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 #include <linux/module.h>
  56 #include <linux/moduleparam.h>
  57 #include <linux/types.h>
  58 #include <linux/timer.h>
  59 #include <linux/miscdevice.h>
  60 #include <linux/watchdog.h>
  61 #include <linux/fs.h>
  62 #include <linux/ioport.h>
  63 #include <linux/notifier.h>
  64 #include <linux/reboot.h>
  65 #include <linux/init.h>
  66 #include <linux/jiffies.h>
  67 #include <linux/io.h>
  68 #include <linux/uaccess.h>
  69
  70 #include <asm/system.h>
  71
  72 #define OUR_NAME "sc520_wdt"
  73 #define PFX OUR_NAME ": "
  74
  75 /*
  76  * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
  77  *
  78  *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
  79  *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
  80  *
  81  * We will program the SC520 watchdog for a timeout of 2.01s.
  82  * If we reset the watchdog every ~250ms we should be safe.
  83  */
  84
  85 #define WDT_INTERVAL (HZ/4+1)
  86
  87 /*
  88  * We must not require too good response from the userspace daemon.
  89  * Here we require the userspace daemon to send us a heartbeat
  90  * char to /dev/watchdog every 30 seconds.
  91  */
  92
  93 #define WATCHDOG_TIMEOUT 30             /* 30 sec default timeout */
  94 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
  95 static int timeout = WATCHDOG_TIMEOUT;
  96 module_param(timeout, int, 0);
  97 MODULE_PARM_DESC(timeout,
  98         "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
  99                                 __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
 100
 101 static int nowayout = WATCHDOG_NOWAYOUT;
 102 module_param(nowayout, int, 0);
 103 MODULE_PARM_DESC(nowayout,
 104                 "Watchdog cannot be stopped once started (default="
 105                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 106
 107 /*
 108  * AMD Elan SC520 - Watchdog Timer Registers
 109  */
 110 #define MMCR_BASE       0xfffef000      /* The default base address */
 111 #define OFFS_WDTMRCTL   0xCB0   /* Watchdog Timer Control Register */
 112
 113 /* WDT Control Register bit definitions */
 114 #define WDT_EXP_SEL_01  0x0001  /* [01] Time-out = 496 us (with 33 Mhz clk). */
 115 #define WDT_EXP_SEL_02  0x0002  /* [02] Time-out = 508 ms (with 33 Mhz clk). */
 116 #define WDT_EXP_SEL_03  0x0004  /* [03] Time-out = 1.02 s (with 33 Mhz clk). */
 117 #define WDT_EXP_SEL_04  0x0008  /* [04] Time-out = 2.03 s (with 33 Mhz clk). */
 118 #define WDT_EXP_SEL_05  0x0010  /* [05] Time-out = 4.07 s (with 33 Mhz clk). */
 119 #define WDT_EXP_SEL_06  0x0020  /* [06] Time-out = 8.13 s (with 33 Mhz clk). */
 120 #define WDT_EXP_SEL_07  0x0040  /* [07] Time-out = 16.27s (with 33 Mhz clk). */
 121 #define WDT_EXP_SEL_08  0x0080  /* [08] Time-out = 32.54s (with 33 Mhz clk). */
 122 #define WDT_IRQ_FLG     0x1000  /* [12] Interrupt Request Flag */
 123 #define WDT_WRST_ENB    0x4000  /* [14] Watchdog Timer Reset Enable */
 124 #define WDT_ENB         0x8000  /* [15] Watchdog Timer Enable */
 125
 126 static __u16 __iomem *wdtmrctl;
 127
 128 static void wdt_timer_ping(unsigned long);
 129 static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
 130 static unsigned long next_heartbeat;
 131 static unsigned long wdt_is_open;
 132 static char wdt_expect_close;
 133 static DEFINE_SPINLOCK(wdt_spinlock);
 134
 135 /*
 136  *      Whack the dog
 137  */
 138
 139 static void wdt_timer_ping(unsigned long data)
 140 {
 141         /* If we got a heartbeat pulse within the WDT_US_INTERVAL
 142          * we agree to ping the WDT
 143          */
 144         if (time_before(jiffies, next_heartbeat)) {
 145                 /* Ping the WDT */
 146                 spin_lock(&wdt_spinlock);
 147                 writew(0xAAAA, wdtmrctl);
 148                 writew(0x5555, wdtmrctl);
 149                 spin_unlock(&wdt_spinlock);
 150
 151                 /* Re-set the timer interval */
 152                 mod_timer(&timer, jiffies + WDT_INTERVAL);
 153         } else
 154                 printk(KERN_WARNING PFX
 155                         "Heartbeat lost! Will not ping the watchdog\n");
 156 }
 157
 158 /*
 159  *      Utility routines
 160  */
 161
 162 static void wdt_config(int writeval)
 163 {
 164         __u16 dummy;
 165         unsigned long flags;
 166
 167         /* buy some time (ping) */
 168         spin_lock_irqsave(&wdt_spinlock, flags);
 169         dummy = readw(wdtmrctl);        /* ensure write synchronization */
 170         writew(0xAAAA, wdtmrctl);
