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 #ifdef CONFIG_WATCHDOG_NOWAYOUT
  79 static int nowayout = 1;
  80 #else
  81 static int nowayout = 0;
  82 #endif
  83
  84 /**
  85  *      sh_wdt_start - Start the Watchdog
  86  *
  87  *      Starts the watchdog.
  88  */
  89 static void sh_wdt_start(void)
  90 {
  91         __u8 csr;
  92
  93         next_heartbeat = jiffies + (heartbeat * HZ);
  94         mod_timer(&timer, next_ping_period(clock_division_ratio));
  95
  96         csr = sh_wdt_read_csr();
  97         csr |= WTCSR_WT | clock_division_ratio;
  98         sh_wdt_write_csr(csr);
  99
 100         sh_wdt_write_cnt(0);
 101
 102         /*
 103          * These processors have a bit of an inconsistent initialization
 104          * process.. starting with SH-3, RSTS was moved to WTCSR, and the
 105          * RSTCSR register was removed.
 106          *
 107          * On the SH-2 however, in addition with bits being in different
 108          * locations, we must deal with RSTCSR outright..
 109          */
 110         csr = sh_wdt_read_csr();
 111         csr |= WTCSR_TME;
 112         csr &= ~WTCSR_RSTS;
 113         sh_wdt_write_csr(csr);
 114
 115 #ifdef CONFIG_CPU_SH2
 116         /*
 117          * Whoever came up with the RSTCSR semantics must've been smoking
 118          * some of the good stuff, since in addition to the WTCSR/WTCNT write
 119          * brain-damage, it's managed to fuck things up one step further..
 120          *
 121          * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
 122          * but if we want to touch RSTE or RSTS, the upper byte has to be
 123          * 0x5a..
 124          */
 125         csr = sh_wdt_read_rstcsr();
 126         csr &= ~RSTCSR_RSTS;
 127         sh_wdt_write_rstcsr(csr);
 128 #endif
 129 }
 130
 131 /**
 132  *      sh_wdt_stop - Stop the Watchdog
 133  *
 134  *      Stops the watchdog.
 135  */
 136 static void sh_wdt_stop(void)
 137 {
 138         __u8 csr;
 139
 140         del_timer(&timer);
 141
 142         csr = sh_wdt_read_csr();
 143         csr &= ~WTCSR_TME;
 144         sh_wdt_write_csr(csr);
 145 }
 146
 147 /**
 148  *      sh_wdt_keepalive - Keep the Userspace Watchdog Alive
 149  *
 150  *      The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
 151  */
 152 static void sh_wdt_keepalive(void)
 153 {
 154         next_heartbeat = jiffies + (heartbeat * HZ);
 155 }
 156
 157 /**
 158  *      sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
 159  *
 160  *      Set the Userspace Watchdog heartbeat
 161  */
 162 static int sh_wdt_set_heartbeat(int t)
 163 {
 164         if ((t < 1) || (t > 3600)) /* arbitrary upper limit */
 165                 return -EINVAL;
 166
 167         heartbeat = t;
 168         return 0;
 169 }
 170
 171 /**
 172  *      sh_wdt_ping - Ping the Watchdog
 173  *
 174  *      @data: Unused
 175  *
 176  *      Clears overflow bit, resets timer counter.
 177  */
 178 static void sh_wdt_ping(unsigned long data)
 179 {
 180         if (time_before(jiffies, next_heartbeat)) {
 181                 __u8 csr;
 182
 183                 csr = sh_wdt_read_csr();
 184                 csr &= ~WTCSR_IOVF;
 185                 sh_wdt_write_csr(csr);
 186
 187                 sh_wdt_write_cnt(0);
 188
 189                 mod_timer(&timer, next_ping_period(clock_division_ratio));
 190         } else {
 191                 printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
 192         }
 193 }
 194
 195 /**
 196  *      sh_wdt_open - Open the Device
 197  *
 198  *      @inode: inode of device
 199  *      @file: file handle of device
 200  *
 201  *      Watchdog device is opened and started.
