drivers/watchdog/sc520_wdt.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  *  AMD Elan SC520 processor Watchdog Timer driver
0004  *
0005  *  Based on acquirewdt.c by Alan Cox,
0006  *       and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
0007  *
0008  *  The authors do NOT admit liability nor provide warranty for
0009  *  any of this software. This material is provided "AS-IS" in
0010  *  the hope that it may be useful for others.
0011  *
0012  *  (c) Copyright 2001    Scott Jennings <linuxdrivers@oro.net>
0013  *           9/27 - 2001      [Initial release]
0014  *
0015  *  Additional fixes Alan Cox
0016  *  -   Fixed formatting
0017  *  -   Removed debug printks
0018  *  -   Fixed SMP built kernel deadlock
0019  *  -   Switched to private locks not lock_kernel
0020  *  -   Used ioremap/writew/readw
0021  *  -   Added NOWAYOUT support
0022  *  4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>
0023  *  -   Change comments
0024  *  -   Eliminate fop_llseek
0025  *  -   Change CONFIG_WATCHDOG_NOWAYOUT semantics
0026  *  -   Add KERN_* tags to printks
0027  *  -   fix possible wdt_is_open race
0028  *  -   Report proper capabilities in watchdog_info
0029  *  -   Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
0030  *      GETTIMEOUT, SETOPTIONS} ioctls
0031  *  09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>
0032  *  -   cleanup of trailing spaces
0033  *  -   added extra printk's for startup problems
0034  *  -   use module_param
0035  *  -   made timeout (the emulated heartbeat) a module_param
0036  *  -   made the keepalive ping an internal subroutine
0037  *  3/27 - 2004 Changes by Sean Young <sean@mess.org>
0038  *  -   set MMCR_BASE to 0xfffef000
0039  *  -   CBAR does not need to be read
0040  *  -   removed debugging printks
0041  *
0042  *  This WDT driver is different from most other Linux WDT
0043  *  drivers in that the driver will ping the watchdog by itself,
0044  *  because this particular WDT has a very short timeout (1.6
0045  *  seconds) and it would be insane to count on any userspace
0046  *  daemon always getting scheduled within that time frame.
0047  *
0048  *  This driver uses memory mapped IO, and spinlock.
0049  */
0050
0051 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0052
0053 #include <linux/module.h>
0054 #include <linux/moduleparam.h>
0055 #include <linux/types.h>
0056 #include <linux/timer.h>
0057 #include <linux/miscdevice.h>
0058 #include <linux/watchdog.h>
0059 #include <linux/fs.h>
0060 #include <linux/ioport.h>
0061 #include <linux/notifier.h>
0062 #include <linux/reboot.h>
0063 #include <linux/init.h>
0064 #include <linux/jiffies.h>
0065 #include <linux/io.h>
0066 #include <linux/uaccess.h>
0067
0068
0069 /*
0070  * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
0071  *
0072  *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
0073  *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
0074  *
0075  * We will program the SC520 watchdog for a timeout of 2.01s.
0076  * If we reset the watchdog every ~250ms we should be safe.
0077  */
0078
0079 #define WDT_INTERVAL (HZ/4+1)
0080
0081 /*
0082  * We must not require too good response from the userspace daemon.
0083  * Here we require the userspace daemon to send us a heartbeat
0084  * char to /dev/watchdog every 30 seconds.
