drivers/watchdog/sc520_wdt.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      AMD Elan SC520 processor Watchdog Timer driver
   4  *
   5  *      Based on acquirewdt.c by Alan Cox,
   6  *           and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
   7  *
   8  *      The authors do NOT admit liability nor provide warranty for
   9  *      any of this software. This material is provided "AS-IS" in
  10  *      the hope that it may be useful for others.
  11  *
  12  *      (c) Copyright 2001    Scott Jennings <linuxdrivers@oro.net>
  13  *           9/27 - 2001      [Initial release]
  14  *
  15  *      Additional fixes Alan Cox
  16  *      -       Fixed formatting
  17  *      -       Removed debug printks
  18  *      -       Fixed SMP built kernel deadlock
  19  *      -       Switched to private locks not lock_kernel
  20  *      -       Used ioremap/writew/readw
  21  *      -       Added NOWAYOUT support
  22  *      4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>
  23  *      -       Change comments
  24  *      -       Eliminate fop_llseek
  25  *      -       Change CONFIG_WATCHDOG_NOWAYOUT semantics
  26  *      -       Add KERN_* tags to printks
  27  *      -       fix possible wdt_is_open race
  28  *      -       Report proper capabilities in watchdog_info
  29  *      -       Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
  30  *              GETTIMEOUT, SETOPTIONS} ioctls
  31  *      09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>
  32  *      -       cleanup of trailing spaces
  33  *      -       added extra printk's for startup problems
  34  *      -       use module_param
  35  *      -       made timeout (the emulated heartbeat) a module_param
  36  *      -       made the keepalive ping an internal subroutine
  37  *      3/27 - 2004 Changes by Sean Young <sean@mess.org>
  38  *      -       set MMCR_BASE to 0xfffef000
  39  *      -       CBAR does not need to be read
  40  *      -       removed debugging printks
  41  *
  42  *  This WDT driver is different from most other Linux WDT
  43  *  drivers in that the driver will ping the watchdog by itself,
  44  *  because this particular WDT has a very short timeout (1.6
  45  *  seconds) and it would be insane to count on any userspace
  46  *  daemon always getting scheduled within that time frame.
  47  *
  48  *  This driver uses memory mapped IO, and spinlock.
  49  */
  50
  51 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  52
  53 #include <linux/module.h>
  54 #include <linux/moduleparam.h>
  55 #include <linux/types.h>
  56 #include <linux/timer.h>
  57 #include <linux/miscdevice.h>
  58 #include <linux/watchdog.h>
  59 #include <linux/fs.h>
  60 #include <linux/ioport.h>
  61 #include <linux/notifier.h>
  62 #include <linux/reboot.h>
  63 #include <linux/init.h>
  64 #include <linux/jiffies.h>
  65 #include <linux/io.h>
  66 #include <linux/uaccess.h>
  67
  68
  69 /*
  70  * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
  71  *
  72  *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
  73  *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
  74  *
  75  * We will program the SC520 watchdog for a timeout of 2.01s.
  76  * If we reset the watchdog every ~250ms we should be safe.
  77  */
  78
  79 #define WDT_INTERVAL (HZ/4+1)
  80
  81 /*
  82  * We must not require too good response from the userspace daemon.
  83  * Here we require the userspace daemon to send us a heartbeat
  84  * char to /dev/watchdog every 30 seconds.
