drivers/watchdog/at91sam9_wdt.c

   1 /*
   2  * Watchdog driver for Atmel AT91SAM9x processors.
   3  *
   4  * Copyright (C) 2008 Renaud CERRATO r.cerrato@til-technologies.fr
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 /*
  13  * The Watchdog Timer Mode Register can be only written to once. If the
  14  * timeout need to be set from Linux, be sure that the bootstrap or the
  15  * bootloader doesn't write to this register.
  16  */
  17
  18 #include <linux/errno.h>
  19 #include <linux/fs.h>
  20 #include <linux/init.h>
  21 #include <linux/io.h>
  22 #include <linux/kernel.h>
  23 #include <linux/miscdevice.h>
  24 #include <linux/module.h>
  25 #include <linux/moduleparam.h>
  26 #include <linux/platform_device.h>
  27 #include <linux/types.h>
  28 #include <linux/watchdog.h>
  29 #include <linux/jiffies.h>
  30 #include <linux/timer.h>
  31 #include <linux/bitops.h>
  32 #include <linux/uaccess.h>
  33
  34 #include "at91sam9_wdt.h"
  35
  36 #define DRV_NAME "AT91SAM9 Watchdog"
  37
  38 /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
  39  * use this to convert a watchdog
  40  * value from/to milliseconds.
  41  */
  42 #define ms_to_ticks(t)  (((t << 8) / 1000) - 1)
  43 #define ticks_to_ms(t)  (((t + 1) * 1000) >> 8)
  44
  45 /* Hardware timeout in seconds */
  46 #define WDT_HW_TIMEOUT 2
  47
  48 /* Timer heartbeat (500ms) */
  49 #define WDT_TIMEOUT     (HZ/2)
  50
  51 /* User land timeout */
  52 #define WDT_HEARTBEAT 15
  53 static int heartbeat = WDT_HEARTBEAT;
  54 module_param(heartbeat, int, 0);
  55 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  56         "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  57
  58 static int nowayout = WATCHDOG_NOWAYOUT;
  59 module_param(nowayout, int, 0);
  60 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  61         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  62
  63 static void at91_ping(unsigned long data);
  64
  65 static struct {
  66         unsigned long next_heartbeat;   /* the next_heartbeat for the timer */
  67         unsigned long open;
  68         char expect_close;
  69         struct timer_list timer;        /* The timer that pings the watchdog */
  70 } at91wdt_private;
  71
  72 /* ......................................................................... */
  73
  74
  75 /*
  76  * Reload the watchdog timer.  (ie, pat the watchdog)
  77  */
  78 static inline void at91_wdt_reset(void)
  79 {
  80         at91_sys_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
  81 }
  82
  83 /*
  84  * Timer tick
  85  */
  86 static void at91_ping(unsigned long data)
  87 {
  88         if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
  89                         (!nowayout && !at91wdt_private.open)) {
  90                 at91_wdt_reset();
  91                 mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
  92         } else
  93                 printk(KERN_CRIT DRV_NAME": I will reset your machine !\n");
  94 }
  95
  96 /*
  97  * Watchdog device is opened, and watchdog starts running.
  98  */
  99 static int at91_wdt_open(struct inode *inode, struct file *file)
 100 {
 101         if (test_and_set_bit(0, &at91wdt_private.open))
 102                 return -EBUSY;
 103
 104         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 105         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 106
 107         return nonseekable_open(inode, file);
 108 }
 109
 110 /*
 111  * Close the watchdog device.
 112  */
 113 static int at91_wdt_close(struct inode *inode, struct file *file)
 114 {
 115         clear_bit(0, &at91wdt_private.open);
 116
 117         /* stop internal ping */
 118         if (!at91wdt_private.expect_close)
 119                 del_timer(&at91wdt_private.timer);
 120
 121         at91wdt_private.expect_close = 0;
 122         return 0;
 123 }
 124
 125 /*
 126  * Set the watchdog time interval in 1/256Hz (write-once)
 127  * Counter is 12 bit.
 128  */
 129 static int at91_wdt_settimeout(unsigned int timeout)
 130 {
 131         unsigned int reg;
 132         unsigned int mr;
 133
 134         /* Check if disabled */
 135         mr = at91_sys_read(AT91_WDT_MR);
 136         if (mr & AT91_WDT_WDDIS) {
 137                 printk(KERN_ERR DRV_NAME": sorry, watchdog is disabled\n");
 138                 return -EIO;
 139         }
 140
 141         /*
 142          * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
 143          *
 144          * Since WDV is a 12-bit counter, the maximum period is
 145          * 4096 / 256 = 16 seconds.
