linux/drivers/watchdog/sc520_wdt.c
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   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 */
  93static int timeout = WATCHDOG_TIMEOUT;
  94module_param(timeout, int, 0);
  95MODULE_PARM_DESC(timeout,
  96        "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
  97                                __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
  98
  99static bool nowayout = WATCHDOG_NOWAYOUT;
 100module_param(nowayout, bool, 0);
 101MODULE_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
 124static __u16 __iomem *wdtmrctl;
 125
 126static void wdt_timer_ping(unsigned long);
 127static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
 128static unsigned long next_heartbeat;
 129static unsigned long wdt_is_open;
 130static char wdt_expect_close;
 131static DEFINE_SPINLOCK(wdt_spinlock);
 132
 133/*
 134 *      Whack the dog
 135 */
 136
 137static void wdt_timer_ping(unsigned long data)
 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
 159static void wdt_config(int writeval)
 160{
 161        __u16 dummy;
 162        unsigned long flags;
 163
 164        /* buy some time (ping) */
 165        spin_lock_irqsave(&wdt_spinlock, flags);
 166        dummy = readw(wdtmrctl);        /* ensure write synchronization */
 167        writew(0xAAAA, wdtmrctl);
 168        writew(0x5555, wdtmrctl);
 169        /* unlock WDT = make WDT configuration register writable one time */
 170        writew(0x3333, wdtmrctl);
 171        writew(0xCCCC, wdtmrctl);
 172        /* write WDT configuration register */
 173        writew(writeval, wdtmrctl);
 174        spin_unlock_irqrestore(&wdt_spinlock, flags);
 175}
 176
 177static int wdt_startup(void)
 178{
 179        next_heartbeat = jiffies + (timeout * HZ);
 180
 181        /* Start the timer */
 182        mod_timer(&timer, jiffies + WDT_INTERVAL);
 183
 184        /* Start the watchdog */
 185        wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
 186
 187        pr_info("Watchdog timer is now enabled\n");
 188        return 0;
 189}
 190
 191static int wdt_turnoff(void)
 192{
 193        /* Stop the timer */
 194        del_timer(&timer);
 195
 196        /* Stop the watchdog */
 197        wdt_config(0);
 198
 199        pr_info("Watchdog timer is now disabled...\n");
 200        return 0;
 201}
 202
 203static int wdt_keepalive(void)
 204{
 205        /* user land ping */
 206        next_heartbeat = jiffies + (timeout * HZ);
 207        return 0;
 208}
 209
 210static int wdt_set_heartbeat(int t)
 211{
 212        if ((t < 1) || (t > 3600))      /* arbitrary upper limit */
 213                return -EINVAL;
 214
 215        timeout = t;
 216        return 0;
 217}
 218
 219/*
 220 *      /dev/watchdog handling
 221 */
 222
 223static ssize_t fop_write(struct file *file, const char __user *buf,
 224                                                size_t count, loff_t *ppos)
 225{
 226        /* See if we got the magic character 'V' and reload the timer */
 227        if (count) {
 228                if (!nowayout) {
 229                        size_t ofs;
 230
 231                        /* note: just in case someone wrote the magic character
 232                         * five months ago... */
 233                        wdt_expect_close = 0;
 234
 235                        /* now scan */
 236                        for (ofs = 0; ofs != count; ofs++) {
 237                                char c;
 238                                if (get_user(c, buf + ofs))
 239                                        return -EFAULT;
 240                                if (c == 'V')
 241                                        wdt_expect_close = 42;
 242                        }
 243                }
 244
 245                /* Well, anyhow someone wrote to us, we should
 246                   return that favour */
 247                wdt_keepalive();
 248        }
 249        return count;
 250}
 251
 252static int fop_open(struct inode *inode, struct file *file)
 253{
 254        /* Just in case we're already talking to someone... */
 255        if (test_and_set_bit(0, &wdt_is_open))
 256                return -EBUSY;
 257        if (nowayout)
 258                __module_get(THIS_MODULE);
 259
 260        /* Good, fire up the show */
 261        wdt_startup();
 262        return nonseekable_open(inode, file);
 263}
 264
 265static int fop_close(struct inode *inode, struct file *file)
 266{
 267        if (wdt_expect_close == 42)
 268                wdt_turnoff();
 269        else {
 270                pr_crit("Unexpected close, not stopping watchdog!\n");