 171         writew(0x5555, wdtmrctl);
 172         /* unlock WDT = make WDT configuration register writable one time */
 173         writew(0x3333, wdtmrctl);
 174         writew(0xCCCC, wdtmrctl);
 175         /* write WDT configuration register */
 176         writew(writeval, wdtmrctl);
 177         spin_unlock_irqrestore(&wdt_spinlock, flags);
 178 }
 179
 180 static int wdt_startup(void)
 181 {
 182         next_heartbeat = jiffies + (timeout * HZ);
 183
 184         /* Start the timer */
 185         mod_timer(&timer, jiffies + WDT_INTERVAL);
 186
 187         /* Start the watchdog */
 188         wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
 189
 190         printk(KERN_INFO PFX "Watchdog timer is now enabled.\n");
 191         return 0;
 192 }
 193
 194 static int wdt_turnoff(void)
 195 {
 196         /* Stop the timer */
 197         del_timer(&timer);
 198
 199         /* Stop the watchdog */
 200         wdt_config(0);
 201
 202         printk(KERN_INFO PFX "Watchdog timer is now disabled...\n");
 203         return 0;
 204 }
 205
 206 static int wdt_keepalive(void)
 207 {
 208         /* user land ping */
 209         next_heartbeat = jiffies + (timeout * HZ);
 210         return 0;
 211 }
 212
 213 static int wdt_set_heartbeat(int t)
 214 {
 215         if ((t < 1) || (t > 3600))      /* arbitrary upper limit */
 216                 return -EINVAL;
 217
 218         timeout = t;
 219         return 0;
 220 }
 221
 222 /*
 223  *      /dev/watchdog handling
 224  */
 225
 226 static ssize_t fop_write(struct file *file, const char __user *buf,
 227                                                 size_t count, loff_t *ppos)
 228 {
 229         /* See if we got the magic character 'V' and reload the timer */
 230         if (count) {
 231                 if (!nowayout) {
 232                         size_t ofs;
 233
 234                         /* note: just in case someone wrote the magic character
 235                          * five months ago... */
 236                         wdt_expect_close = 0;
 237
 238                         /* now scan */
 239                         for (ofs = 0; ofs != count; ofs++) {
 240                                 char c;
 241                                 if (get_user(c, buf + ofs))
 242                                         return -EFAULT;
 243                                 if (c == 'V')
 244                                         wdt_expect_close = 42;
 245                         }
 246                 }
 247
 248                 /* Well, anyhow someone wrote to us, we should
 249                    return that favour */
 250                 wdt_keepalive();
 251         }
 252         return count;
 253 }
 254
 255 static int fop_open(struct inode *inode, struct file *file)
 256 {
 257         /* Just in case we're already talking to someone... */
 258         if (test_and_set_bit(0, &wdt_is_open))
 259                 return -EBUSY;
 260         if (nowayout)
 261                 __module_get(THIS_MODULE);
 262
 263         /* Good, fire up the show */
 264         wdt_startup();
 265         return nonseekable_open(inode, file);
 266 }
 267
 268 static int fop_close(struct inode *inode, struct file *file)
 269 {
 270         if (wdt_expect_close == 42)
 271                 wdt_turnoff();
 272         else {
 273                 printk(KERN_CRIT PFX
 274                         "Unexpected close, not stopping watchdog!\n");
 275                 wdt_keepalive();
 276         }
 277         clear_bit(0, &wdt_is_open);
 278         wdt_expect_close = 0;
 279         return 0;
 280 }
 281
 282 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 283 {
 284         void __user *argp = (void __user *)arg;
 285         int __user *p = argp;
 286         static const struct watchdog_info ident = {
 287                 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
 288                                                         | WDIOF_MAGICCLOSE,
 289                 .firmware_version = 1,
 290                 .identity = "SC520",
 291         };
 292
 293         switch (cmd) {
 294         case WDIOC_GETSUPPORT:
 295                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 296         case WDIOC_GETSTATUS:
 297         case WDIOC_GETBOOTSTATUS:
 298                 return put_user(0, p);
 299         case WDIOC_SETOPTIONS:
 300         {
 301                 int new_options, retval = -EINVAL;
 302
 303                 if (get_user(new_options, p))
