linux/drivers/watchdog/at91sam9_wdt.c
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   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
  60static int heartbeat = WDT_HEARTBEAT;
  61module_param(heartbeat, int, 0);
  62MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  63        "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  64
  65static bool nowayout = WATCHDOG_NOWAYOUT;
  66module_param(nowayout, bool, 0);
  67MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  68        "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  69
  70static void at91_ping(unsigned long data);
  71
  72static 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 */
  86static 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 */
  94static 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 */
 107static 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 */
 121static 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 */
 137static 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
 165static 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 */
 174static 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 */
 212static 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
 242static 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
 251static struct miscdevice at91wdt_miscdev = {
 252        .minor          = WATCHDOG_MINOR,
 253        .name           = "watchdog",
 254        .fops           = &at91wdt_fops,
 255};
 256
 257static 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
 294static 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
 305static struct platform_driver at91wdt_driver = {
 306        .remove         = __exit_p(at91wdt_remove),
 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
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