drivers/watchdog/sc520_wdt.c

   1 /*
   2  *      AMD Elan SC520 processor Watchdog Timer driver
   3  *
   4  *      Based on acquirewdt.c by Alan Cox,
   5  *           and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
   6  *
   7  *      This program is free software; you can redistribute it and/or
   8  *      modify it under the terms of the GNU General Public License
   9  *      as published by the Free Software Foundation; either version
  10  *      2 of the License, or (at your option) any later version.
  11  *
  12  *      The authors do NOT admit liability nor provide warranty for
  13  *      any of this software. This material is provided "AS-IS" in
  14  *      the hope that it may be useful for others.
  15  *
  16  *      (c) Copyright 2001    Scott Jennings <linuxdrivers@oro.net>
  17  *           9/27 - 2001      [Initial release]
  18  *
  19  *      Additional fixes Alan Cox
  20  *      -       Fixed formatting
  21  *      -       Removed debug printks
  22  *      -       Fixed SMP built kernel deadlock
  23  *      -       Switched to private locks not lock_kernel
  24  *      -       Used ioremap/writew/readw
  25  *      -       Added NOWAYOUT support
  26  *      4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>
  27  *      -       Change comments
  28  *      -       Eliminate fop_llseek
  29  *      -       Change CONFIG_WATCHDOG_NOWAYOUT semantics
  30  *      -       Add KERN_* tags to printks
  31  *      -       fix possible wdt_is_open race
  32  *      -       Report proper capabilities in watchdog_info
  33  *      -       Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
  34  *              GETTIMEOUT, SETOPTIONS} ioctls
  35  *      09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>
  36  *      -       cleanup of trailing spaces
  37  *      -       added extra printk's for startup problems
  38  *      -       use module_param
  39  *      -       made timeout (the emulated heartbeat) a module_param
  40  *      -       made the keepalive ping an internal subroutine
  41  *      3/27 - 2004 Changes by Sean Young <sean@mess.org>
  42  *      -       set MMCR_BASE to 0xfffef000
  43  *      -       CBAR does not need to be read
  44  *      -       removed debugging printks
  45  *
  46  *  This WDT driver is different from most other Linux WDT
  47  *  drivers in that the driver will ping the watchdog by itself,
  48  *  because this particular WDT has a very short timeout (1.6
  49  *  seconds) and it would be insane to count on any userspace
  50  *  daemon always getting scheduled within that time frame.
  51  *
  52  *  This driver uses memory mapped IO, and spinlock.
  53  */
  54
  55 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  56
  57 #include <linux/module.h>
  58 #include <linux/moduleparam.h>
  59 #include <linux/types.h>
  60 #include <linux/timer.h>
  61 #include <linux/miscdevice.h>
  62 #include <linux/watchdog.h>
  63 #include <linux/fs.h>
  64 #include <linux/ioport.h>
  65 #include <linux/notifier.h>
  66 #include <linux/reboot.h>
  67 #include <linux/init.h>
  68 #include <linux/jiffies.h>
  69 #include <linux/io.h>
  70 #include <linux/uaccess.h>
  71
  72
  73 /*
  74  * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
  75  *
  76  *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
  77  *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
  78  *
  79  * We will program the SC520 watchdog for a timeout of 2.01s.
  80  * If we reset the watchdog every ~250ms we should be safe.
  81  */
  82
  83 #define WDT_INTERVAL (HZ/4+1)
  84
  85 /*
  86  * We must not require too good response from the userspace daemon.
  87  * Here we require the userspace daemon to send us a heartbeat
  88  * char to /dev/watchdog every 30 seconds.
