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
  68 #include <asm/io.h>
  69 #include <asm/uaccess.h>
  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 static int timeout = WATCHDOG_TIMEOUT;  /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
  95 module_param(timeout, int, 0);
  96 MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds. (1<=timeout<=3600, default=" __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  97
  98 static int nowayout = WATCHDOG_NOWAYOUT;
  99 module_param(nowayout, int, 0);
 100 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 101
 102 /*
 103  * AMD Elan SC520 - Watchdog Timer Registers
 104  */
 105 #define MMCR_BASE       0xfffef000      /* The default base address */
 106 #define OFFS_WDTMRCTL   0xCB0   /* Watchdog Timer Control Register */
 107
 108 /* WDT Control Register bit definitions */
 109 #define WDT_EXP_SEL_01  0x0001  /* [01] Time-out = 496 us (with 33 Mhz clk). */
 110 #define WDT_EXP_SEL_02  0x0002  /* [02] Time-out = 508 ms (with 33 Mhz clk). */
 111 #define WDT_EXP_SEL_03  0x0004  /* [03] Time-out = 1.02 s (with 33 Mhz clk). */
 112 #define WDT_EXP_SEL_04  0x0008  /* [04] Time-out = 2.03 s (with 33 Mhz clk). */
 113 #define WDT_EXP_SEL_05  0x0010  /* [05] Time-out = 4.07 s (with 33 Mhz clk). */
 114 #define WDT_EXP_SEL_06  0x0020  /* [06] Time-out = 8.13 s (with 33 Mhz clk). */
 115 #define WDT_EXP_SEL_07  0x0040  /* [07] Time-out = 16.27s (with 33 Mhz clk). */
 116 #define WDT_EXP_SEL_08  0x0080  /* [08] Time-out = 32.54s (with 33 Mhz clk). */
 117 #define WDT_IRQ_FLG     0x1000  /* [12] Interrupt Request Flag */
 118 #define WDT_WRST_ENB    0x4000  /* [14] Watchdog Timer Reset Enable */
 119 #define WDT_ENB         0x8000  /* [15] Watchdog Timer Enable */
 120
 121 static __u16 __iomem *wdtmrctl;
 122
 123 static void wdt_timer_ping(unsigned long);
 124 static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
 125 static unsigned long next_heartbeat;
 126 static unsigned long wdt_is_open;
 127 static char wdt_expect_close;
 128 static DEFINE_SPINLOCK(wdt_spinlock);
 129
 130 /*
 131  *      Whack the dog
 132  */
 133
 134 static void wdt_timer_ping(unsigned long data)
 135 {
 136         /* If we got a heartbeat pulse within the WDT_US_INTERVAL
 137          * we agree to ping the WDT
 138          */
 139         if(time_before(jiffies, next_heartbeat))
 140         {
 141                 /* Ping the WDT */
 142                 spin_lock(&wdt_spinlock);
 143                 writew(0xAAAA, wdtmrctl);
 144                 writew(0x5555, wdtmrctl);
 145                 spin_unlock(&wdt_spinlock);
 146
 147                 /* Re-set the timer interval */
 148                 mod_timer(&timer, jiffies + WDT_INTERVAL);
 149         } else {
 150                 printk(KERN_WARNING PFX "Heartbeat lost! Will not ping the watchdog\n");
 151         }
 152 }
 153
 154 /*
 155  *      Utility routines
 156  */
 157
 158 static void wdt_config(int writeval)
 159 {
 160         __u16 dummy;
 161         unsigned long flags;
 162
 163         /* buy some time (ping) */
 164         spin_lock_irqsave(&wdt_spinlock, flags);
 165         dummy=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         printk(KERN_INFO PFX "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         printk(KERN_INFO PFX "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, size_t count, loff_t * ppos)
 223 {
 224         /* See if we got the magic character 'V' and reload the timer */
 225         if(count) {
 226                 if (!nowayout) {
 227                         size_t ofs;
 228
 229                         /* note: just in case someone wrote the magic character
 230                          * five months ago... */
 231                         wdt_expect_close = 0;
 232
 233                         /* now scan */
 234                         for(ofs = 0; ofs != count; ofs++) {
 235                                 char c;
 236                                 if (get_user(c, buf + ofs))
 237                                         return -EFAULT;
 238                                 if(c == 'V')
 239                                         wdt_expect_close = 42;
 240                         }
 241                 }
 242
 243                 /* Well, anyhow someone wrote to us, we should return that favour */
 244                 wdt_keepalive();
 245         }
 246         return count;
 247 }
 248
 249 static int fop_open(struct inode * inode, struct file * file)
 250 {
 251         /* Just in case we're already talking to someone... */
 252         if(test_and_set_bit(0, &wdt_is_open))
 253                 return -EBUSY;
 254         if (nowayout)
 255                 __module_get(THIS_MODULE);
 256
 257         /* Good, fire up the show */
 258         wdt_startup();
 259         return nonseekable_open(inode, file);
 260 }
 261
 262 static int fop_close(struct inode * inode, struct file * file)
 263 {
 264         if(wdt_expect_close == 42) {
 265                 wdt_turnoff();
 266         } else {
 267                 printk(KERN_CRIT PFX "Unexpected close, not stopping watchdog!\n");
 268                 wdt_keepalive();
 269         }
 270         clear_bit(0, &wdt_is_open);
 271         wdt_expect_close = 0;
 272         return 0;
 273 }
 274
 275 static int fop_ioctl(struct inode *inode, struct file *file, unsigned int cmd,
 276         unsigned long arg)
