drivers/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/module.h>
  21 #include <linux/moduleparam.h>
  22 #include <linux/init.h>
  23 #include <linux/types.h>
  24 #include <linux/miscdevice.h>
  25 #include <linux/watchdog.h>
  26 #include <linux/reboot.h>
  27 #include <linux/notifier.h>
  28 #include <linux/ioport.h>
  29 #include <linux/fs.h>
  30 #include <linux/mm.h>
  31 #include <asm/io.h>
  32 #include <asm/uaccess.h>
  33 #include <asm/watchdog.h>
  34
  35 #define PFX "shwdt: "
  36
  37 /*
  38  * Default clock division ratio is 5.25 msecs. For an additional table of
  39  * values, consult the asm-sh/watchdog.h. Overload this at module load
  40  * time.
  41  *
  42  * In order for this to work reliably we need to have HZ set to 1000 or
  43  * something quite higher than 100 (or we need a proper high-res timer
  44  * implementation that will deal with this properly), otherwise the 10ms
  45  * resolution of a jiffy is enough to trigger the overflow. For things like
  46  * the SH-4 and SH-5, this isn't necessarily that big of a problem, though
  47  * for the SH-2 and SH-3, this isn't recommended unless the WDT is absolutely
  48  * necssary.
  49  *
  50  * As a result of this timing problem, the only modes that are particularly
  51  * feasible are the 4096 and the 2048 divisors, which yeild 5.25 and 2.62ms
  52  * overflow periods respectively.
  53  *
  54  * Also, since we can't really expect userspace to be responsive enough
  55  * before the overflow happens, we maintain two seperate timers .. One in
  56  * the kernel for clearing out WOVF every 2ms or so (again, this depends on
  57  * HZ == 1000), and another for monitoring userspace writes to the WDT device.
  58  *
  59  * As such, we currently use a configurable heartbeat interval which defaults
  60  * to 30s. In this case, the userspace daemon is only responsible for periodic
  61  * writes to the device before the next heartbeat is scheduled. If the daemon
  62  * misses its deadline, the kernel timer will allow the WDT to overflow.
  63  */
  64 static int clock_division_ratio = WTCSR_CKS_4096;
  65
  66 #define next_ping_period(cks)   msecs_to_jiffies(cks - 4)
  67
  68 static void sh_wdt_ping(unsigned long data);
  69
  70 static unsigned long shwdt_is_open;
  71 static struct watchdog_info sh_wdt_info;
  72 static char shwdt_expect_close;
  73 static DEFINE_TIMER(timer, sh_wdt_ping, 0, 0);
  74 static unsigned long next_heartbeat;
  75
  76 #define WATCHDOG_HEARTBEAT 30                   /* 30 sec default heartbeat */
  77 static int heartbeat = WATCHDOG_HEARTBEAT;      /* in seconds */
  78
  79 static int nowayout = WATCHDOG_NOWAYOUT;
  80
  81 /**
  82  *      sh_wdt_start - Start the Watchdog
  83  *
  84  *      Starts the watchdog.
  85  */
  86 static void sh_wdt_start(void)
  87 {
  88         __u8 csr;
  89
  90         next_heartbeat = jiffies + (heartbeat * HZ);
  91         mod_timer(&timer, next_ping_period(clock_division_ratio));
  92
  93         csr = sh_wdt_read_csr();
  94         csr |= WTCSR_WT | clock_division_ratio;
  95         sh_wdt_write_csr(csr);
  96
  97         sh_wdt_write_cnt(0);
  98
  99         /*
 100          * These processors have a bit of an inconsistent initialization
 101          * process.. starting with SH-3, RSTS was moved to WTCSR, and the
 102          * RSTCSR register was removed.
 103          *
 104          * On the SH-2 however, in addition with bits being in different
 105          * locations, we must deal with RSTCSR outright..
 106          */
 107         csr = sh_wdt_read_csr();
 108         csr |= WTCSR_TME;
 109         csr &= ~WTCSR_RSTS;
 110         sh_wdt_write_csr(csr);
 111
 112 #ifdef CONFIG_CPU_SH2
 113         /*
 114          * Whoever came up with the RSTCSR semantics must've been smoking
 115          * some of the good stuff, since in addition to the WTCSR/WTCNT write
 116          * brain-damage, it's managed to fuck things up one step further..
 117          *
 118          * If we need to clear the WOVF bit, the upper byte has to be 0xa5..