  89  */
  90
  91 #define WATCHDOG_TIMEOUT 30             /* 30 sec default timeout */
  92 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
  93 static int timeout = WATCHDOG_TIMEOUT;
  94 module_param(timeout, int, 0);
  95 MODULE_PARM_DESC(timeout,
  96         "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
  97                                 __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  98
  99 static bool nowayout = WATCHDOG_NOWAYOUT;
 100 module_param(nowayout, bool, 0);
 101 MODULE_PARM_DESC(nowayout,
 102                 "Watchdog cannot be stopped once started (default="
 103                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 104
 105 /*
 106  * AMD Elan SC520 - Watchdog Timer Registers
 107  */
 108 #define MMCR_BASE       0xfffef000      /* The default base address */
 109 #define OFFS_WDTMRCTL   0xCB0   /* Watchdog Timer Control Register */
 110
 111 /* WDT Control Register bit definitions */
 112 #define WDT_EXP_SEL_01  0x0001  /* [01] Time-out = 496 us (with 33 Mhz clk). */
 113 #define WDT_EXP_SEL_02  0x0002  /* [02] Time-out = 508 ms (with 33 Mhz clk). */
 114 #define WDT_EXP_SEL_03  0x0004  /* [03] Time-out = 1.02 s (with 33 Mhz clk). */
 115 #define WDT_EXP_SEL_04  0x0008  /* [04] Time-out = 2.03 s (with 33 Mhz clk). */
 116 #define WDT_EXP_SEL_05  0x0010  /* [05] Time-out = 4.07 s (with 33 Mhz clk). */
 117 #define WDT_EXP_SEL_06  0x0020  /* [06] Time-out = 8.13 s (with 33 Mhz clk). */
 118 #define WDT_EXP_SEL_07  0x0040  /* [07] Time-out = 16.27s (with 33 Mhz clk). */
 119 #define WDT_EXP_SEL_08  0x0080  /* [08] Time-out = 32.54s (with 33 Mhz clk). */
 120 #define WDT_IRQ_FLG     0x1000  /* [12] Interrupt Request Flag */
 121 #define WDT_WRST_ENB    0x4000  /* [14] Watchdog Timer Reset Enable */
 122 #define WDT_ENB         0x8000  /* [15] Watchdog Timer Enable */
 123
 124 static __u16 __iomem *wdtmrctl;
 125
 126 static void wdt_timer_ping(struct timer_list *);
 127 static DEFINE_TIMER(timer, wdt_timer_ping);
 128 static unsigned long next_heartbeat;
 129 static unsigned long wdt_is_open;
 130 static char wdt_expect_close;
 131 static DEFINE_SPINLOCK(wdt_spinlock);
 132
 133 /*
 134  *      Whack the dog
 135  */
 136
 137 static void wdt_timer_ping(struct timer_list *unused)
 138 {
 139         /* If we got a heartbeat pulse within the WDT_US_INTERVAL
 140          * we agree to ping the WDT
 141          */
 142         if (time_before(jiffies, next_heartbeat)) {
 143                 /* Ping the WDT */
 144                 spin_lock(&wdt_spinlock);
 145                 writew(0xAAAA, wdtmrctl);
 146                 writew(0x5555, wdtmrctl);
 147                 spin_unlock(&wdt_spinlock);
 148
 149                 /* Re-set the timer interval */
 150                 mod_timer(&timer, jiffies + WDT_INTERVAL);
 151         } else
 152                 pr_warn("Heartbeat lost! Will not ping the watchdog\n");
 153 }
 154
 155 /*
 156  *      Utility routines
 157  */
 158
 159 static void wdt_config(int writeval)
 160 {
 161         unsigned long flags;
 162
 163         /* buy some time (ping) */
 164         spin_lock_irqsave(&wdt_spinlock, flags);
 165         readw(wdtmrctl);        /* ensure write synchronization */
 166         writew(0xAAAA, wdtmrctl);
 167         writew(0x5555, wdtmrctl);
 168         /* unlock WDT = make WDT configuration register writable one time */
 169         writew(0x3333, wdtmrctl);
 170         writew(0xCCCC, wdtmrctl);
 171         /* write WDT configuration register */
 172         writew(writeval, wdtmrctl);
 173         spin_unlock_irqrestore(&wdt_spinlock, flags);
 174 }
 175
 176 static int wdt_startup(void)
 177 {
 178         next_heartbeat = jiffies + (timeout * HZ);
 179
 180         /* Start the timer */
 181         mod_timer(&timer, jiffies + WDT_INTERVAL);
 182
 183         /* Start the watchdog */
 184         wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
 185