 146          */
 147         reg = AT91_WDT_WDRSTEN  /* causes watchdog reset */
 148                 /* | AT91_WDT_WDRPROC   causes processor reset only */
 149                 | AT91_WDT_WDDBGHLT     /* disabled in debug mode */
 150                 | AT91_WDT_WDD          /* restart at any time */
 151                 | (timeout & AT91_WDT_WDV);  /* timer value */
 152         at91_sys_write(AT91_WDT_MR, reg);
 153
 154         return 0;
 155 }
 156
 157 static const struct watchdog_info at91_wdt_info = {
 158         .identity       = DRV_NAME,
 159         .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
 160                                                 WDIOF_MAGICCLOSE,
 161 };
 162
 163 /*
 164  * Handle commands from user-space.
 165  */
 166 static long at91_wdt_ioctl(struct file *file,
 167                 unsigned int cmd, unsigned long arg)
 168 {
 169         void __user *argp = (void __user *)arg;
 170         int __user *p = argp;
 171         int new_value;
 172
 173         switch (cmd) {
 174         case WDIOC_GETSUPPORT:
 175                 return copy_to_user(argp, &at91_wdt_info,
 176                                     sizeof(at91_wdt_info)) ? -EFAULT : 0;
 177
 178         case WDIOC_GETSTATUS:
 179         case WDIOC_GETBOOTSTATUS:
 180                 return put_user(0, p);
 181
 182         case WDIOC_KEEPALIVE:
 183                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 184                 return 0;
 185
 186         case WDIOC_SETTIMEOUT:
 187                 if (get_user(new_value, p))
 188                         return -EFAULT;
 189
 190                 heartbeat = new_value;
 191                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 192
 193                 return put_user(new_value, p);  /* return current value */
 194
 195         case WDIOC_GETTIMEOUT:
 196                 return put_user(heartbeat, p);
 197         }
 198         return -ENOTTY;
 199 }
 200
 201 /*
 202  * Pat the watchdog whenever device is written to.
 203  */
 204 static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
 205                                                                 loff_t *ppos)
 206 {
 207         if (!len)
 208                 return 0;
 209
 210         /* Scan for magic character */
 211         if (!nowayout) {
 212                 size_t i;
 213
 214                 at91wdt_private.expect_close = 0;
 215
 216                 for (i = 0; i < len; i++) {
 217                         char c;
 218                         if (get_user(c, data + i))
 219                                 return -EFAULT;
 220                         if (c == 'V') {
 221                                 at91wdt_private.expect_close = 42;
 222                                 break;
 223                         }
 224                 }
 225         }
 226
 227         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 228
 229         return len;
 230 }
 231
 232 /* ......................................................................... */
 233
 234 static const struct file_operations at91wdt_fops = {
 235         .owner                  = THIS_MODULE,
 236         .llseek                 = no_llseek,
 237         .unlocked_ioctl = at91_wdt_ioctl,
 238         .open                   = at91_wdt_open,
 239         .release                = at91_wdt_close,
 240         .write                  = at91_wdt_write,
 241 };
 242
 243 static struct miscdevice at91wdt_miscdev = {
 244         .minor          = WATCHDOG_MINOR,
 245         .name           = "watchdog",
 246         .fops           = &at91wdt_fops,
 247 };
 248
 249 static int __init at91wdt_probe(struct platform_device *pdev)
 250 {
 251         int res;
 252
 253         if (at91wdt_miscdev.parent)
 254                 return -EBUSY;
 255         at91wdt_miscdev.parent = &pdev->dev;
 256
 257         /* Set watchdog */
 258         res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
 259         if (res)
 260                 return res;
 261
 262         res = misc_register(&at91wdt_miscdev);
 263         if (res)
 264                 return res;
 265
 266         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 267         setup_timer(&at91wdt_private.timer, at91_ping, 0);
 268         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 269
 270         printk(KERN_INFO DRV_NAME " enabled (heartbeat=%d sec, nowayout=%d)\n",
 271                 heartbeat, nowayout);
 272
 273         return 0;
 274 }
 275
 276 static int __exit at91wdt_remove(struct platform_device *pdev)
 277 {
 278         int res;
 279
 280         res = misc_deregister(&at91wdt_miscdev);
 281         if (!res)
 282                 at91wdt_miscdev.parent = NULL;
 283
 284         return res;
 285 }
 286
 287 static struct platform_driver at91wdt_driver = {
 288         .remove         = __exit_p(at91wdt_remove),
 289         .driver         = {
 290                 .name   = "at91_wdt",
 291                 .owner  = THIS_MODULE,
 292         },
 293 };
 294
 295 static int __init at91sam_wdt_init(void)
 296 {
 297         return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
 298 }
 299
 300 static void __exit at91sam_wdt_exit(void)
 301 {
 302         platform_driver_unregister(&at91wdt_driver);
 303 }
 304
 305 module_init(at91sam_wdt_init);
 306 module_exit(at91sam_wdt_exit);
 307
 308 MODULE_AUTHOR("Renaud CERRATO <r.cerrato@til-technologies.fr>");
 309 MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
 310 MODULE_LICENSE("GPL");
 311 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);