 304                         return -EFAULT;
 305
 306                 if (new_options & WDIOS_DISABLECARD) {
 307                         wdt_turnoff();
 308                         retval = 0;
 309                 }
 310
 311                 if (new_options & WDIOS_ENABLECARD) {
 312                         wdt_startup();
 313                         retval = 0;
 314                 }
 315
 316                 return retval;
 317         }
 318         case WDIOC_KEEPALIVE:
 319                 wdt_keepalive();
 320                 return 0;
 321         case WDIOC_SETTIMEOUT:
 322         {
 323                 int new_timeout;
 324
 325                 if (get_user(new_timeout, p))
 326                         return -EFAULT;
 327
 328                 if (wdt_set_heartbeat(new_timeout))
 329                         return -EINVAL;
 330
 331                 wdt_keepalive();
 332                 /* Fall through */
 333         }
 334         case WDIOC_GETTIMEOUT:
 335                 return put_user(timeout, p);
 336         default:
 337                 return -ENOTTY;
 338         }
 339 }
 340
 341 static const struct file_operations wdt_fops = {
 342         .owner          = THIS_MODULE,
 343         .llseek         = no_llseek,
 344         .write          = fop_write,
 345         .open           = fop_open,
 346         .release        = fop_close,
 347         .unlocked_ioctl = fop_ioctl,
 348 };
 349
 350 static struct miscdevice wdt_miscdev = {
 351         .minor  = WATCHDOG_MINOR,
 352         .name   = "watchdog",
 353         .fops   = &wdt_fops,
 354 };
 355
 356 /*
 357  *      Notifier for system down
 358  */
 359
 360 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 361         void *unused)
 362 {
 363         if (code == SYS_DOWN || code == SYS_HALT)
 364                 wdt_turnoff();
 365         return NOTIFY_DONE;
 366 }
 367
 368 /*
 369  *      The WDT needs to learn about soft shutdowns in order to
 370  *      turn the timebomb registers off.
 371  */
 372
 373 static struct notifier_block wdt_notifier = {
 374         .notifier_call = wdt_notify_sys,
 375 };
 376
 377 static void __exit sc520_wdt_unload(void)
 378 {
 379         if (!nowayout)
 380                 wdt_turnoff();
 381
 382         /* Deregister */
 383         misc_deregister(&wdt_miscdev);
 384         unregister_reboot_notifier(&wdt_notifier);
 385         iounmap(wdtmrctl);
 386 }
 387
 388 static int __init sc520_wdt_init(void)
 389 {
 390         int rc = -EBUSY;
 391
 392         /* Check that the timeout value is within it's range ;
 393            if not reset to the default */
 394         if (wdt_set_heartbeat(timeout)) {
 395                 wdt_set_heartbeat(WATCHDOG_TIMEOUT);
 396                 printk(KERN_INFO PFX
 397                     "timeout value must be 1 <= timeout <= 3600, using %d\n",
 398                                                         WATCHDOG_TIMEOUT);
 399         }
 400
 401         wdtmrctl = ioremap((unsigned long)(MMCR_BASE + OFFS_WDTMRCTL), 2);
 402         if (!wdtmrctl) {
 403                 printk(KERN_ERR PFX "Unable to remap memory\n");
 404                 rc = -ENOMEM;
 405                 goto err_out_region2;
 406         }
 407
 408         rc = register_reboot_notifier(&wdt_notifier);
 409         if (rc) {
 410                 printk(KERN_ERR PFX
 411                         "cannot register reboot notifier (err=%d)\n", rc);
 412                 goto err_out_ioremap;
 413         }
 414
 415         rc = misc_register(&wdt_miscdev);
 416         if (rc) {
 417                 printk(KERN_ERR PFX
 418                         "cannot register miscdev on minor=%d (err=%d)\n",
 419                                                         WATCHDOG_MINOR, rc);
 420                 goto err_out_notifier;
 421         }
 422
 423         printk(KERN_INFO PFX
 424            "WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
 425                                                         timeout, nowayout);
 426
 427         return 0;
 428
 429 err_out_notifier:
 430         unregister_reboot_notifier(&wdt_notifier);
 431 err_out_ioremap:
 432         iounmap(wdtmrctl);
 433 err_out_region2:
 434         return rc;
 435 }
 436
 437 module_init(sc520_wdt_init);
 438 module_exit(sc520_wdt_unload);
 439
 440 MODULE_AUTHOR("Scott and Bill Jennings");
 441 MODULE_DESCRIPTION(
 442         "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
 443 MODULE_LICENSE("GPL");
 444 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);