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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  19
  20 #include <linux/errno.h>
  21 #include <linux/fs.h>
  22 #include <linux/init.h>
  23 #include <linux/io.h>
  24 #include <linux/kernel.h>
  25 #include <linux/miscdevice.h>
  26 #include <linux/module.h>
  27 #include <linux/moduleparam.h>
  28 #include <linux/platform_device.h>
  29 #include <linux/types.h>
  30 #include <linux/watchdog.h>
  31 #include <linux/jiffies.h>
  32 #include <linux/timer.h>
  33 #include <linux/bitops.h>
  34 #include <linux/uaccess.h>
  35
  36 #include "at91sam9_wdt.h"
  37
  38 #define DRV_NAME "AT91SAM9 Watchdog"
  39
  40 #define wdt_read(field) \
  41         __raw_readl(at91wdt_private.base + field)
  42 #define wdt_write(field, val) \
  43         __raw_writel((val), at91wdt_private.base + field)
  44
  45 /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
  46  * use this to convert a watchdog
  47  * value from/to milliseconds.
  48  */
  49 #define ms_to_ticks(t)  (((t << 8) / 1000) - 1)
  50 #define ticks_to_ms(t)  (((t + 1) * 1000) >> 8)
  51
  52 /* Hardware timeout in seconds */
  53 #define WDT_HW_TIMEOUT 2
  54
  55 /* Timer heartbeat (500ms) */
  56 #define WDT_TIMEOUT     (HZ/2)
  57
  58 /* User land timeout */
  59 #define WDT_HEARTBEAT 15
  60 static int heartbeat = WDT_HEARTBEAT;
  61 module_param(heartbeat, int, 0);
  62 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  63         "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  64
  65 static bool nowayout = WATCHDOG_NOWAYOUT;
  66 module_param(nowayout, bool, 0);
  67 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  68         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  69
  70 static void at91_ping(unsigned long data);
  71
  72 static struct {
  73         void __iomem *base;
  74         unsigned long next_heartbeat;   /* the next_heartbeat for the timer */
  75         unsigned long open;
  76         char expect_close;
  77         struct timer_list timer;        /* The timer that pings the watchdog */
  78 } at91wdt_private;
  79
  80 /* ......................................................................... */
  81
  82
  83 /*
  84  * Reload the watchdog timer.  (ie, pat the watchdog)
  85  */
  86 static inline void at91_wdt_reset(void)
  87 {
  88         wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
  89 }
  90
  91 /*
  92  * Timer tick
  93  */
  94 static void at91_ping(unsigned long data)
  95 {
  96         if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
  97                         (!nowayout && !at91wdt_private.open)) {
  98                 at91_wdt_reset();
  99                 mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 100         } else
 101                 pr_crit("I will reset your machine !\n");
 102 }
 103
 104 /*
 105  * Watchdog device is opened, and watchdog starts running.
 106  */
 107 static int at91_wdt_open(struct inode *inode, struct file *file)
 108 {
 109         if (test_and_set_bit(0, &at91wdt_private.open))
 110                 return -EBUSY;
 111
 112         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 113         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 114
 115         return nonseekable_open(inode, file);
 116 }
 117
 118 /*
 119  * Close the watchdog device.
 120  */
 121 static int at91_wdt_close(struct inode *inode, struct file *file)
 122 {
 123         clear_bit(0, &at91wdt_private.open);
 124
 125         /* stop internal ping */
 126         if (!at91wdt_private.expect_close)
 127                 del_timer(&at91wdt_private.timer);
 128
 129         at91wdt_private.expect_close = 0;
 130         return 0;
 131 }
 132
 133 /*
 134  * Set the watchdog time interval in 1/256Hz (write-once)
 135  * Counter is 12 bit.
 136  */
 137 static int at91_wdt_settimeout(unsigned int timeout)
 138 {
 139         unsigned int reg;
 140         unsigned int mr;
 141
 142         /* Check if disabled */
 143         mr = wdt_read(AT91_WDT_MR);
 144         if (mr & AT91_WDT_WDDIS) {
 145                 pr_err("sorry, watchdog is disabled\n");
 146                 return -EIO;
 147         }
 148
 149         /*
 150          * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
 151          *
 152          * Since WDV is a 12-bit counter, the maximum period is
 153          * 4096 / 256 = 16 seconds.
 154          */
 155         reg = AT91_WDT_WDRSTEN  /* causes watchdog reset */
 156                 /* | AT91_WDT_WDRPROC   causes processor reset only */
 157                 | AT91_WDT_WDDBGHLT     /* disabled in debug mode */
 158                 | AT91_WDT_WDD          /* restart at any time */
 159                 | (timeout & AT91_WDT_WDV);  /* timer value */
 160         wdt_write(AT91_WDT_MR, reg);
 161
 162         return 0;
 163 }
 164
 165 static const struct watchdog_info at91_wdt_info = {
 166         .identity       = DRV_NAME,
 167         .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
 168                                                 WDIOF_MAGICCLOSE,
 169 };
 170
 171 /*
 172  * Handle commands from user-space.