0085  */
0086
0087 #define WATCHDOG_TIMEOUT 30     /* 30 sec default timeout */
0088 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
0089 static int timeout = WATCHDOG_TIMEOUT;
0090 module_param(timeout, int, 0);
0091 MODULE_PARM_DESC(timeout,
0092     "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
0093                 __MODULE_STRING(WATCHDOG_TIMEOUT) ")");
0094
0095 static bool nowayout = WATCHDOG_NOWAYOUT;
0096 module_param(nowayout, bool, 0);
0097 MODULE_PARM_DESC(nowayout,
0098         "Watchdog cannot be stopped once started (default="
0099                 __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
0100
0101 /*
0102  * AMD Elan SC520 - Watchdog Timer Registers
0103  */
0104 #define MMCR_BASE   0xfffef000  /* The default base address */
0105 #define OFFS_WDTMRCTL   0xCB0   /* Watchdog Timer Control Register */
0106
0107 /* WDT Control Register bit definitions */
0108 #define WDT_EXP_SEL_01  0x0001  /* [01] Time-out = 496 us (with 33 Mhz clk). */
0109 #define WDT_EXP_SEL_02  0x0002  /* [02] Time-out = 508 ms (with 33 Mhz clk). */
0110 #define WDT_EXP_SEL_03  0x0004  /* [03] Time-out = 1.02 s (with 33 Mhz clk). */
0111 #define WDT_EXP_SEL_04  0x0008  /* [04] Time-out = 2.03 s (with 33 Mhz clk). */
0112 #define WDT_EXP_SEL_05  0x0010  /* [05] Time-out = 4.07 s (with 33 Mhz clk). */
0113 #define WDT_EXP_SEL_06  0x0020  /* [06] Time-out = 8.13 s (with 33 Mhz clk). */
0114 #define WDT_EXP_SEL_07  0x0040  /* [07] Time-out = 16.27s (with 33 Mhz clk). */
0115 #define WDT_EXP_SEL_08  0x0080  /* [08] Time-out = 32.54s (with 33 Mhz clk). */
0116 #define WDT_IRQ_FLG 0x1000  /* [12] Interrupt Request Flag */
0117 #define WDT_WRST_ENB    0x4000  /* [14] Watchdog Timer Reset Enable */
0118 #define WDT_ENB     0x8000  /* [15] Watchdog Timer Enable */
0119
0120 static __u16 __iomem *wdtmrctl;
0121
0122 static void wdt_timer_ping(struct timer_list *);
0123 static DEFINE_TIMER(timer, wdt_timer_ping);
0124 static unsigned long next_heartbeat;
0125 static unsigned long wdt_is_open;
0126 static char wdt_expect_close;
0127 static DEFINE_SPINLOCK(wdt_spinlock);
0128
0129 /*
0130  *  Whack the dog
0131  */
0132
0133 static void wdt_timer_ping(struct timer_list *unused)
0134 {
0135     /* If we got a heartbeat pulse within the WDT_US_INTERVAL
0136      * we agree to ping the WDT
0137      */
0138     if (time_before(jiffies, next_heartbeat)) {
0139         /* Ping the WDT */
0140         spin_lock(&wdt_spinlock);
0141         writew(0xAAAA, wdtmrctl);
0142         writew(0x5555, wdtmrctl);
0143         spin_unlock(&wdt_spinlock);
0144
0145         /* Re-set the timer interval */
0146         mod_timer(&timer, jiffies + WDT_INTERVAL);
0147     } else
0148         pr_warn("Heartbeat lost! Will not ping the watchdog\n");
0149 }
0150
0151 /*
0152  *  Utility routines
0153  */
0154
0155 static void wdt_config(int writeval)
0156 {
0157     unsigned long flags;
0158
0159     /* buy some time (ping) */
0160     spin_lock_irqsave(&wdt_spinlock, flags);
0161     readw(wdtmrctl);    /* ensure write synchronization */
0162     writew(0xAAAA, wdtmrctl);
0163     writew(0x5555, wdtmrctl);
0164     /* unlock WDT = make WDT configuration register writable one time */
0165     writew(0x3333, wdtmrctl);
0166     writew(0xCCCC, wdtmrctl);
0167     /* write WDT configuration register */
0168     writew(writeval, wdtmrctl);
0169     spin_unlock_irqrestore(&wdt_spinlock, flags);
0170 }
0171
0172 static int wdt_startup(void)
0173 {
0174     next_heartbeat = jiffies + (timeout * HZ);
0175
0176     /* Start the timer */