 202  */
 203 static int sh_wdt_open(struct inode *inode, struct file *file)
 204 {
 205         if (test_and_set_bit(0, &shwdt_is_open))
 206                 return -EBUSY;
 207         if (nowayout)
 208                 __module_get(THIS_MODULE);
 209
 210         sh_wdt_start();
 211
 212         return nonseekable_open(inode, file);
 213 }
 214
 215 /**
 216  *      sh_wdt_close - Close the Device
 217  *
 218  *      @inode: inode of device
 219  *      @file: file handle of device
 220  *
 221  *      Watchdog device is closed and stopped.
 222  */
 223 static int sh_wdt_close(struct inode *inode, struct file *file)
 224 {
 225         if (shwdt_expect_close == 42) {
 226                 sh_wdt_stop();
 227         } else {
 228                 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
 229                 sh_wdt_keepalive();
 230         }
 231
 232         clear_bit(0, &shwdt_is_open);
 233         shwdt_expect_close = 0;
 234
 235         return 0;
 236 }
 237
 238 /**
 239  *      sh_wdt_write - Write to Device
 240  *
 241  *      @file: file handle of device
 242  *      @buf: buffer to write
 243  *      @count: length of buffer
 244  *      @ppos: offset
 245  *
 246  *      Pings the watchdog on write.
 247  */
 248 static ssize_t sh_wdt_write(struct file *file, const char *buf,
 249                             size_t count, loff_t *ppos)
 250 {
 251         if (count) {
 252                 if (!nowayout) {
 253                         size_t i;
 254
 255                         shwdt_expect_close = 0;
 256
 257                         for (i = 0; i != count; i++) {
 258                                 char c;
 259                                 if (get_user(c, buf + i))
 260                                         return -EFAULT;
 261                                 if (c == 'V')
 262                                         shwdt_expect_close = 42;
 263                         }
 264                 }
 265                 sh_wdt_keepalive();
 266         }
 267
 268         return count;
 269 }
 270
 271 /**
 272  *      sh_wdt_ioctl - Query Device
 273  *
 274  *      @inode: inode of device
 275  *      @file: file handle of device
 276  *      @cmd: watchdog command
 277  *      @arg: argument
 278  *
 279  *      Query basic information from the device or ping it, as outlined by the
 280  *      watchdog API.
 281  */
 282 static int sh_wdt_ioctl(struct inode *inode, struct file *file,
 283                         unsigned int cmd, unsigned long arg)
 284 {
 285         int new_heartbeat;
 286         int options, retval = -EINVAL;
 287
 288         switch (cmd) {
 289                 case WDIOC_GETSUPPORT:
 290                         return copy_to_user((struct watchdog_info *)arg,
 291                                           &sh_wdt_info,
 292                                           sizeof(sh_wdt_info)) ? -EFAULT : 0;
 293                 case WDIOC_GETSTATUS:
 294                 case WDIOC_GETBOOTSTATUS:
 295                         return put_user(0, (int *)arg);
 296                 case WDIOC_KEEPALIVE:
 297                         sh_wdt_keepalive();
 298                         return 0;
 299                 case WDIOC_SETTIMEOUT:
 300                         if (get_user(new_heartbeat, (int *)arg))
 301                                 return -EFAULT;
 302
 303                         if (sh_wdt_set_heartbeat(new_heartbeat))
 304                                 return -EINVAL;
 305
 306                         sh_wdt_keepalive();
 307                         /* Fall */
 308                 case WDIOC_GETTIMEOUT:
 309                         return put_user(heartbeat, (int *)arg);
 310                 case WDIOC_SETOPTIONS:
 311                         if (get_user(options, (int *)arg))
 312                                 return -EFAULT;
 313
 314                         if (options & WDIOS_DISABLECARD) {
 315                                 sh_wdt_stop();
 316                                 retval = 0;
 317                         }
 318
 319                         if (options & WDIOS_ENABLECARD) {
 320                                 sh_wdt_start();
 321                                 retval = 0;
 322                         }
 323
 324                         return retval;
 325                 default:
 326                         return -ENOIOCTLCMD;
 327         }
 328
 329         return 0;
 330 }
 331
 332 /**
 333  *      sh_wdt_notify_sys - Notifier Handler
 334  *
 335  *      @this: notifier block
 336  *      @code: notifier event
 337  *      @unused: unused
 338  *
 339  *      Handles specific events, such as turning off the watchdog during a
 340  *      shutdown event.