  85  */
  86
  87 #define WATCHDOG_TIMEOUT 30             /* 30 sec default timeout */
  88 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
  89 static int timeout = WATCHDOG_TIMEOUT;
  90 module_param(timeout, int, 0);
  91 MODULE_PARM_DESC(timeout,
  92         "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
  93                                 __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  94
  95 static bool nowayout = WATCHDOG_NOWAYOUT;
  96 module_param(nowayout, bool, 0);
  97 MODULE_PARM_DESC(nowayout,
  98                 "Watchdog cannot be stopped once started (default="
  99                                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
 100
 101 /*
 102  * AMD Elan SC520 - Watchdog Timer Registers
 103  */
 104 #define MMCR_BASE       0xfffef000      /* The default base address */
 105 #define OFFS_WDTMRCTL   0xCB0   /* Watchdog Timer Control Register */
 106
 107 /* WDT Control Register bit definitions */
 108 #define WDT_EXP_SEL_01  0x0001  /* [01] Time-out = 496 us (with 33 Mhz clk). */
 109 #define WDT_EXP_SEL_02  0x0002  /* [02] Time-out = 508 ms (with 33 Mhz clk). */
 110 #define WDT_EXP_SEL_03  0x0004  /* [03] Time-out = 1.02 s (with 33 Mhz clk). */
 111 #define WDT_EXP_SEL_04  0x0008  /* [04] Time-out = 2.03 s (with 33 Mhz clk). */
 112 #define WDT_EXP_SEL_05  0x0010  /* [05] Time-out = 4.07 s (with 33 Mhz clk). */
 113 #define WDT_EXP_SEL_06  0x0020  /* [06] Time-out = 8.13 s (with 33 Mhz clk). */
 114 #define WDT_EXP_SEL_07  0x0040  /* [07] Time-out = 16.27s (with 33 Mhz clk). */
 115 #define WDT_EXP_SEL_08  0x0080  /* [08] Time-out = 32.54s (with 33 Mhz clk). */
 116 #define WDT_IRQ_FLG     0x1000  /* [12] Interrupt Request Flag */
 117 #define WDT_WRST_ENB    0x4000  /* [14] Watchdog Timer Reset Enable */
 118 #define WDT_ENB         0x8000  /* [15] Watchdog Timer Enable */
 119
 120 static __u16 __iomem *wdtmrctl;
 121
 122 static void wdt_timer_ping(struct timer_list *);
 123 static DEFINE_TIMER(timer, wdt_timer_ping);
 124 static unsigned long next_heartbeat;
 125 static unsigned long wdt_is_open;
 126 static char wdt_expect_close;
 127 static DEFINE_SPINLOCK(wdt_spinlock);
 128
 129 /*
 130  *      Whack the dog
 131  */
 132
 133 static void wdt_timer_ping(struct timer_list *unused)
 134 {
 135         /* If we got a heartbeat pulse within the WDT_US_INTERVAL
 136          * we agree to ping the WDT
 137          */
 138         if (time_before(jiffies, next_heartbeat)) {
 139                 /* Ping the WDT */
 140                 spin_lock(&wdt_spinlock);
 141                 writew(0xAAAA, wdtmrctl);
 142                 writew(0x5555, wdtmrctl);
 143                 spin_unlock(&wdt_spinlock);
 144
 145                 /* Re-set the timer interval */
 146                 mod_timer(&timer, jiffies + WDT_INTERVAL);
 147         } else
 148                 pr_warn("Heartbeat lost! Will not ping the watchdog\n");
 149 }
 150
 151 /*
 152  *      Utility routines
 153  */
 154
 155 static void wdt_config(int writeval)
 156 {
 157         unsigned long flags;
 158
 159         /* buy some time (ping) */
 160         spin_lock_irqsave(&wdt_spinlock, flags);
 161         readw(wdtmrctl);        /* ensure write synchronization */
 162         writew(0xAAAA, wdtmrctl);
 163         writew(0x5555, wdtmrctl);
 164         /* unlock WDT = make WDT configuration register writable one time */
 165         writew(0x3333, wdtmrctl);
 166         writew(0xCCCC, wdtmrctl);
 167         /* write WDT configuration register */
 168         writew(writeval, wdtmrctl);
 169         spin_unlock_irqrestore(&wdt_spinlock, flags);
 170 }
 171
 172 static int wdt_startup(void)
 173 {
 174         next_heartbeat = jiffies + (timeout * HZ);
 175
 176         /* Start the timer */
 177         mod_timer(&timer, jiffies + WDT_INTERVAL);
 178
 179         /* Start the watchdog */
 180         wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
 181
