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/kernel.h>
  22 #include <linux/miscdevice.h>
  23 #include <linux/module.h>
  24 #include <linux/moduleparam.h>
  25 #include <linux/platform_device.h>
  26 #include <linux/types.h>
  27 #include <linux/watchdog.h>
  28 #include <linux/jiffies.h>
  29 #include <linux/timer.h>
  30 #include <linux/bitops.h>
  31 #include <linux/uaccess.h>
  32
  33 #include <mach/at91_wdt.h>
  34
  35 #define DRV_NAME "AT91SAM9 Watchdog"
  36
  37 /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
  38  * use this to convert a watchdog
  39  * value from/to milliseconds.
  40  */
  41 #define ms_to_ticks(t)  (((t << 8) / 1000) - 1)
  42 #define ticks_to_ms(t)  (((t + 1) * 1000) >> 8)
  43
  44 /* Hardware timeout in seconds */
  45 #define WDT_HW_TIMEOUT 2
  46
  47 /* Timer heartbeat (500ms) */
  48 #define WDT_TIMEOUT     (HZ/2)
  49
  50 /* User land timeout */
  51 #define WDT_HEARTBEAT 15
  52 static int heartbeat = WDT_HEARTBEAT;
  53 module_param(heartbeat, int, 0);
  54 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  55         "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  56
  57 static int nowayout = WATCHDOG_NOWAYOUT;
  58 module_param(nowayout, int, 0);
  59 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  60         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  61
  62 static void at91_ping(unsigned long data);
  63
  64 static struct {
  65         unsigned long next_heartbeat;   /* the next_heartbeat for the timer */
  66         unsigned long open;
  67         char expect_close;
  68         struct timer_list timer;        /* The timer that pings the watchdog */
  69 } at91wdt_private;
  70
  71 /* ......................................................................... */
  72
  73
  74 /*
  75  * Reload the watchdog timer.  (ie, pat the watchdog)
  76  */
  77 static inline void at91_wdt_reset(void)
  78 {
  79         at91_sys_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
  80 }
  81
  82 /*
  83  * Timer tick
  84  */
  85 static void at91_ping(unsigned long data)
  86 {
  87         if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
  88                         (!nowayout && !at91wdt_private.open)) {
  89                 at91_wdt_reset();
  90                 mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
  91         } else
  92                 printk(KERN_CRIT DRV_NAME": I will reset your machine !\n");
  93 }
  94
  95 /*
  96  * Watchdog device is opened, and watchdog starts running.
  97  */
  98 static int at91_wdt_open(struct inode *inode, struct file *file)
  99 {
 100         if (test_and_set_bit(0, &at91wdt_private.open))
 101                 return -EBUSY;
 102
 103         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 104         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 105
 106         return nonseekable_open(inode, file);
 107 }
 108
 109 /*
 110  * Close the watchdog device.
 111  */
 112 static int at91_wdt_close(struct inode *inode, struct file *file)
 113 {
 114         clear_bit(0, &at91wdt_private.open);
 115
 116         /* stop internal ping */
 117         if (!at91wdt_private.expect_close)
 118                 del_timer(&at91wdt_private.timer);
 119
 120         at91wdt_private.expect_close = 0;
 121         return 0;
 122 }
 123
 124 /*
 125  * Set the watchdog time interval in 1/256Hz (write-once)
 126  * Counter is 12 bit.
 127  */
 128 static int at91_wdt_settimeout(unsigned int timeout)
 129 {
 130         unsigned int reg;
 131         unsigned int mr;
 132
 133         /* Check if disabled */
 134         mr = at91_sys_read(AT91_WDT_MR);
 135         if (mr & AT91_WDT_WDDIS) {
 136                 printk(KERN_ERR DRV_NAME": sorry, watchdog is disabled\n");
 137                 return -EIO;
 138         }
 139
 140         /*
 141          * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
 142          *
 143          * Since WDV is a 12-bit counter, the maximum period is
 144          * 4096 / 256 = 16 seconds.
 145          */
 146         reg = AT91_WDT_WDRSTEN  /* causes watchdog reset */
 147                 /* | AT91_WDT_WDRPROC   causes processor reset only */
 148                 | AT91_WDT_WDDBGHLT     /* disabled in debug mode */
 149                 | AT91_WDT_WDD          /* restart at any time */
 150                 | (timeout & AT91_WDT_WDV);  /* timer value */
 151         at91_sys_write(AT91_WDT_MR, reg);
 152
 153         return 0;
 154 }
 155
 156 static const struct watchdog_info at91_wdt_info = {
 157         .identity       = DRV_NAME,
 158         .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
 159 };
 160
 161 /*
 162  * Handle commands from user-space.
