linux/drivers/watchdog/scx200_wdt.c
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   1/* drivers/char/watchdog/scx200_wdt.c
   2
   3   National Semiconductor SCx200 Watchdog support
   4
   5   Copyright (c) 2001,2002 Christer Weinigel <wingel@nano-system.com>
   6
   7   Some code taken from:
   8   National Semiconductor PC87307/PC97307 (ala SC1200) WDT driver
   9   (c) Copyright 2002 Zwane Mwaikambo <zwane@commfireservices.com>
  10
  11   This program is free software; you can redistribute it and/or
  12   modify it under the terms of the GNU General Public License as
  13   published by the Free Software Foundation; either version 2 of the
  14   License, or (at your option) any later version.
  15
  16   The author(s) of this software shall not be held liable for damages
  17   of any nature resulting due to the use of this software. This
  18   software is provided AS-IS with no warranties. */
  19
  20#include <linux/module.h>
  21#include <linux/moduleparam.h>
  22#include <linux/init.h>
  23#include <linux/miscdevice.h>
  24#include <linux/watchdog.h>
  25#include <linux/notifier.h>
  26#include <linux/reboot.h>
  27#include <linux/fs.h>
  28#include <linux/ioport.h>
  29#include <linux/scx200.h>
  30#include <linux/uaccess.h>
  31#include <linux/io.h>
  32
  33#define NAME "scx200_wdt"
  34
  35MODULE_AUTHOR("Christer Weinigel <wingel@nano-system.com>");
  36MODULE_DESCRIPTION("NatSemi SCx200 Watchdog Driver");
  37MODULE_LICENSE("GPL");
  38MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
  39
  40static int margin = 60;         /* in seconds */
  41module_param(margin, int, 0);
  42MODULE_PARM_DESC(margin, "Watchdog margin in seconds");
  43
  44static int nowayout = WATCHDOG_NOWAYOUT;
  45module_param(nowayout, int, 0);
  46MODULE_PARM_DESC(nowayout, "Disable watchdog shutdown on close");
  47
  48static u16 wdto_restart;
  49static char expect_close;
  50static unsigned long open_lock;
  51static DEFINE_SPINLOCK(scx_lock);
  52
  53/* Bits of the WDCNFG register */
  54#define W_ENABLE 0x00fa         /* Enable watchdog */
  55#define W_DISABLE 0x0000        /* Disable watchdog */
  56
  57/* The scaling factor for the timer, this depends on the value of W_ENABLE */
  58#define W_SCALE (32768/1024)
  59
  60static void scx200_wdt_ping(void)
  61{
  62        spin_lock(&scx_lock);
  63        outw(wdto_restart, scx200_cb_base + SCx200_WDT_WDTO);
  64        spin_unlock(&scx_lock);
  65}
  66
  67static void scx200_wdt_update_margin(void)
  68{
  69        printk(KERN_INFO NAME ": timer margin %d seconds\n", margin);
  70        wdto_restart = margin * W_SCALE;
  71}
  72
  73static void scx200_wdt_enable(void)
  74{
  75        printk(KERN_DEBUG NAME ": enabling watchdog timer, wdto_restart = %d\n",
  76               wdto_restart);
  77
  78        spin_lock(&scx_lock);
  79        outw(0, scx200_cb_base + SCx200_WDT_WDTO);
  80        outb(SCx200_WDT_WDSTS_WDOVF, scx200_cb_base + SCx200_WDT_WDSTS);
  81        outw(W_ENABLE, scx200_cb_base + SCx200_WDT_WDCNFG);
  82        spin_unlock(&scx_lock);
  83
  84        scx200_wdt_ping();
  85}
  86
  87static void scx200_wdt_disable(void)
  88{
  89        printk(KERN_DEBUG NAME ": disabling watchdog timer\n");
  90
  91        spin_lock(&scx_lock);
  92        outw(0, scx200_cb_base + SCx200_WDT_WDTO);
  93        outb(SCx200_WDT_WDSTS_WDOVF, scx200_cb_base + SCx200_WDT_WDSTS);
  94        outw(W_DISABLE, scx200_cb_base + SCx200_WDT_WDCNFG);
  95        spin_unlock(&scx_lock);
  96}
  97
  98static int scx200_wdt_open(struct inode *inode, struct file *file)
  99{
 100        /* only allow one at a time */
 101        if (test_and_set_bit(0, &open_lock))
 102                return -EBUSY;
 103        scx200_wdt_enable();
 104
 105        return nonseekable_open(inode, file);
 106}
 107
 108static int scx200_wdt_release(struct inode *inode, struct file *file)
 109{
 110        if (expect_close != 42)
 111                printk(KERN_WARNING NAME
 112                        ": watchdog device closed unexpectedly, "
 113                        "will not disable the watchdog timer\n");
 114        else if (!nowayout)
 115                scx200_wdt_disable();
 116        expect_close = 0;
 117        clear_bit(0, &open_lock);
 118
 119        return 0;
 120}
 121
 122static int scx200_wdt_notify_sys(struct notifier_block *this,
 123                                      unsigned long code, void *unused)
 124{
 125        if (code == SYS_HALT || code == SYS_POWER_OFF)
 126                if (!nowayout)
 127                        scx200_wdt_disable();
 128
 129        return NOTIFY_DONE;
 130}
 131
 132static struct notifier_block scx200_wdt_notifier = {
 133        .notifier_call = scx200_wdt_notify_sys,
 134};
 135