 186         pr_info("Watchdog timer is now enabled\n");
 187         return 0;
 188 }
 189
 190 static int wdt_turnoff(void)
 191 {
 192         /* Stop the timer */
 193         del_timer(&timer);
 194
 195         /* Stop the watchdog */
 196         wdt_config(0);
 197
 198         pr_info("Watchdog timer is now disabled...\n");
 199         return 0;
 200 }
 201
 202 static int wdt_keepalive(void)
 203 {
 204         /* user land ping */
 205         next_heartbeat = jiffies + (timeout * HZ);
 206         return 0;
 207 }
 208
 209 static int wdt_set_heartbeat(int t)
 210 {
 211         if ((t < 1) || (t > 3600))      /* arbitrary upper limit */
 212                 return -EINVAL;
 213
 214         timeout = t;
 215         return 0;
 216 }
 217
 218 /*
 219  *      /dev/watchdog handling
 220  */
 221
 222 static ssize_t fop_write(struct file *file, const char __user *buf,
 223                                                 size_t count, loff_t *ppos)
 224 {
 225         /* See if we got the magic character 'V' and reload the timer */
 226         if (count) {
 227                 if (!nowayout) {
 228                         size_t ofs;
 229
 230                         /* note: just in case someone wrote the magic character
 231                          * five months ago... */
 232                         wdt_expect_close = 0;
 233
 234                         /* now scan */
 235                         for (ofs = 0; ofs != count; ofs++) {
 236                                 char c;
 237                                 if (get_user(c, buf + ofs))
 238                                         return -EFAULT;
 239                                 if (c == 'V')
 240                                         wdt_expect_close = 42;
 241                         }
 242                 }
 243
 244                 /* Well, anyhow someone wrote to us, we should
 245                    return that favour */
 246                 wdt_keepalive();
 247         }
 248         return count;
 249 }
 250
 251 static int fop_open(struct inode *inode, struct file *file)
 252 {
 253         /* Just in case we're already talking to someone... */
 254         if (test_and_set_bit(0, &wdt_is_open))
 255                 return -EBUSY;
 256         if (nowayout)
 257                 __module_get(THIS_MODULE);
 258
 259         /* Good, fire up the show */
 260         wdt_startup();
 261         return nonseekable_open(inode, file);
 262 }
 263
 264 static int fop_close(struct inode *inode, struct file *file)
 265 {
 266         if (wdt_expect_close == 42)
 267                 wdt_turnoff();
 268         else {
 269                 pr_crit("Unexpected close, not stopping watchdog!\n");
 270                 wdt_keepalive();
 271         }
 272         clear_bit(0, &wdt_is_open);
 273         wdt_expect_close = 0;
 274         return 0;
 275 }
 276
 277 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 278 {
 279         void __user *argp = (void __user *)arg;
 280         int __user *p = argp;
 281         static const struct watchdog_info ident = {
 282                 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
 283                                                         | WDIOF_MAGICCLOSE,
 284                 .firmware_version = 1,
 285                 .identity = "SC520",
 286         };
 287
 288         switch (cmd) {
 289         case WDIOC_GETSUPPORT:
 290                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 291         case WDIOC_GETSTATUS:
 292         case WDIOC_GETBOOTSTATUS:
 293                 return put_user(0, p);
 294         case WDIOC_SETOPTIONS:
 295         {
 296                 int new_options, retval = -EINVAL;
 297
 298                 if (get_user(new_options, p))
 299                         return -EFAULT;
 300
 301                 if (new_options & WDIOS_DISABLECARD) {
 302                         wdt_turnoff();
 303                         retval = 0;
 304                 }
 305
