char shwdt_expect_close;
  72 static struct timer_list timer;
  73 static unsigned long next_heartbeat;
  74
  75 #define WATCHDOG_HEARTBEAT 30                   /* 30 sec default heartbeat */
  76 static int heartbeat = WATCHDOG_HEARTBEAT;      /* in seconds */
  77
  78 static int nowayout = WATCHDOG_NOWAYOUT;
  79
  80 /**
  81  *      sh_wdt_start - Start the Watchdog
  82  *
  83  *      Starts the watchdog.
  84  */
  85 static void sh_wdt_start(void)
  86 {
  87         __u8 csr;
  88
  89         next_heartbeat = jiffies + (heartbeat * HZ);
  90         mod_timer(&timer, next_ping_period(clock_division_ratio));
  91
  92         csr = sh_wdt_read_csr();
  93         csr |= WTCSR_WT | clock_division_ratio;
  94         sh_wdt_write_csr(csr);
  95
  96         sh_wdt_write_cnt(0);
  97
  98         /*
  99          * These processors have a bit of an inconsistent initialization
 100          * process.. starting with SH-3, RSTS was moved to WTCSR, and the
 101          * RSTCSR register was removed.
 102          *
 103          * On the SH-2 however, in addition with bits being in different
 104          * locations, we must deal with RSTCSR outright..
 105          */
 106         csr = sh_wdt_read_csr();
 107         csr |= WTCSR_TME;
 108         csr &= ~WTCSR_RSTS;
 109         sh_wdt_write_csr(csr);
 110
 111 #ifdef CONFIG_CPU_SH2
 112         /*
 113          * Whoever came up with the RSTCSR semantics must've been smoking
 114          * some of the good stuff, since in addition to the WTCSR/WTCNT write
 115          * brain-damage, it's managed to fuck things up one step further..
 116          *
 117          * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
 118          * but if we want to touch RSTE or RSTS, the upper byte has to be
 119          * 0x5a..
 120          */
 121         csr = sh_wdt_read_rstcsr();
 122         csr &= ~RSTCSR_RSTS;
 123         sh_wdt_write_rstcsr(csr);
 124 #endif
 125 }
 126
 127 /**
 128  *      sh_wdt_stop - Stop the Watchdog
 129  *
 130  *      Stops the watchdog.
 131  */
 132 static void sh_wdt_stop(void)
 133 {
 134         __u8 csr;
 135
 136         del_timer(&timer);
 137
 138         csr = sh_wdt_read_csr();
 139         csr &= ~WTCSR_TME;
 140         sh_wdt_write_csr(csr);
 141 }
 142
 143 /**
 144  *      sh_wdt_keepalive - Keep the Userspace Watchdog Alive
 145  *
 146  *      The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
 147  */
 148 static void sh_wdt_keepalive(void)
 149 {
 150         next_heartbeat = jiffies + (heartbeat * HZ);
 151 }
 152
 153 /**
 154  *      sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
 155  *
 156  *      Set the Userspace Watchdog heartbeat
 157  */
 158 static int sh_wdt_set_heartbeat(int t)
 159 {
 160         if ((t < 1) || (t > 3600)) /* arbitrary upper limit */
 161                 return -EINVAL;
 162
 163         heartbeat = t;
 164         return 0;
 165 }
 166
 167 /**
 168  *      sh_wdt_ping - Ping the Watchdog
 169  *
 170  *      @data: Unused
 171  *
 172  *      Clears overflow bit, resets timer counter.
 173  */
 174 static void sh_wdt_ping(unsigned long data)
 175 {
 176         if (time_before(jiffies, next_heartbeat)) {
 177                 __u8 csr;
 178
 179                 csr = sh_wdt_read_csr();
 180                 csr &= ~WTCSR_IOVF;
 181                 sh_wdt_write_csr(csr);
 182
 183                 sh_wdt_write_cnt(0);
 184
 185                 mod_timer(&timer, next_ping_period(clock_division_ratio));
 186         } else {
 187                 printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
 188         }
 189 }
 190
 191 /**
 192  *      sh_wdt_open - Open the Device
 193  *
 194  *      @inode: inode of device
 195  *      @file: file handle of device
 196  *
 197  *      Watchdog device is opened and started.