 182         pr_info("Watchdog timer is now enabled\n");
 183         return 0;
 184 }
 185
 186 static int wdt_turnoff(void)
 187 {
 188         /* Stop the timer */
 189         del_timer(&timer);
 190
 191         /* Stop the watchdog */
 192         wdt_config(0);
 193
 194         pr_info("Watchdog timer is now disabled...\n");
 195         return 0;
 196 }
 197
 198 static int wdt_keepalive(void)
 199 {
 200         /* user land ping */
 201         next_heartbeat = jiffies + (timeout * HZ);
 202         return 0;
 203 }
 204
 205 static int wdt_set_heartbeat(int t)
 206 {
 207         if ((t < 1) || (t > 3600))      /* arbitrary upper limit */
 208                 return -EINVAL;
 209
 210         timeout = t;
 211         return 0;
 212 }
 213
 214 /*
 215  *      /dev/watchdog handling
 216  */
 217
 218 static ssize_t fop_write(struct file *file, const char __user *buf,
 219                                                 size_t count, loff_t *ppos)
 220 {
 221         /* See if we got the magic character 'V' and reload the timer */
 222         if (count) {
 223                 if (!nowayout) {
 224                         size_t ofs;
 225
 226                         /* note: just in case someone wrote the magic character
 227                          * five months ago... */
 228                         wdt_expect_close = 0;
 229
 230                         /* now scan */
 231                         for (ofs = 0; ofs != count; ofs++) {
 232                                 char c;
 233                                 if (get_user(c, buf + ofs))
 234                                         return -EFAULT;
 235                                 if (c == 'V')
 236                                         wdt_expect_close = 42;
 237                         }
 238                 }
 239
 240                 /* Well, anyhow someone wrote to us, we should
 241                    return that favour */
 242                 wdt_keepalive();
 243         }
 244         return count;
 245 }
 246
 247 static int fop_open(struct inode *inode, struct file *file)
 248 {
 249         /* Just in case we're already talking to someone... */
 250         if (test_and_set_bit(0, &wdt_is_open))
 251                 return -EBUSY;
 252         if (nowayout)
 253                 __module_get(THIS_MODULE);
 254
 255         /* Good, fire up the show */
 256         wdt_startup();
 257         return stream_open(inode, file);
 258 }
 259
 260 static int fop_close(struct inode *inode, struct file *file)
 261 {
 262         if (wdt_expect_close == 42)
 263                 wdt_turnoff();
 264         else {
 265                 pr_crit("Unexpected close, not stopping watchdog!\n");
 266                 wdt_keepalive();
 267         }
 268         clear_bit(0, &wdt_is_open);
 269         wdt_expect_close = 0;
 270         return 0;
 271 }
 272
 273 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 274 {
 275         void __user *argp = (void __user *)arg;
 276         int __user *p = argp;
 277         static const struct watchdog_info ident = {
 278                 .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
 279                                                         | WDIOF_MAGICCLOSE,
 280                 .firmware_version = 1,
 281                 .identity = "SC520",
 282         };
 283
 284         switch (cmd) {
 285         case WDIOC_GETSUPPORT:
 286                 return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 287         case WDIOC_GETSTATUS:
 288         case WDIOC_GETBOOTSTATUS:
 289                 return put_user(0, p);
 290         case WDIOC_SETOPTIONS:
 291         {
 292                 int new_options, retval = -EINVAL;
 293
 294                 if (get_user(new_options, p))
 295                         return -EFAULT;
 296
 297                 if (new_options & WDIOS_DISABLECARD) {
 298                         wdt_turnoff();
 299                         retval = 0;
 300                 }
 301