0177     mod_timer(&timer, jiffies + WDT_INTERVAL);
0178
0179     /* Start the watchdog */
0180     wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
0181
0182     pr_info("Watchdog timer is now enabled\n");
0183     return 0;
0184 }
0185
0186 static int wdt_turnoff(void)
0187 {
0188     /* Stop the timer */
0189     del_timer_sync(&timer);
0190
0191     /* Stop the watchdog */
0192     wdt_config(0);
0193
0194     pr_info("Watchdog timer is now disabled...\n");
0195     return 0;
0196 }
0197
0198 static int wdt_keepalive(void)
0199 {
0200     /* user land ping */
0201     next_heartbeat = jiffies + (timeout * HZ);
0202     return 0;
0203 }
0204
0205 static int wdt_set_heartbeat(int t)
0206 {
0207     if ((t < 1) || (t > 3600))  /* arbitrary upper limit */
0208         return -EINVAL;
0209
0210     timeout = t;
0211     return 0;
0212 }
0213
0214 /*
0215  *  /dev/watchdog handling
0216  */
0217
0218 static ssize_t fop_write(struct file *file, const char __user *buf,
0219                         size_t count, loff_t *ppos)
0220 {
0221     /* See if we got the magic character 'V' and reload the timer */
0222     if (count) {
0223         if (!nowayout) {
0224             size_t ofs;
0225
0226             /* note: just in case someone wrote the magic character
0227              * five months ago... */
0228             wdt_expect_close = 0;
0229
0230             /* now scan */
0231             for (ofs = 0; ofs != count; ofs++) {
0232                 char c;
0233                 if (get_user(c, buf + ofs))
0234                     return -EFAULT;
0235                 if (c == 'V')
0236                     wdt_expect_close = 42;
0237             }
0238         }
0239
0240         /* Well, anyhow someone wrote to us, we should
0241            return that favour */
0242         wdt_keepalive();
0243     }
0244     return count;
0245 }
0246
0247 static int fop_open(struct inode *inode, struct file *file)
0248 {
0249     /* Just in case we're already talking to someone... */
0250     if (test_and_set_bit(0, &wdt_is_open))
0251         return -EBUSY;
0252     if (nowayout)
0253         __module_get(THIS_MODULE);
0254
0255     /* Good, fire up the show */
0256     wdt_startup();
0257     return stream_open(inode, file);
0258 }
0259
0260 static int fop_close(struct inode *inode, struct file *file)
0261 {
0262     if (wdt_expect_close == 42)
0263         wdt_turnoff();
0264     else {
0265         pr_crit("Unexpected close, not stopping watchdog!\n");
0266         wdt_keepalive();
0267     }
0268     clear_bit(0, &wdt_is_open);
0269     wdt_expect_close = 0;
0270     return 0;
0271 }
0272
0273 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
0274 {
0275     void __user *argp = (void __user *)arg;
0276     int __user *p = argp;
0277     static const struct watchdog_info ident = {
0278         .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
0279                             | WDIOF_MAGICCLOSE,
0280         .firmware_version = 1,
0281         .identity = "SC520",
0282     };
0283
0284     switch (cmd) {
0285     case WDIOC_GETSUPPORT:
0286         return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
0287     case WDIOC_GETSTATUS:
0288     case WDIOC_GETBOOTSTATUS:
0289         return put_user(0, p);
0290     case WDIOC_SETOPTIONS:
0291     {
0292         int new_options, retval = -EINVAL;
0293
0294         if (get_user(new_options, p))
0295             return -EFAULT;
0296
0297         if (new_options & WDIOS_DISABLECARD) {
0298             wdt_turnoff();
0299             retval = 0;