 198  */
 199 static int sh_wdt_open(struct inode *inode, struct file *file)
 200 {
 201         if (test_and_set_bit(0, &shwdt_is_open))
 202                 return -EBUSY;
 203         if (nowayout)
 204                 __module_get(THIS_MODULE);
 205
 206         sh_wdt_start();
 207
 208         return nonseekable_open(inode, file);
 209 }
 210
 211 /**
 212  *      sh_wdt_close - Close the Device
 213  *
 214  *      @inode: inode of device
 215  *      @file: file handle of device
 216  *
 217  *      Watchdog device is closed and stopped.
 218  */
 219 static int sh_wdt_close(struct inode *inode, struct file *file)
 220 {
 221         if (shwdt_expect_close == 42) {
 222                 sh_wdt_stop();
 223         } else {
 224                 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
 225                 sh_wdt_keepalive();
 226         }
 227
 228         clear_bit(0, &shwdt_is_open);
 229         shwdt_expect_close = 0;
 230
 231         return 0;
 232 }
 233
 234 /**
 235  *      sh_wdt_write - Write to Device
 236  *
 237  *      @file: file handle of device
 238  *      @buf: buffer to write
 239  *      @count: length of buffer
 240  *      @ppos: offset
 241  *
 242  *      Pings the watchdog on write.
 243  */
 244 static ssize_t sh_wdt_write(struct file *file, const char *buf,
 245                             size_t count, loff_t *ppos)
 246 {
 247         if (count) {
 248                 if (!nowayout) {
 249                         size_t i;
 250
 251                         shwdt_expect_close = 0;
 252
 253                         for (i = 0; i != count; i++) {
 254                                 char c;
 255                                 if (get_user(c, buf + i))
 256                                         return -EFAULT;
 257                                 if (c == 'V')
 258                                         shwdt_expect_close = 42;
 259                         }
 260                 }
 261                 sh_wdt_keepalive();
 262         }
 263
 264         return count;
 265 }
 266
 267 /**
 268  *      sh_wdt_ioctl - Query Device
 269  *
 270  *      @inode: inode of device
 271  *      @file: file handle of device
 272  *      @cmd: watchdog command
 273  *      @arg: argument
 274  *
 275  *      Query basic information from the device or ping it, as outlined by the
 276  *      watchdog API.
 277  */
 278 static int sh_wdt_ioctl(struct inode *inode, struct file *file,
 279                         unsigned int cmd, unsigned long arg)
 280 {
 281         int new_heartbeat;
 282         int options, retval = -EINVAL;
 283
 284         switch (cmd) {
 285                 case WDIOC_GETSUPPORT:
 286                         return copy_to_user((struct watchdog_info *)arg,
 287                                           &sh_wdt_info,
 288                                           sizeof(sh_wdt_info)) ? -EFAULT : 0;
 289                 case WDIOC_GETSTATUS:
 290                 case WDIOC_GETBOOTSTATUS:
 291                         return put_user(0, (int *)arg);
 292                 case WDIOC_KEEPALIVE:
 293                         sh_wdt_keepalive();
 294                         return 0;
 295                 case WDIOC_SETTIMEOUT:
 296                         if (get_user(new_heartbeat, (int *)arg))
 297                                 return -EFAULT;
 298
 299                         if (sh_wdt_set_heartbeat(new_heartbeat))
 300                                 return -EINVAL;
 301
 302                         sh_wdt_keepalive();
 303                         /* Fall */
 304                 case WDIOC_GETTIMEOUT:
 305                         return put_user(heartbeat, (int *)arg);
 306                 case WDIOC_SETOPTIONS:
 307                         if (get_user(options, (int *)arg))
 308                                 return -EFAULT;
 309
 310                         if (options & WDIOS_DISABLECARD) {
 311                                 sh_wdt_stop();
 312                                 retval = 0;
 313                         }
 314
 315                         if (options & WDIOS_ENABLECARD) {
 316                                 sh_wdt_start();
 317                                 retval = 0;
 318                         }
 319
 320                         return retval;
 321                 default:
 322                         return -ENOIOCTLCMD;
 323         }
 324
 325         return 0;
 326 }
 327
 328 /**
 329  *      sh_wdt_notify_sys - Notifier Handler
 330  *
 331  *      @this: notifier block
 332  *      @code: notifier event
 333  *      @unused: unused
 334  *
 335  *      Handles specific events, such as turning off the watchdog during a
 336  *      shutdown event.
