drivers/watchdog/sbc_epx_c3.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *      SBC EPX C3 0.1  A Hardware Watchdog Device for the Winsystems EPX-C3
   4  *      single board computer
   5  *
   6  *      (c) Copyright 2006 Calin A. Culianu <calin@ajvar.org>, All Rights
   7  *      Reserved.
   8  *
   9  *      based on softdog.c by Alan Cox <alan@lxorguk.ukuu.org.uk>
  10  */
  11
  12 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  13
  14 #include <linux/module.h>
  15 #include <linux/moduleparam.h>
  16 #include <linux/types.h>
  17 #include <linux/kernel.h>
  18 #include <linux/fs.h>
  19 #include <linux/mm.h>
  20 #include <linux/miscdevice.h>
  21 #include <linux/watchdog.h>
  22 #include <linux/notifier.h>
  23 #include <linux/reboot.h>
  24 #include <linux/init.h>
  25 #include <linux/ioport.h>
  26 #include <linux/uaccess.h>
  27 #include <linux/io.h>
  28
  29 static int epx_c3_alive;
  30
  31 #define WATCHDOG_TIMEOUT 1              /* 1 sec default timeout */
  32
  33 static bool nowayout = WATCHDOG_NOWAYOUT;
  34 module_param(nowayout, bool, 0);
  35 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
  36                                         __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  37
  38 #define EPXC3_WATCHDOG_CTL_REG 0x1ee /* write 1 to enable, 0 to disable */
  39 #define EPXC3_WATCHDOG_PET_REG 0x1ef /* write anything to pet once enabled */
  40
  41 static void epx_c3_start(void)
  42 {
  43         outb(1, EPXC3_WATCHDOG_CTL_REG);
  44 }
  45
  46 static void epx_c3_stop(void)
  47 {
  48
  49         outb(0, EPXC3_WATCHDOG_CTL_REG);
  50
  51         pr_info("Stopped watchdog timer\n");
  52 }
  53
  54 static void epx_c3_pet(void)
  55 {
  56         outb(1, EPXC3_WATCHDOG_PET_REG);
  57 }
  58
  59 /*
  60  *      Allow only one person to hold it open
  61  */
  62 static int epx_c3_open(struct inode *inode, struct file *file)
  63 {
  64         if (epx_c3_alive)
  65                 return -EBUSY;
  66
  67         if (nowayout)
  68                 __module_get(THIS_MODULE);
  69
  70         /* Activate timer */
  71         epx_c3_start();
  72         epx_c3_pet();
  73
  74         epx_c3_alive = 1;
  75         pr_info("Started watchdog timer\n");
  76
  77         return stream_open(inode, file);
  78 }
  79
  80 static int epx_c3_release(struct inode *inode, struct file *file)
  81 {
  82         /* Shut off the timer.