0300         }
0301
0302         if (new_options & WDIOS_ENABLECARD) {
0303             wdt_startup();
0304             retval = 0;
0305         }
0306
0307         return retval;
0308     }
0309     case WDIOC_KEEPALIVE:
0310         wdt_keepalive();
0311         return 0;
0312     case WDIOC_SETTIMEOUT:
0313     {
0314         int new_timeout;
0315
0316         if (get_user(new_timeout, p))
0317             return -EFAULT;
0318
0319         if (wdt_set_heartbeat(new_timeout))
0320             return -EINVAL;
0321
0322         wdt_keepalive();
0323     }
0324         fallthrough;
0325     case WDIOC_GETTIMEOUT:
0326         return put_user(timeout, p);
0327     default:
0328         return -ENOTTY;
0329     }
0330 }
0331
0332 static const struct file_operations wdt_fops = {
0333     .owner      = THIS_MODULE,
0334     .llseek     = no_llseek,
0335     .write      = fop_write,
0336     .open       = fop_open,
0337     .release    = fop_close,
0338     .unlocked_ioctl = fop_ioctl,
0339     .compat_ioctl   = compat_ptr_ioctl,
0340 };
0341
0342 static struct miscdevice wdt_miscdev = {
0343     .minor  = WATCHDOG_MINOR,
0344     .name   = "watchdog",
0345     .fops   = &wdt_fops,
0346 };
0347
0348 /*
0349  *  Notifier for system down
0350  */
0351
0352 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
0353     void *unused)
0354 {
0355     if (code == SYS_DOWN || code == SYS_HALT)
0356         wdt_turnoff();
0357     return NOTIFY_DONE;
0358 }
0359
0360 /*
0361  *  The WDT needs to learn about soft shutdowns in order to
0362  *  turn the timebomb registers off.
0363  */
0364
0365 static struct notifier_block wdt_notifier = {
0366     .notifier_call = wdt_notify_sys,
0367 };
0368
0369 static void __exit sc520_wdt_unload(void)
0370 {
0371     if (!nowayout)
0372         wdt_turnoff();
0373
0374     /* Deregister */
0375     misc_deregister(&wdt_miscdev);
0376     unregister_reboot_notifier(&wdt_notifier);
0377     iounmap(wdtmrctl);
0378 }
0379
0380 static int __init sc520_wdt_init(void)
0381 {
0382     int rc = -EBUSY;
0383
0384     /* Check that the timeout value is within it's range ;
0385        if not reset to the default */
0386     if (wdt_set_heartbeat(timeout)) {
0387         wdt_set_heartbeat(WATCHDOG_TIMEOUT);
0388         pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
0389             WATCHDOG_TIMEOUT);
0390     }
0391
0392     wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
0393     if (!wdtmrctl) {
0394         pr_err("Unable to remap memory\n");
0395         rc = -ENOMEM;
0396         goto err_out_region2;
0397     }
0398
0399     rc = register_reboot_notifier(&wdt_notifier);
0400     if (rc) {
0401         pr_err("cannot register reboot notifier (err=%d)\n", rc);
0402         goto err_out_ioremap;
0403     }
0404
0405     rc = misc_register(&wdt_miscdev);
0406     if (rc) {
0407         pr_err("cannot register miscdev on minor=%d (err=%d)\n",
0408                WATCHDOG_MINOR, rc);
0409         goto err_out_notifier;
0410     }
0411
0412     pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
0413         timeout, nowayout);
0414
0415     return 0;
0416
0417 err_out_notifier:
0418     unregister_reboot_notifier(&wdt_notifier);
0419 err_out_ioremap:
0420     iounmap(wdtmrctl);
0421 err_out_region2:
0422     return rc;
0423 }
0424
0425 module_init(sc520_wdt_init);
0426 module_exit(sc520_wdt_unload);
0427
0428 MODULE_AUTHOR("Scott and Bill Jennings");
0429 MODULE_DESCRIPTION(
0430     "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
0431 MODULE_LICENSE("GPL");