 119          * but if we want to touch RSTE or RSTS, the upper byte has to be
 120          * 0x5a..
 121          */
 122         csr = sh_wdt_read_rstcsr();
 123         csr &= ~RSTCSR_RSTS;
 124         sh_wdt_write_rstcsr(csr);
 125 #endif
 126 }
 127
 128 /**
 129  *      sh_wdt_stop - Stop the Watchdog
 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  *      The Userspace watchdog got a KeepAlive: schedule the next heartbeat.
 146  */
 147 static inline void sh_wdt_keepalive(void)
 148 {
 149         next_heartbeat = jiffies + (heartbeat * HZ);
 150 }
 151
 152 /**
 153  *      sh_wdt_set_heartbeat - Set the Userspace Watchdog heartbeat
 154  *      Set the Userspace Watchdog heartbeat
 155  */
 156 static int sh_wdt_set_heartbeat(int t)
 157 {
 158         if (unlikely((t < 1) || (t > 3600))) /* arbitrary upper limit */
 159                 return -EINVAL;
 160
 161         heartbeat = t;
 162         return 0;
 163 }
 164
 165 /**
 166  *      sh_wdt_ping - Ping the Watchdog
 167  *      @data: Unused
 168  *
 169  *      Clears overflow bit, resets timer counter.
 170  */
 171 static void sh_wdt_ping(unsigned long data)
 172 {
 173         if (time_before(jiffies, next_heartbeat)) {
 174                 __u8 csr;
 175
 176                 csr = sh_wdt_read_csr();
 177                 csr &= ~WTCSR_IOVF;
 178                 sh_wdt_write_csr(csr);
 179
 180                 sh_wdt_write_cnt(0);
 181
 182                 mod_timer(&timer, next_ping_period(clock_division_ratio));
 183         } else
 184                 printk(KERN_WARNING PFX "Heartbeat lost! Will not ping "
 185                        "the watchdog\n");
 186 }
 187
 188 /**
 189  *      sh_wdt_open - Open the Device
 190  *      @inode: inode of device
 191  *      @file: file handle of device
 192  *
 193  *      Watchdog device is opened and started.
 194  */
 195 static int sh_wdt_open(struct inode *inode, struct file *file)
 196 {
 197         if (test_and_set_bit(0, &shwdt_is_open))
 198                 return -EBUSY;
 199         if (nowayout)
 200                 __module_get(THIS_MODULE);
 201
 202         sh_wdt_start();
 203
 204         return nonseekable_open(inode, file);
 205 }
 206
 207 /**
 208  *      sh_wdt_close - Close the Device
 209  *      @inode: inode of device
 210  *      @file: file handle of device
 211  *
 212  *      Watchdog device is closed and stopped.
 213  */
 214 static int sh_wdt_close(struct inode *inode, struct file *file)
 215 {
 216         if (shwdt_expect_close == 42) {
 217                 sh_wdt_stop();
 218         } else {
 219                 printk(KERN_CRIT PFX "Unexpected close, not "
 220                        "stopping watchdog!\n");
 221                 sh_wdt_keepalive();
 222         }
 223
 224         clear_bit(0, &shwdt_is_open);
 225         shwdt_expect_close = 0;
 226
 227         return 0;
 228 }
 229
 230 /**
 231  *      sh_wdt_write - Write to Device
 232  *      @file: file handle of device
 233  *      @buf: buffer to write
 234  *      @count: length of buffer
 235  *      @ppos: offset
 236  *
 237  *      Pings the watchdog on write.
 238  */
 239 static ssize_t sh_wdt_write(struct file *file, const char *buf,
 240                             size_t count, loff_t *ppos)
 241 {
 242         if (count) {
 243                 if (!nowayout) {
 244                         size_t i;
 245
 246                         shwdt_expect_close = 0;
 247
 248                         for (i = 0; i != count; i++) {
 249                                 char c;
 250                                 if (get_user(c, buf + i))
 251                                         return -EFAULT;
 252                                 if (c == 'V')
 253                                         shwdt_expect_close = 42;
 254                         }
 255                 }
 256                 sh_wdt_keepalive();
 257         }
 258
 259         return count;
 260 }
 261
 262 /**
 263  *      sh_wdt_mmap - map WDT/CPG registers into userspace
 264  *      @file: file structure for the device
 265  *      @vma: VMA to map the registers into
 266  *
 267  *      A simple mmap() implementation for the corner cases where the counter
 268  *      needs to be mapped in userspace directly. Due to the relatively small
 269  *      size of the area, neighbouring registers not necessarily tied to the
 270  *      CPG will also be accessible through the register page, so this remains
 271  *      configurable for users that really know what they're doing.
