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