  83          * Lock it in if it's a module and we defined ...NOWAYOUT */
  84         if (!nowayout)
  85                 epx_c3_stop();          /* Turn the WDT off */
  86
  87         epx_c3_alive = 0;
  88
  89         return 0;
  90 }
  91
  92 static ssize_t epx_c3_write(struct file *file, const char __user *data,
  93                         size_t len, loff_t *ppos)
  94 {
  95         /* Refresh the timer. */
  96         if (len)
  97                 epx_c3_pet();
  98         return len;
  99 }
 100
 101 static long epx_c3_ioctl(struct file *file, unsigned int cmd,
 102                                                 unsigned long arg)
 103 {
 104         int options, retval = -EINVAL;
 105         int __user *argp = (void __user *)arg;
 106         static const struct watchdog_info ident = {
 107                 .options                = WDIOF_KEEPALIVEPING,
 108                 .firmware_version       = 0,
 109                 .identity               = "Winsystems EPX-C3 H/W Watchdog",
 110         };
 111
 112         switch (cmd) {
 113         case WDIOC_GETSUPPORT:
 114                 if (copy_to_user(argp, &ident, sizeof(ident)))
 115                         return -EFAULT;
 116                 return 0;
 117         case WDIOC_GETSTATUS:
 118         case WDIOC_GETBOOTSTATUS:
 119                 return put_user(0, argp);
 120         case WDIOC_SETOPTIONS:
 121                 if (get_user(options, argp))
 122                         return -EFAULT;
 123
 124                 if (options & WDIOS_DISABLECARD) {
 125                         epx_c3_stop();
 126                         retval = 0;
 127                 }
 128
 129                 if (options & WDIOS_ENABLECARD) {
 130                         epx_c3_start();
 131                         retval = 0;
 132                 }
 133
 134                 return retval;
 135         case WDIOC_KEEPALIVE:
 136                 epx_c3_pet();
 137                 return 0;
 138         case WDIOC_GETTIMEOUT:
 139                 return put_user(WATCHDOG_TIMEOUT, argp);
 140         default:
 141                 return -ENOTTY;
 142         }
 143 }
 144
 145 static int epx_c3_notify_sys(struct notifier_block *this, unsigned long code,
 146                                 void *unused)
 147 {
 148         if (code == SYS_DOWN || code == SYS_HALT)
 149                 epx_c3_stop();          /* Turn the WDT off */
 150
 151         return NOTIFY_DONE;
 152 }
 153
 154 static const struct file_operations epx_c3_fops = {
 155         .owner          = THIS_MODULE,
 156         .llseek         = no_llseek,
 157         .write          = epx_c3_write,
 158         .unlocked_ioctl = epx_c3_ioctl,
 159         .compat_ioctl   = compat_ptr_ioctl,
 160         .open           = epx_c3_open,
 161         .release        = epx_c3_release,
 162 };
 163
 164 static struct miscdevice epx_c3_miscdev = {
 165         .minor          = WATCHDOG_MINOR,
 166         .name           = "watchdog",
 167         .fops           = &epx_c3_fops,
 168 };
 169
 170 static struct notifier_block epx_c3_notifier = {
 171         .notifier_call = epx_c3_notify_sys,
 172 };
 173
 174 static int __init watchdog_init(void)
 175 {
 176         int ret;
 177
 178         if (!request_region(EPXC3_WATCHDOG_CTL_REG, 2, "epxc3_watchdog"))
 179                 return -EBUSY;
 180
 181         ret = register_reboot_notifier(&epx_c3_notifier);
 182         if (ret) {
 183                 pr_err("cannot register reboot notifier (err=%d)\n", ret);
 184                 goto out;
 185         }
 186
 187         ret = misc_register(&epx_c3_miscdev);
 188         if (ret) {
 189                 pr_err("cannot register miscdev on minor=%d (err=%d)\n",
 190                        WATCHDOG_MINOR, ret);
 191                 unregister_reboot_notifier(&epx_c3_notifier);
 192                 goto out;
 193         }
 194
 195         pr_info("Hardware Watchdog Timer for Winsystems EPX-C3 SBC: 0.1\n");
 196
 197         return 0;
 198
 199 out:
 200         release_region(EPXC3_WATCHDOG_CTL_REG, 2);
 201         return ret;
 202 }
 203
 204 static void __exit watchdog_exit(void)
 205 {
 206         misc_deregister(&epx_c3_miscdev);
 207         unregister_reboot_notifier(&epx_c3_notifier);
 208         release_region(EPXC3_WATCHDOG_CTL_REG, 2);
 209 }
 210
 211 module_init(watchdog_init);
 212 module_exit(watchdog_exit);
 213
 214 MODULE_AUTHOR("Calin A. Culianu <calin@ajvar.org>");
 215 MODULE_DESCRIPTION("Hardware Watchdog Device for Winsystems EPX-C3 SBC.  "
 216         "Note that there is no way to probe for this device -- "
 217         "so only use it if you are *sure* you are running on this specific "
 218         "SBC system from Winsystems!  It writes to IO ports 0x1ee and 0x1ef!");
 219 MODULE_LICENSE("GPL");