 163  */
 164 static long at91_wdt_ioctl(struct file *file,
 165                 unsigned int cmd, unsigned long arg)
 166 {
 167         void __user *argp = (void __user *)arg;
 168         int __user *p = argp;
 169         int new_value;
 170
 171         switch (cmd) {
 172         case WDIOC_GETSUPPORT:
 173                 return copy_to_user(argp, &at91_wdt_info,
 174                                     sizeof(at91_wdt_info)) ? -EFAULT : 0;
 175
 176         case WDIOC_GETSTATUS:
 177         case WDIOC_GETBOOTSTATUS:
 178                 return put_user(0, p);
 179
 180         case WDIOC_KEEPALIVE:
 181                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 182                 return 0;
 183
 184         case WDIOC_SETTIMEOUT:
 185                 if (get_user(new_value, p))
 186                         return -EFAULT;
 187
 188                 heartbeat = new_value;
 189                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 190
 191                 return put_user(new_value, p);  /* return current value */
 192
 193         case WDIOC_GETTIMEOUT:
 194                 return put_user(heartbeat, p);
 195         }
 196         return -ENOTTY;
 197 }
 198
 199 /*
 200  * Pat the watchdog whenever device is written to.
 201  */
 202 static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
 203       loff_t *ppos)
 204 {
 205         if (!len)
 206                 return 0;
 207
 208         /* Scan for magic character */
 209         if (!nowayout) {
 210                 size_t i;
 211
 212                 at91wdt_private.expect_close = 0;
 213
 214                 for (i = 0; i < len; i++) {
 215                         char c;
 216                         if (get_user(c, data + i))
 217                                 return -EFAULT;
 218                         if (c == 'V') {
 219                                 at91wdt_private.expect_close = 42;
 220                                 break;
 221                         }
 222                 }
 223         }
 224
 225         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 226
 227         return len;
 228 }
 229
 230 /* ......................................................................... */
 231
 232 static const struct file_operations at91wdt_fops = {
 233         .owner                  = THIS_MODULE,
 234         .llseek                 = no_llseek,
 235         .unlocked_ioctl = at91_wdt_ioctl,
 236         .open                   = at91_wdt_open,
 237         .release                = at91_wdt_close,
 238         .write                  = at91_wdt_write,
 239 };
 240
 241 static struct miscdevice at91wdt_miscdev = {
 242         .minor          = WATCHDOG_MINOR,
 243         .name           = "watchdog",
 244         .fops           = &at91wdt_fops,
 245 };
 246
 247 static int __init at91wdt_probe(struct platform_device *pdev)
 248 {
 249         int res;
 250
 251         if (at91wdt_miscdev.parent)
 252                 return -EBUSY;
 253         at91wdt_miscdev.parent = &pdev->dev;
 254
 255         /* Set watchdog */
 256         res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
 257         if (res)
 258                 return res;
 259
 260         res = misc_register(&at91wdt_miscdev);
 261         if (res)
 262                 return res;
 263
 264         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 265         setup_timer(&at91wdt_private.timer, at91_ping, 0);
 266         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 267
 268         printk(KERN_INFO DRV_NAME " enabled (heartbeat=%d sec, nowayout=%d)\n",
 269                 heartbeat, nowayout);
 270
 271         return 0;
 272 }
 273
 274 static int __exit at91wdt_remove(struct platform_device *pdev)
 275 {
 276         int res;
 277
 278         res = misc_deregister(&at91wdt_miscdev);
 279         if (!res)
 280                 at91wdt_miscdev.parent = NULL;
 281
 282         return res;
 283 }
 284
 285 #ifdef CONFIG_PM
 286
 287 static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
 288 {
 289         return 0;
 290 }
 291
 292 static int at91wdt_resume(struct platform_device *pdev)
 293 {
 294         return 0;
 295 }
 296
 297 #else
 298 #define at91wdt_suspend NULL
 299 #define at91wdt_resume  NULL
 300 #endif
 301
 302 static struct platform_driver at91wdt_driver = {
 303         .remove         = __exit_p(at91wdt_remove),
 304         .suspend        = at91wdt_suspend,
 305         .resume         = at91wdt_resume,
 306         .driver         = {
 307                 .name   = "at91_wdt",
 308                 .owner  = THIS_MODULE,
 309         },
 310 };
 311
 312 static int __init at91sam_wdt_init(void)
 313 {
 314         return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
 315 }
 316
 317 static void __exit at91sam_wdt_exit(void)
 318 {
 319         platform_driver_unregister(&at91wdt_driver);
 320 }
 321
 322 module_init(at91sam_wdt_init);
 323 module_exit(at91sam_wdt_exit);
 324
 325 MODULE_AUTHOR("Renaud CERRATO <r.cerrato@til-technologies.fr>");
 326 MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
 327 MODULE_LICENSE("GPL");
 328 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);