 277 {
 278         void __user *argp = (void __user *)arg;
 279         int __user *p = argp;
 280         static struct watchdog_info ident = {
 281                 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE,
 282                 .firmware_version = 1,
 283                 .identity = "SC520",
 284         };
 285
 286         switch(cmd)
 287         {
 288                 default:
 289                         return -ENOTTY;
 290                 case WDIOC_GETSUPPORT:
 291                         return copy_to_user(argp, &ident, sizeof(ident))?-EFAULT:0;
 292                 case WDIOC_GETSTATUS:
 293                 case WDIOC_GETBOOTSTATUS:
 294                         return put_user(0, p);
 295                 case WDIOC_KEEPALIVE:
 296                         wdt_keepalive();
 297                         return 0;
 298                 case WDIOC_SETOPTIONS:
 299                 {
 300                         int new_options, retval = -EINVAL;
 301
 302                         if(get_user(new_options, p))
 303                                 return -EFAULT;
 304
 305                         if(new_options & WDIOS_DISABLECARD) {
 306                                 wdt_turnoff();
 307                                 retval = 0;
 308                         }
 309
 310                         if(new_options & WDIOS_ENABLECARD) {
 311                                 wdt_startup();
 312                                 retval = 0;
 313                         }
 314
 315                         return retval;
 316                 }
 317                 case WDIOC_SETTIMEOUT:
 318                 {
 319                         int new_timeout;
 320
 321                         if(get_user(new_timeout, p))
 322                                 return -EFAULT;
 323
 324                         if(wdt_set_heartbeat(new_timeout))
 325                                 return -EINVAL;
 326
 327                         wdt_keepalive();
 328                         /* Fall through */
 329                 }
 330                 case WDIOC_GETTIMEOUT:
 331                         return put_user(timeout, p);
 332         }
 333 }
 334
 335 static const struct file_operations wdt_fops = {
 336         .owner          = THIS_MODULE,
 337         .llseek         = no_llseek,
 338         .write          = fop_write,
 339         .open           = fop_open,
 340         .release        = fop_close,
 341         .ioctl          = fop_ioctl,
 342 };
 343
 344 static struct miscdevice wdt_miscdev = {
 345         .minor  = WATCHDOG_MINOR,
 346         .name   = "watchdog",
 347         .fops   = &wdt_fops,
 348 };
 349
 350 /*
 351  *      Notifier for system down
 352  */
 353
 354 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 355         void *unused)
 356 {
 357         if(code==SYS_DOWN || code==SYS_HALT)
 358                 wdt_turnoff();
 359         return NOTIFY_DONE;
 360 }
 361
 362 /*
 363  *      The WDT needs to learn about soft shutdowns in order to
 364  *      turn the timebomb registers off.
 365  */
 366
 367 static struct notifier_block wdt_notifier = {
 368         .notifier_call = wdt_notify_sys,
 369 };
 370
 371 static void __exit sc520_wdt_unload(void)
 372 {
 373         if (!nowayout)
 374                 wdt_turnoff();
 375
 376         /* Deregister */
 377         misc_deregister(&wdt_miscdev);
 378         unregister_reboot_notifier(&wdt_notifier);
 379         iounmap(wdtmrctl);
 380 }
 381
 382 static int __init sc520_wdt_init(void)
 383 {
 384         int rc = -EBUSY;
 385
 386         /* Check that the timeout value is within it's range ; if not reset to the default */
 387         if (wdt_set_heartbeat(timeout)) {
 388                 wdt_set_heartbeat(WATCHDOG_TIMEOUT);
 389                 printk(KERN_INFO PFX "timeout value must be 1<=timeout<=3600, using %d\n",
 390                         WATCHDOG_TIMEOUT);
 391         }
 392
 393         wdtmrctl = ioremap((unsigned long)(MMCR_BASE + OFFS_WDTMRCTL), 2);
 394         if (!wdtmrctl) {
 395                 printk(KERN_ERR PFX "Unable to remap memory\n");
 396                 rc = -ENOMEM;
 397                 goto err_out_region2;
 398         }
 399
 400         rc = register_reboot_notifier(&wdt_notifier);
 401         if (rc) {
 402                 printk(KERN_ERR PFX "cannot register reboot notifier (err=%d)\n",
 403                         rc);
 404                 goto err_out_ioremap;
 405         }
 406
 407         rc = misc_register(&wdt_miscdev);
 408         if (rc) {
 409                 printk(KERN_ERR PFX "cannot register miscdev on minor=%d (err=%d)\n",
 410                         WATCHDOG_MINOR, rc);
 411                 goto err_out_notifier;
 412         }
 413
 414         printk(KERN_INFO PFX "WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
 415                 timeout,nowayout);
 416
 417         return 0;
 418
 419 err_out_notifier:
 420         unregister_reboot_notifier(&wdt_notifier);
 421 err_out_ioremap:
 422         iounmap(wdtmrctl);
 423 err_out_region2:
 424         return rc;
 425 }
 426
 427 module_init(sc520_wdt_init);
 428 module_exit(sc520_wdt_unload);
 429
 430 MODULE_AUTHOR("Scott and Bill Jennings");
 431 MODULE_DESCRIPTION("Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
 432 MODULE_LICENSE("GPL");
 433 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);