 302                 if (new_options & WDIOS_ENABLECARD) {
 303                         wdt_startup();
 304                         retval = 0;
 305                 }
 306
 307                 return retval;
 308         }
 309         case WDIOC_KEEPALIVE:
 310                 wdt_keepalive();
 311                 return 0;
 312         case WDIOC_SETTIMEOUT:
 313         {
 314                 int new_timeout;
 315
 316                 if (get_user(new_timeout, p))
 317                         return -EFAULT;
 318
 319                 if (wdt_set_heartbeat(new_timeout))
 320                         return -EINVAL;
 321
 322                 wdt_keepalive();
 323         }
 324                 fallthrough;
 325         case WDIOC_GETTIMEOUT:
 326                 return put_user(timeout, p);
 327         default:
 328                 return -ENOTTY;
 329         }
 330 }
 331
 332 static const struct file_operations wdt_fops = {
 333         .owner          = THIS_MODULE,
 334         .llseek         = no_llseek,
 335         .write          = fop_write,
 336         .open           = fop_open,
 337         .release        = fop_close,
 338         .unlocked_ioctl = fop_ioctl,
 339         .compat_ioctl   = compat_ptr_ioctl,
 340 };
 341
 342 static struct miscdevice wdt_miscdev = {
 343         .minor  = WATCHDOG_MINOR,
 344         .name   = "watchdog",
 345         .fops   = &wdt_fops,
 346 };
 347
 348 /*
 349  *      Notifier for system down
 350  */
 351
 352 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 353         void *unused)
 354 {
 355         if (code == SYS_DOWN || code == SYS_HALT)
 356                 wdt_turnoff();
 357         return NOTIFY_DONE;
 358 }
 359
 360 /*
 361  *      The WDT needs to learn about soft shutdowns in order to
 362  *      turn the timebomb registers off.
 363  */
 364
 365 static struct notifier_block wdt_notifier = {
 366         .notifier_call = wdt_notify_sys,
 367 };
 368
 369 static void __exit sc520_wdt_unload(void)
 370 {
 371         if (!nowayout)
 372                 wdt_turnoff();
 373
 374         /* Deregister */
 375         misc_deregister(&wdt_miscdev);
 376         unregister_reboot_notifier(&wdt_notifier);
 377         iounmap(wdtmrctl);
 378 }
 379
 380 static int __init sc520_wdt_init(void)
 381 {
 382         int rc = -EBUSY;
 383
 384         /* Check that the timeout value is within it's range ;
 385            if not reset to the default */
 386         if (wdt_set_heartbeat(timeout)) {
 387                 wdt_set_heartbeat(WATCHDOG_TIMEOUT);
 388                 pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
 389                         WATCHDOG_TIMEOUT);
 390         }
 391
 392         wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
 393         if (!wdtmrctl) {
 394                 pr_err("Unable to remap memory\n");
 395                 rc = -ENOMEM;
 396                 goto err_out_region2;
 397         }
 398
 399         rc = register_reboot_notifier(&wdt_notifier);
 400         if (rc) {
 401                 pr_err("cannot register reboot notifier (err=%d)\n", rc);
 402                 goto err_out_ioremap;
 403         }
 404
 405         rc = misc_register(&wdt_miscdev);
 406         if (rc) {
 407                 pr_err("cannot register miscdev on minor=%d (err=%d)\n",
 408                        WATCHDOG_MINOR, rc);
 409                 goto err_out_notifier;
 410         }
 411
 412         pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
 413                 timeout, nowayout);
 414
 415         return 0;
 416
 417 err_out_notifier:
 418         unregister_reboot_notifier(&wdt_notifier);
 419 err_out_ioremap:
 420         iounmap(wdtmrctl);
 421 err_out_region2:
 422         return rc;
 423 }
 424
 425 module_init(sc520_wdt_init);
 426 module_exit(sc520_wdt_unload);
 427
 428 MODULE_AUTHOR("Scott and Bill Jennings");
 429 MODULE_DESCRIPTION(
 430         "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
 431 MODULE_LICENSE("GPL");