 272  *
 273  *      Additionaly, the register page maps in the CPG register base relative
 274  *      to the nearest page-aligned boundary, which requires that userspace do
 275  *      the appropriate CPU subtype math for calculating the page offset for
 276  *      the counter value.
 277  */
 278 static int sh_wdt_mmap(struct file *file, struct vm_area_struct *vma)
 279 {
 280         int ret = -ENOSYS;
 281
 282 #ifdef CONFIG_SH_WDT_MMAP
 283         unsigned long addr;
 284
 285         /* Only support the simple cases where we map in a register page. */
 286         if (((vma->vm_end - vma->vm_start) != PAGE_SIZE) || vma->vm_pgoff)
 287                 return -EINVAL;
 288
 289         /*
 290          * Pick WTCNT as the start, it's usually the first register after the
 291          * FRQCR, and neither one are generally page-aligned out of the box.
 292          */
 293         addr = WTCNT & ~(PAGE_SIZE - 1);
 294
 295         vma->vm_flags |= VM_IO;
 296         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 297
 298         if (io_remap_pfn_range(vma, vma->vm_start, addr >> PAGE_SHIFT,
 299                                PAGE_SIZE, vma->vm_page_prot)) {
 300                 printk(KERN_ERR PFX "%s: io_remap_pfn_range failed\n",
 301                        __FUNCTION__);
 302                 return -EAGAIN;
 303         }
 304
 305         ret = 0;
 306 #endif
 307
 308         return ret;
 309 }
 310
 311 /**
 312  *      sh_wdt_ioctl - Query Device
 313  *      @inode: inode of device
 314  *      @file: file handle of device
 315  *      @cmd: watchdog command
 316  *      @arg: argument
 317  *
 318  *      Query basic information from the device or ping it, as outlined by the
 319  *      watchdog API.
 320  */
 321 static int sh_wdt_ioctl(struct inode *inode, struct file *file,
 322                         unsigned int cmd, unsigned long arg)
 323 {
 324         int new_heartbeat;
 325         int options, retval = -EINVAL;
 326
 327         switch (cmd) {
 328                 case WDIOC_GETSUPPORT:
 329                         return copy_to_user((struct watchdog_info *)arg,
 330                                           &sh_wdt_info,
 331                                           sizeof(sh_wdt_info)) ? -EFAULT : 0;
 332                 case WDIOC_GETSTATUS:
 333                 case WDIOC_GETBOOTSTATUS:
 334                         return put_user(0, (int *)arg);
 335                 case WDIOC_KEEPALIVE:
 336                         sh_wdt_keepalive();
 337                         return 0;
 338                 case WDIOC_SETTIMEOUT:
 339                         if (get_user(new_heartbeat, (int *)arg))
 340                                 return -EFAULT;
 341
 342                         if (sh_wdt_set_heartbeat(new_heartbeat))
 343                                 return -EINVAL;
 344
 345                         sh_wdt_keepalive();
 346                         /* Fall */
 347                 case WDIOC_GETTIMEOUT:
 348                         return put_user(heartbeat, (int *)arg);
 349                 case WDIOC_SETOPTIONS:
 350                         if (get_user(options, (int *)arg))
 351                                 return -EFAULT;
 352
 353                         if (options & WDIOS_DISABLECARD) {
 354                                 sh_wdt_stop();
 355                                 retval = 0;
 356                         }
 357
 358                         if (options & WDIOS_ENABLECARD) {
 359                                 sh_wdt_start();
 360                                 retval = 0;
 361                         }
 362
 363                         return retval;
 364                 default:
 365                         return -ENOTTY;
 366         }
 367
 368         return 0;
 369 }
 370
 371 /**
 372  *      sh_wdt_notify_sys - Notifier Handler
 373  *      @this: notifier block
 374  *      @code: notifier event
 375  *      @unused: unused
 376  *
 377  *      Handles specific events, such as turning off the watchdog during a
 378  *      shutdown event.