 306                 if (new_options & WDIOS_ENABLECARD) {
 307                         wdt_startup();
 308                         retval = 0;
 309                 }
 310
 311                 return retval;
 312         }
 313         case WDIOC_KEEPALIVE:
 314                 wdt_keepalive();
 315                 return 0;
 316         case WDIOC_SETTIMEOUT:
 317         {
 318                 int new_timeout;
 319
 320                 if (get_user(new_timeout, p))
 321                         return -EFAULT;
 322
 323                 if (wdt_set_heartbeat(new_timeout))
 324                         return -EINVAL;
 325
 326                 wdt_keepalive();
 327                 /* Fall through */
 328         }
 329         case WDIOC_GETTIMEOUT:
 330                 return put_user(timeout, p);
 331         default:
 332                 return -ENOTTY;
 333         }
 334 }
 335
 336 static const struct file_operations wdt_fops = {
 337         .owner          = THIS_MODULE,
 338         .llseek         = no_llseek,
 339         .write          = fop_write,
 340         .open           = fop_open,
 341         .release        = fop_close,
 342         .unlocked_ioctl = fop_ioctl,
 343 };
 344
 345 static struct miscdevice wdt_miscdev = {
 346         .minor  = WATCHDOG_MINOR,
 347         .name   = "watchdog",
 348         .fops   = &wdt_fops,
 349 };
 350
 351 /*
 352  *      Notifier for system down
 353  */
 354
 355 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 356         void *unused)
 357 {
 358         if (code == SYS_DOWN || code == SYS_HALT)
 359                 wdt_turnoff();
 360         return NOTIFY_DONE;
 361 }
 362
 363 /*
 364  *      The WDT needs to learn about soft shutdowns in order to
 365  *      turn the timebomb registers off.
 366  */
 367
 368 static struct notifier_block wdt_notifier = {
 369         .notifier_call = wdt_notify_sys,
 370 };
 371
 372 static void __exit sc520_wdt_unload(void)
 373 {
 374         if (!nowayout)
 375                 wdt_turnoff();
 376
 377         /* Deregister */
 378         misc_deregister(&wdt_miscdev);
 379         unregister_reboot_notifier(&wdt_notifier);
 380         iounmap(wdtmrctl);
 381 }
 382
 383 static int __init sc520_wdt_init(void)
 384 {
 385         int rc = -EBUSY;
 386
 387         /* Check that the timeout value is within it's range ;
 388            if not reset to the default */
 389         if (wdt_set_heartbeat(timeout)) {
 390                 wdt_set_heartbeat(WATCHDOG_TIMEOUT);
 391                 pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
 392                         WATCHDOG_TIMEOUT);
 393         }
 394
 395         wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
 396         if (!wdtmrctl) {
 397                 pr_err("Unable to remap memory\n");
 398                 rc = -ENOMEM;
 399                 goto err_out_region2;
 400         }
 401
 402         rc = register_reboot_notifier(&wdt_notifier);
 403         if (rc) {
 404                 pr_err("cannot register reboot notifier (err=%d)\n", rc);
 405                 goto err_out_ioremap;
 406         }
 407
 408         rc = misc_register(&wdt_miscdev);
 409         if (rc) {
 410                 pr_err("cannot register miscdev on minor=%d (err=%d)\n",
 411                        WATCHDOG_MINOR, rc);
 412                 goto err_out_notifier;
 413         }
 414
 415         pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
 416                 timeout, nowayout);
 417
 418         return 0;
 419
 420 err_out_notifier:
 421         unregister_reboot_notifier(&wdt_notifier);
 422 err_out_ioremap:
 423         iounmap(wdtmrctl);
 424 err_out_region2:
 425         return rc;
 426 }
 427
 428 module_init(sc520_wdt_init);
 429 module_exit(sc520_wdt_unload);
 430
 431 MODULE_AUTHOR("Scott and Bill Jennings");
 432 MODULE_DESCRIPTION(
 433         "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
 434 MODULE_LICENSE("GPL");