 173  */
 174 static long at91_wdt_ioctl(struct file *file,
 175                 unsigned int cmd, unsigned long arg)
 176 {
 177         void __user *argp = (void __user *)arg;
 178         int __user *p = argp;
 179         int new_value;
 180
 181         switch (cmd) {
 182         case WDIOC_GETSUPPORT:
 183                 return copy_to_user(argp, &at91_wdt_info,
 184                                     sizeof(at91_wdt_info)) ? -EFAULT : 0;
 185
 186         case WDIOC_GETSTATUS:
 187         case WDIOC_GETBOOTSTATUS:
 188                 return put_user(0, p);
 189
 190         case WDIOC_KEEPALIVE:
 191                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 192                 return 0;
 193
 194         case WDIOC_SETTIMEOUT:
 195                 if (get_user(new_value, p))
 196                         return -EFAULT;
 197
 198                 heartbeat = new_value;
 199                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 200
 201                 return put_user(new_value, p);  /* return current value */
 202
 203         case WDIOC_GETTIMEOUT:
 204                 return put_user(heartbeat, p);
 205         }
 206         return -ENOTTY;
 207 }
 208
 209 /*
 210  * Pat the watchdog whenever device is written to.
 211  */
 212 static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
 213                                                                 loff_t *ppos)
 214 {
 215         if (!len)
 216                 return 0;
 217
 218         /* Scan for magic character */
 219         if (!nowayout) {
 220                 size_t i;
 221
 222                 at91wdt_private.expect_close = 0;
 223
 224                 for (i = 0; i < len; i++) {
 225                         char c;
 226                         if (get_user(c, data + i))
 227                                 return -EFAULT;
 228                         if (c == 'V') {
 229                                 at91wdt_private.expect_close = 42;
 230                                 break;
 231                         }
 232                 }
 233         }
 234
 235         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 236
 237         return len;
 238 }
 239
 240 /* ......................................................................... */
 241
 242 static const struct file_operations at91wdt_fops = {
 243         .owner                  = THIS_MODULE,
 244         .llseek                 = no_llseek,
 245         .unlocked_ioctl = at91_wdt_ioctl,
 246         .open                   = at91_wdt_open,
 247         .release                = at91_wdt_close,
 248         .write                  = at91_wdt_write,
 249 };
 250
 251 static struct miscdevice at91wdt_miscdev = {
 252         .minor          = WATCHDOG_MINOR,
 253         .name           = "watchdog",
 254         .fops           = &at91wdt_fops,
 255 };
 256
 257 static int __init at91wdt_probe(struct platform_device *pdev)
 258 {
 259         struct resource *r;
 260         int res;
 261
 262         if (at91wdt_miscdev.parent)
 263                 return -EBUSY;
 264         at91wdt_miscdev.parent = &pdev->dev;
 265
 266         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 267         if (!r)
 268                 return -ENODEV;
 269         at91wdt_private.base = ioremap(r->start, resource_size(r));
 270         if (!at91wdt_private.base) {
 271                 dev_err(&pdev->dev, "failed to map registers, aborting.\n");
 272                 return -ENOMEM;
 273         }
 274
 275         /* Set watchdog */
 276         res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
 277         if (res)
 278                 return res;
 279
 280         res = misc_register(&at91wdt_miscdev);
 281         if (res)
 282                 return res;
 283
 284         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 285         setup_timer(&at91wdt_private.timer, at91_ping, 0);
 286         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 287
 288         pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
 289                 heartbeat, nowayout);
 290
 291         return 0;
 292 }
 293
 294 static int __exit at91wdt_remove(struct platform_device *pdev)
 295 {
 296         int res;
 297
 298         res = misc_deregister(&at91wdt_miscdev);
 299         if (!res)
 300                 at91wdt_miscdev.parent = NULL;
 301
 302         return res;
 303 }
 304
 305 static struct platform_driver at91wdt_driver = {
 306         .remove         = __exit_p(at91wdt_remove),
 307         .driver         = {
 308                 .name   = "at91_wdt",
 309                 .owner  = THIS_MODULE,
 310         },
 311 };
 312
 313 static int __init at91sam_wdt_init(void)
 314 {
 315         return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
 316 }
 317
 318 static void __exit at91sam_wdt_exit(void)
 319 {
 320         platform_driver_unregister(&at91wdt_driver);
 321 }
 322
 323 module_init(at91sam_wdt_init);
 324 module_exit(at91sam_wdt_exit);
 325
 326 MODULE_AUTHOR("Renaud CERRATO <r.cerrato@til-technologies.fr>");
 327 MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
 328 MODULE_LICENSE("GPL");
 329 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);