 341  */
 342 static int sh_wdt_notify_sys(struct notifier_block *this,
 343                              unsigned long code, void *unused)
 344 {
 345         if (code == SYS_DOWN || code == SYS_HALT) {
 346                 sh_wdt_stop();
 347         }
 348
 349         return NOTIFY_DONE;
 350 }
 351
 352 static struct file_operations sh_wdt_fops = {
 353         .owner          = THIS_MODULE,
 354         .llseek         = no_llseek,
 355         .write          = sh_wdt_write,
 356         .ioctl          = sh_wdt_ioctl,
 357         .open           = sh_wdt_open,
 358         .release        = sh_wdt_close,
 359 };
 360
 361 static struct watchdog_info sh_wdt_info = {
 362         .options                = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
 363         .firmware_version       = 1,
 364         .identity               = "SH WDT",
 365 };
 366
 367 static struct notifier_block sh_wdt_notifier = {
 368         .notifier_call          = sh_wdt_notify_sys,
 369 };
 370
 371 static struct miscdevice sh_wdt_miscdev = {
 372         .minor          = WATCHDOG_MINOR,
 373         .name           = "watchdog",
 374         .fops           = &sh_wdt_fops,
 375 };
 376
 377 /**
 378  *      sh_wdt_init - Initialize module
 379  *
 380  *      Registers the device and notifier handler. Actual device
 381  *      initialization is handled by sh_wdt_open().
 382  */
 383 static int __init sh_wdt_init(void)
 384 {
 385         int rc;
 386
 387         if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {
 388                 clock_division_ratio = WTCSR_CKS_4096;
 389                 printk(KERN_INFO PFX "clock_division_ratio value must be 0x5<=x<=0x7, using %d\n",
 390                         clock_division_ratio);
 391         }
 392
 393         if (sh_wdt_set_heartbeat(heartbeat))
 394         {
 395                 heartbeat = WATCHDOG_HEARTBEAT;
 396                 printk(KERN_INFO PFX "heartbeat value must be 1<=x<=3600, using %d\n",
 397                         heartbeat);
 398         }
 399
 400         init_timer(&timer);
 401         timer.function = sh_wdt_ping;
 402         timer.data = 0;
 403
 404         rc = register_reboot_notifier(&sh_wdt_notifier);
 405         if (rc) {
 406                 printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n", rc);
 407                 return rc;
 408         }
 409
 410         rc = misc_register(&sh_wdt_miscdev);
 411         if (rc) {
 412                 printk(KERN_ERR PFX "Can't register miscdev on minor=%d (err=%d)\n",
 413                         sh_wdt_miscdev.minor, rc);
 414                 unregister_reboot_notifier(&sh_wdt_notifier);
 415                 return rc;
 416         }
 417
 418         printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
 419                 heartbeat, nowayout);
 420
 421         return 0;
 422 }
 423
 424 /**
 425  *      sh_wdt_exit - Deinitialize module
 426  *
 427  *      Unregisters the device and notifier handler. Actual device
 428  *      deinitialization is handled by sh_wdt_close().
 429  */
 430 static void __exit sh_wdt_exit(void)
 431 {
 432         misc_deregister(&sh_wdt_miscdev);
 433         unregister_reboot_notifier(&sh_wdt_notifier);
 434 }
 435
 436 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
 437 MODULE_DESCRIPTION("SuperH watchdog driver");
 438 MODULE_LICENSE("GPL");
 439 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 440
 441 module_param(clock_division_ratio, int, 0);
 442 MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). Defaults to 0x7.");
 443
 444 module_param(heartbeat, int, 0);
 445 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
 446
 447 module_param(nowayout, int, 0);
 448 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");
 449
 450 module_init(sh_wdt_init);
 451 module_exit(sh_wdt_exit);
 452