 337  */
 338 static int sh_wdt_notify_sys(struct notifier_block *this,
 339                              unsigned long code, void *unused)
 340 {
 341         if (code == SYS_DOWN || code == SYS_HALT) {
 342                 sh_wdt_stop();
 343         }
 344
 345         return NOTIFY_DONE;
 346 }
 347
 348 static struct file_operations sh_wdt_fops = {
 349         .owner          = THIS_MODULE,
 350         .llseek         = no_llseek,
 351         .write          = sh_wdt_write,
 352         .ioctl          = sh_wdt_ioctl,
 353         .open           = sh_wdt_open,
 354         .release        = sh_wdt_close,
 355 };
 356
 357 static struct watchdog_info sh_wdt_info = {
 358         .options                = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
 359         .firmware_version       = 1,
 360         .identity               = "SH WDT",
 361 };
 362
 363 static struct notifier_block sh_wdt_notifier = {
 364         .notifier_call          = sh_wdt_notify_sys,
 365 };
 366
 367 static struct miscdevice sh_wdt_miscdev = {
 368         .minor          = WATCHDOG_MINOR,
 369         .name           = "watchdog",
 370         .fops           = &sh_wdt_fops,
 371 };
 372
 373 /**
 374  *      sh_wdt_init - Initialize module
 375  *
 376  *      Registers the device and notifier handler. Actual device
 377  *      initialization is handled by sh_wdt_open().
 378  */
 379 static int __init sh_wdt_init(void)
 380 {
 381         int rc;
 382
 383         if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {
 384                 clock_division_ratio = WTCSR_CKS_4096;
 385                 printk(KERN_INFO PFX "clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
 386                         clock_division_ratio);
 387         }
 388
 389         if (sh_wdt_set_heartbeat(heartbeat))
 390         {
 391                 heartbeat = WATCHDOG_HEARTBEAT;
 392                 printk(KERN_INFO PFX "heartbeat value must be 1<=x<=3600, using %d\n",
 393                         heartbeat);
 394         }
 395
 396         init_timer(&timer);
 397         timer.function = sh_wdt_ping;
 398         timer.data = 0;
 399
 400         rc = register_reboot_notifier(&sh_wdt_notifier);
 401         if (rc) {
 402                 printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n", rc);
 403                 return rc;
 404         }
 405
 406         rc = misc_register(&sh_wdt_miscdev);
 407         if (rc) {
 408                 printk(KERN_ERR PFX "Can't register miscdev on minor=%d (err=%d)\n",
 409                         sh_wdt_miscdev.minor, rc);
 410                 unregister_reboot_notifier(&sh_wdt_notifier);
 411                 return rc;
 412         }
 413
 414         printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
 415                 heartbeat, nowayout);
 416
 417         return 0;
 418 }
 419
 420 /**
 421  *      sh_wdt_exit - Deinitialize module
 422  *
 423  *      Unregisters the device and notifier handler. Actual device
 424  *      deinitialization is handled by sh_wdt_close().
 425  */
 426 static void __exit sh_wdt_exit(void)
 427 {
 428         misc_deregister(&sh_wdt_miscdev);
 429         unregister_reboot_notifier(&sh_wdt_notifier);
 430 }
 431
 432 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
 433 MODULE_DESCRIPTION("SuperH watchdog driver");
 434 MODULE_LICENSE("GPL");
 435 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 436
 437 module_param(clock_division_ratio, int, 0);
 438 MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). Defaults to 0x7.");
 439
 440 module_param(heartbeat, int, 0);
 441 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
 442
 443 module_param(nowayout, int, 0);
 444 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
 445
 446 module_init(sh_wdt_init);
 447 module_exit(sh_wdt_exit);
 448