LXR linux/drivers/watchdog/at91sam9

   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 <mach/at91_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
  53static int heartbeat = WDT_HEARTBEAT;
  54module_param(heartbeat, int, 0);
  55MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  56        "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  57
  58static int nowayout = WATCHDOG_NOWAYOUT;
  59module_param(nowayout, int, 0);
  60MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  61        "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  62
  63static void at91_ping(unsigned long data);
  64
  65static 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 */
  78static 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 */
  86static 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 */
  99static 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 */
 113static 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 */
 129static 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
 157static const struct watchdog_info at91_wdt_info = {
 158        .identity       = DRV_NAME,
 159        .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
 160};
 161
 162/*
 163 * Handle commands from user-space.
 164 */
 165static long at91_wdt_ioctl(struct file *file,
 166                unsigned int cmd, unsigned long arg)
 167{
 168        void __user *argp = (void __user *)arg;
 169        int __user *p = argp;
 170        int new_value;
 171
 172        switch (cmd) {
 173        case WDIOC_GETSUPPORT:
 174                return copy_to_user(argp, &at91_wdt_info,
 175                                    sizeof(at91_wdt_info)) ? -EFAULT : 0;
 176
 177        case WDIOC_GETSTATUS:
 178        case WDIOC_GETBOOTSTATUS:
 179                return put_user(0, p);
 180
 181        case WDIOC_KEEPALIVE:
 182                at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 183                return 0;
 184
 185        case WDIOC_SETTIMEOUT:
 186                if (get_user(new_value, p))
 187                        return -EFAULT;
 188
 189                heartbeat = new_value;
 190                at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 191
 192                return put_user(new_value, p);  /* return current value */
 193
 194        case WDIOC_GETTIMEOUT:
 195                return put_user(heartbeat, p);
 196        }
 197        return -ENOTTY;
 198}
 199
 200/*
 201 * Pat the watchdog whenever device is written to.
 202 */
 203static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
 204                                                                loff_t *ppos)
 205{
 206        if (!len)
 207                return 0;
 208
 209        /* Scan for magic character */
 210        if (!nowayout) {
 211                size_t i;
 212
 213                at91wdt_private.expect_close = 0;
 214
 215                for (i = 0; i < len; i++) {
 216                        char c;
 217                        if (get_user(c, data + i))
 218                                return -EFAULT;
 219                        if (c == 'V') {
 220                                at91wdt_private.expect_close = 42;
 221                                break;
 222                        }
 223                }
 224        }
 225
 226        at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 227
 228        return len;
 229}
 230
 231/* ......................................................................... */
 232
 233static const struct file_operations at91wdt_fops = {
 234        .owner                  = THIS_MODULE,
 235        .llseek                 = no_llseek,
 236        .unlocked_ioctl = at91_wdt_ioctl,
 237        .open                   = at91_wdt_open,
 238        .release                = at91_wdt_close,
 239        .write                  = at91_wdt_write,
 240};
 241
 242static struct miscdevice at91wdt_miscdev = {
 243        .minor          = WATCHDOG_MINOR,
 244        .name           = "watchdog",
 245        .fops           = &at91wdt_fops,
 246};
 247
 248static int __init at91wdt_probe(struct platform_device *pdev)
 249{
 250        int res;
 251
 252        if (at91wdt_miscdev.parent)
 253                return -EBUSY;
 254        at91wdt_miscdev.parent = &pdev->dev;
 255
 256        /* Set watchdog */
 257        res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
 258        if (res)
 259                return res;
 260
 261        res = misc_register(&at91wdt_miscdev);
 262        if (res)
 263                return res;
 264
 265        at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 266        setup_timer(&at91wdt_private.timer, at91_ping, 0);
 267        mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 268
 269        printk(KERN_INFO DRV_NAME " enabled (heartbeat=%d sec, nowayout=%d)\n",
 270                heartbeat, nowayout);
 271
 272        return 0;
 273}
 274
 275static int __exit at91wdt_remove(struct platform_device *pdev)
 276{
 277        int res;
 278
 279        res = misc_deregister(&at91wdt_miscdev);
 280        if (!res)
 281                at91wdt_miscdev.parent = NULL;
 282
 283        return res;
 284}
 285
 286#ifdef CONFIG_PM
 287
 288static int at91wdt_suspend(struct platform_device *pdev, pm_message_t message)
 289{
 290        return 0;
 291}
 292
 293static int at91wdt_resume(struct platform_device *pdev)
 294{
 295        return 0;
 296}
 297
 298#else
 299#define at91wdt_suspend NULL
 300#define at91wdt_resume  NULL
 301#endif
 302
 303static struct platform_driver at91wdt_driver = {
 304        .remove         = __exit_p(at91wdt_remove),
 305        .suspend        = at91wdt_suspend,
 306        .resume         = at91wdt_resume,
 307        .driver         = {
 308                .name   = "at91_wdt",
 309                .owner  = THIS_MODULE,
 310        },
 311};
 312
 313static int __init at91sam_wdt_init(void)
 314{
 315        return platform_driver_probe(&at91wdt_driver, at91wdt_probe);
 316}
 317
 318static void __exit at91sam_wdt_exit(void)
 319{
 320        platform_driver_unregister(&at91wdt_driver);
 321}
 322
 323module_init(at91sam_wdt_init);
 324module_exit(at91sam_wdt_exit);
 325
 326MODULE_AUTHOR("Renaud CERRATO <r.cerrato@til-technologies.fr>");
 327MODULE_DESCRIPTION("Watchdog driver for Atmel AT91SAM9x processors");
 328MODULE_LICENSE("GPL");
 329MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 330