 136static ssize_t scx200_wdt_write(struct file *file, const char __user *data,
 137                                     size_t len, loff_t *ppos)
 138{
 139        /* check for a magic close character */
 140        if (len) {
 141                size_t i;
 142
 143                scx200_wdt_ping();
 144
 145                expect_close = 0;
 146                for (i = 0; i < len; ++i) {
 147                        char c;
 148                        if (get_user(c, data + i))
 149                                return -EFAULT;
 150                        if (c == 'V')
 151                                expect_close = 42;
 152                }
 153
 154                return len;
 155        }
 156
 157        return 0;
 158}
 159
 160static long scx200_wdt_ioctl(struct file *file, unsigned int cmd,
 161                                                        unsigned long arg)
 162{
 163        void __user *argp = (void __user *)arg;
 164        int __user *p = argp;
 165        static const struct watchdog_info ident = {
 166                .identity = "NatSemi SCx200 Watchdog",
 167                .firmware_version = 1,
 168                .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
 169                                                WDIOF_MAGICCLOSE,
 170        };
 171        int new_margin;
 172
 173        switch (cmd) {
 174        case WDIOC_GETSUPPORT:
 175                if (copy_to_user(argp, &ident, sizeof(ident)))
 176                        return -EFAULT;
 177                return 0;
 178        case WDIOC_GETSTATUS:
 179        case WDIOC_GETBOOTSTATUS:
 180                if (put_user(0, p))
 181                        return -EFAULT;
 182                return 0;
 183        case WDIOC_KEEPALIVE:
 184                scx200_wdt_ping();
 185                return 0;
 186        case WDIOC_SETTIMEOUT:
 187                if (get_user(new_margin, p))
 188                        return -EFAULT;
 189                if (new_margin < 1)
 190                        return -EINVAL;
 191                margin = new_margin;
 192                scx200_wdt_update_margin();
 193                scx200_wdt_ping();
 194        case WDIOC_GETTIMEOUT:
 195                if (put_user(margin, p))
 196                        return -EFAULT;
 197                return 0;
 198        default:
 199                return -ENOTTY;
 200        }
 201}
 202
 203static const struct file_operations scx200_wdt_fops = {
 204        .owner = THIS_MODULE,
 205        .llseek = no_llseek,
 206        .write = scx200_wdt_write,
 207        .unlocked_ioctl = scx200_wdt_ioctl,
 208        .open = scx200_wdt_open,
 209        .release = scx200_wdt_release,
 210};
 211
 212static struct miscdevice scx200_wdt_miscdev = {
 213        .minor = WATCHDOG_MINOR,
 214        .name = "watchdog",
 215        .fops = &scx200_wdt_fops,
 216};
 217
 218static int __init scx200_wdt_init(void)
 219{
 220        int r;
 221
 222        printk(KERN_DEBUG NAME ": NatSemi SCx200 Watchdog Driver\n");
 223
 224        /* check that we have found the configuration block */
 225        if (!scx200_cb_present())
 226                return -ENODEV;
 227
 228        if (!request_region(scx200_cb_base + SCx200_WDT_OFFSET,
 229                            SCx200_WDT_SIZE,
 230                            "NatSemi SCx200 Watchdog")) {
 231                printk(KERN_WARNING NAME ": watchdog I/O region busy\n");
 232                return -EBUSY;
 233        }
 234
 235        scx200_wdt_update_margin();
 236        scx200_wdt_disable();
 237
 238        r = register_reboot_notifier(&scx200_wdt_notifier);
 239        if (r) {
 240                printk(KERN_ERR NAME ": unable to register reboot notifier");
 241                release_region(scx200_cb_base + SCx200_WDT_OFFSET,
 242                                SCx200_WDT_SIZE);
 243                return r;
 244        }
 245
 246        r = misc_register(&scx200_wdt_miscdev);
 247        if (r) {
 248                unregister_reboot_notifier(&scx200_wdt_notifier);
 249                release_region(scx200_cb_base + SCx200_WDT_OFFSET,
 250                                SCx200_WDT_SIZE);
 251                return r;
 252        }
 253
 254        return 0;
 255}
 256
 257static void __exit scx200_wdt_cleanup(void)
 258{
 259        misc_deregister(&scx200_wdt_miscdev);
 260        unregister_reboot_notifier(&scx200_wdt_notifier);
 261        release_region(scx200_cb_base + SCx200_WDT_OFFSET,
 262                       SCx200_WDT_SIZE);
 263}
 264
 265module_init(scx200_wdt_init);
 266module_exit(scx200_wdt_cleanup);
 267
 268/*
 269    Local variables:
 270        compile-command: "make -k -C ../.. SUBDIRS=drivers/char modules"
 271        c-basic-offset: 8
 272    End:
 273*/
 274