 271                wdt_keepalive();
 272        }
 273        clear_bit(0, &wdt_is_open);
 274        wdt_expect_close = 0;
 275        return 0;
 276}
 277
 278static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 279{
 280        void __user *argp = (void __user *)arg;
 281        int __user *p = argp;
 282        static const struct watchdog_info ident = {
 283                .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
 284                                                        | WDIOF_MAGICCLOSE,
 285                .firmware_version = 1,
 286                .identity = "SC520",
 287        };
 288
 289        switch (cmd) {
 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_SETOPTIONS:
 296        {
 297                int new_options, retval = -EINVAL;
 298
 299                if (get_user(new_options, p))
 300                        return -EFAULT;
 301
 302                if (new_options & WDIOS_DISABLECARD) {
 303                        wdt_turnoff();
 304                        retval = 0;
 305                }
 306
 307                if (new_options & WDIOS_ENABLECARD) {
 308                        wdt_startup();
 309                        retval = 0;
 310                }
 311
 312                return retval;
 313        }
 314        case WDIOC_KEEPALIVE:
 315                wdt_keepalive();
 316                return 0;
 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        default:
 333                return -ENOTTY;
 334        }
 335}
 336
 337static const struct file_operations wdt_fops = {
 338        .owner          = THIS_MODULE,
 339        .llseek         = no_llseek,
 340        .write          = fop_write,
 341        .open           = fop_open,
 342        .release        = fop_close,
 343        .unlocked_ioctl = fop_ioctl,
 344};
 345
 346static struct miscdevice wdt_miscdev = {
 347        .minor  = WATCHDOG_MINOR,
 348        .name   = "watchdog",
 349        .fops   = &wdt_fops,
 350};
 351
 352/*
 353 *      Notifier for system down
 354 */
 355
 356static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
 357        void *unused)
 358{
 359        if (code == SYS_DOWN || code == SYS_HALT)
 360                wdt_turnoff();
 361        return NOTIFY_DONE;
 362}
 363
 364/*
 365 *      The WDT needs to learn about soft shutdowns in order to
 366 *      turn the timebomb registers off.
 367 */
 368
 369static struct notifier_block wdt_notifier = {
 370        .notifier_call = wdt_notify_sys,
 371};
 372
 373static void __exit sc520_wdt_unload(void)
 374{
 375        if (!nowayout)
 376                wdt_turnoff();
 377
 378        /* Deregister */
 379        misc_deregister(&wdt_miscdev);
 380        unregister_reboot_notifier(&wdt_notifier);
 381        iounmap(wdtmrctl);
 382}
 383
 384static int __init sc520_wdt_init(void)
 385{
 386        int rc = -EBUSY;
 387
 388        /* Check that the timeout value is within it's range ;
 389           if not reset to the default */
 390        if (wdt_set_heartbeat(timeout)) {
 391                wdt_set_heartbeat(WATCHDOG_TIMEOUT);
 392                pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
 393                        WATCHDOG_TIMEOUT);
 394        }
 395
 396        wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
 397        if (!wdtmrctl) {
 398                pr_err("Unable to remap memory\n");
 399                rc = -ENOMEM;
 400                goto err_out_region2;
 401        }
 402
 403        rc = register_reboot_notifier(&wdt_notifier);
 404        if (rc) {
 405                pr_err("cannot register reboot notifier (err=%d)\n", rc);
 406                goto err_out_ioremap;
 407        }
 408
 409        rc = misc_register(&wdt_miscdev);
 410        if (rc) {
 411                pr_err("cannot register miscdev on minor=%d (err=%d)\n",
 412                       WATCHDOG_MINOR, rc);
 413                goto err_out_notifier;
 414        }
 415
 416        pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
 417                timeout, nowayout);
 418
 419        return 0;
 420
 421err_out_notifier:
 422        unregister_reboot_notifier(&wdt_notifier);
 423err_out_ioremap:
 424        iounmap(wdtmrctl);
 425err_out_region2:
 426        return rc;
 427}
 428
 429module_init(sc520_wdt_init);
 430module_exit(sc520_wdt_unload);
 431
 432MODULE_AUTHOR("Scott and Bill Jennings");
 433MODULE_DESCRIPTION(
 434        "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
 435MODULE_LICENSE("GPL");
 436MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 437
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