 379  */
 380 static int sh_wdt_notify_sys(struct notifier_block *this,
 381                              unsigned long code, void *unused)
 382 {
 383         if (code == SYS_DOWN || code == SYS_HALT)
 384                 sh_wdt_stop();
 385
 386         return NOTIFY_DONE;
 387 }
 388
 389 static const struct file_operations sh_wdt_fops = {
 390         .owner          = THIS_MODULE,
 391         .llseek         = no_llseek,
 392         .write          = sh_wdt_write,
 393         .ioctl          = sh_wdt_ioctl,
 394         .open           = sh_wdt_open,
 395         .release        = sh_wdt_close,
 396         .mmap           = sh_wdt_mmap,
 397 };
 398
 399 static struct watchdog_info sh_wdt_info = {
 400         .options                = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT |
 401                                   WDIOF_MAGICCLOSE,
 402         .firmware_version       = 1,
 403         .identity               = "SH WDT",
 404 };
 405
 406 static struct notifier_block sh_wdt_notifier = {
 407         .notifier_call          = sh_wdt_notify_sys,
 408 };
 409
 410 static struct miscdevice sh_wdt_miscdev = {
 411         .minor          = WATCHDOG_MINOR,
 412         .name           = "watchdog",
 413         .fops           = &sh_wdt_fops,
 414 };
 415
 416 /**
 417  *      sh_wdt_init - Initialize module
 418  *      Registers the device and notifier handler. Actual device
 419  *      initialization is handled by sh_wdt_open().
 420  */
 421 static int __init sh_wdt_init(void)
 422 {
 423         int rc;
 424
 425         if ((clock_division_ratio < 0x5) || (clock_division_ratio > 0x7)) {
 426                 clock_division_ratio = WTCSR_CKS_4096;
 427                 printk(KERN_INFO PFX "clock_division_ratio value must "
 428                        "be 0x5<=x<=0x7, using %d\n", clock_division_ratio);
 429         }
 430
 431         rc = sh_wdt_set_heartbeat(heartbeat);
 432         if (unlikely(rc)) {
 433                 heartbeat = WATCHDOG_HEARTBEAT;
 434                 printk(KERN_INFO PFX "heartbeat value must "
 435                        "be 1<=x<=3600, using %d\n", heartbeat);
 436         }
 437
 438         rc = register_reboot_notifier(&sh_wdt_notifier);
 439         if (unlikely(rc)) {
 440                 printk(KERN_ERR PFX "Can't register reboot notifier (err=%d)\n",
 441                        rc);
 442                 return rc;
 443         }
 444
 445         rc = misc_register(&sh_wdt_miscdev);
 446         if (unlikely(rc)) {
 447                 printk(KERN_ERR PFX "Can't register miscdev on "
 448                        "minor=%d (err=%d)\n", sh_wdt_miscdev.minor, rc);
 449                 unregister_reboot_notifier(&sh_wdt_notifier);
 450                 return rc;
 451         }
 452
 453         printk(KERN_INFO PFX "initialized. heartbeat=%d sec (nowayout=%d)\n",
 454                 heartbeat, nowayout);
 455
 456         return 0;
 457 }
 458
 459 /**
 460  *      sh_wdt_exit - Deinitialize module
 461  *      Unregisters the device and notifier handler. Actual device
 462  *      deinitialization is handled by sh_wdt_close().
 463  */
 464 static void __exit sh_wdt_exit(void)
 465 {
 466         misc_deregister(&sh_wdt_miscdev);
 467         unregister_reboot_notifier(&sh_wdt_notifier);
 468 }
 469
 470 MODULE_AUTHOR("Paul Mundt <lethal@linux-sh.org>");
 471 MODULE_DESCRIPTION("SuperH watchdog driver");
 472 MODULE_LICENSE("GPL");
 473 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 474
 475 module_param(clock_division_ratio, int, 0);
 476 MODULE_PARM_DESC(clock_division_ratio, "Clock division ratio. Valid ranges are from 0x5 (1.31ms) to 0x7 (5.25ms). (default=" __MODULE_STRING(clock_division_ratio) ")");
 477
 478 module_param(heartbeat, int, 0);
 479 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds. (1<=heartbeat<=3600, default=" __MODULE_STRING(WATCHDOG_HEARTBEAT) ")");
 480
 481 module_param(nowayout, int, 0);
 482 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 483
 484 module_init(sh_wdt_init);
 485 module_exit(sh_wdt_exit);