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#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 */
  95static int timeout = WATCHDOG_TIMEOUT;
  96module_param(timeout, int, 0);
  97MODULE_PARM_DESC(timeout,
  98        "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
  99                                __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
 100
 101static int nowayout = WATCHDOG_NOWAYOUT;
 102module_param(nowayout, int, 0);
 103MODULE_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
 126static __u16 __iomem *wdtmrctl;
 127
 128static void wdt_timer_ping(unsigned long);
 129static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
 130static unsigned long next_heartbeat;
 131static unsigned long wdt_is_open;
 132static char wdt_expect_close;
 133static DEFINE_SPINLOCK(wdt_spinlock);
 134
 135/*
 136 *      Whack the dog
 137 */
 138
 139static 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
 162static 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
 180static 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
 194static 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
 206static int wdt_keepalive(void)
 207{
 208        /* user land ping */
 209        next_heartbeat = jiffies + (timeout * HZ);
 210        return 0;
 211}
 212
 213static 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
 226static 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
 255static 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
 268static 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
 282static 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
 341static 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
 350static 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
 360static 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
 373static struct notifier_block wdt_notifier = {
 374        .notifier_call = wdt_notify_sys,
 375};
 376
 377static 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
 388static 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
 429err_out_notifier:
 430        unregister_reboot_notifier(&wdt_notifier);
 431err_out_ioremap:
 432        iounmap(wdtmrctl);
 433err_out_region2:
 434        return rc;
 435}
 436
 437module_init(sc520_wdt_init);
 438module_exit(sc520_wdt_unload);
 439
 440MODULE_AUTHOR("Scott and Bill Jennings");
 441MODULE_DESCRIPTION("Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
 442MODULE_LICENSE("GPL");
 443MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 444