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 #include <linux/of.h>
  36
  37 #include "at91sam9_wdt.h"
  38
  39 #define DRV_NAME "AT91SAM9 Watchdog"
  40
  41 #define wdt_read(field) \
  42         __raw_readl(at91wdt_private.base + field)
  43 #define wdt_write(field, val) \
  44         __raw_writel((val), at91wdt_private.base + field)
  45
  46 /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
  47  * use this to convert a watchdog
  48  * value from/to milliseconds.
  49  */
  50 #define ms_to_ticks(t)  (((t << 8) / 1000) - 1)
  51 #define ticks_to_ms(t)  (((t + 1) * 1000) >> 8)
  52
  53 /* Hardware timeout in seconds */
  54 #define WDT_HW_TIMEOUT 2
  55
  56 /* Timer heartbeat (500ms) */
  57 #define WDT_TIMEOUT     (HZ/2)
  58
  59 /* User land timeout */
  60 #define WDT_HEARTBEAT 15
  61 static int heartbeat = WDT_HEARTBEAT;
  62 module_param(heartbeat, int, 0);
  63 MODULE_PARM_DESC(heartbeat, "Watchdog heartbeats in seconds. "
  64         "(default = " __MODULE_STRING(WDT_HEARTBEAT) ")");
  65
  66 static bool nowayout = WATCHDOG_NOWAYOUT;
  67 module_param(nowayout, bool, 0);
  68 MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
  69         "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
  70
  71 static void at91_ping(unsigned long data);
  72
  73 static struct {
  74         void __iomem *base;
  75         unsigned long next_heartbeat;   /* the next_heartbeat for the timer */
  76         unsigned long open;
  77         char expect_close;
  78         struct timer_list timer;        /* The timer that pings the watchdog */
  79 } at91wdt_private;
  80
  81 /* ......................................................................... */
  82
  83
  84 /*
  85  * Reload the watchdog timer.  (ie, pat the watchdog)
  86  */
  87 static inline void at91_wdt_reset(void)
  88 {
  89         wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
  90 }
  91
  92 /*
  93  * Timer tick
  94  */
  95 static void at91_ping(unsigned long data)
  96 {
  97         if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
  98                         (!nowayout && !at91wdt_private.open)) {
  99                 at91_wdt_reset();
 100                 mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 101         } else
 102                 pr_crit("I will reset your machine !\n");
 103 }
 104
 105 /*
 106  * Watchdog device is opened, and watchdog starts running.
 107  */
 108 static int at91_wdt_open(struct inode *inode, struct file *file)
 109 {
 110         if (test_and_set_bit(0, &at91wdt_private.open))
 111                 return -EBUSY;
 112
 113         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 114         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 115
 116         return nonseekable_open(inode, file);
 117 }
 118
 119 /*
 120  * Close the watchdog device.
 121  */
 122 static int at91_wdt_close(struct inode *inode, struct file *file)
 123 {
 124         clear_bit(0, &at91wdt_private.open);
 125
 126         /* stop internal ping */
 127         if (!at91wdt_private.expect_close)
 128                 del_timer(&at91wdt_private.timer);
 129
 130         at91wdt_private.expect_close = 0;
 131         return 0;
 132 }
 133
 134 /*
 135  * Set the watchdog time interval in 1/256Hz (write-once)
 136  * Counter is 12 bit.
 137  */
 138 static int at91_wdt_settimeout(unsigned int timeout)
 139 {
 140         unsigned int reg;
 141         unsigned int mr;
 142
 143         /* Check if disabled */
 144         mr = wdt_read(AT91_WDT_MR);
 145         if (mr & AT91_WDT_WDDIS) {
 146                 pr_err("sorry, watchdog is disabled\n");
 147                 return -EIO;
 148         }
 149
 150         /*
 151          * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
 152          *
 153          * Since WDV is a 12-bit counter, the maximum period is
 154          * 4096 / 256 = 16 seconds.
 155          */
 156         reg = AT91_WDT_WDRSTEN  /* causes watchdog reset */
 157                 /* | AT91_WDT_WDRPROC   causes processor reset only */
 158                 | AT91_WDT_WDDBGHLT     /* disabled in debug mode */
 159                 | AT91_WDT_WDD          /* restart at any time */
 160                 | (timeout & AT91_WDT_WDV);  /* timer value */
 161         wdt_write(AT91_WDT_MR, reg);
 162
 163         return 0;
 164 }
 165
 166 static const struct watchdog_info at91_wdt_info = {
 167         .identity       = DRV_NAME,
 168         .options        = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING |
 169                                                 WDIOF_MAGICCLOSE,
 170 };
 171
 172 /*
 173  * Handle commands from user-space.
 174  */
 175 static long at91_wdt_ioctl(struct file *file,
 176                 unsigned int cmd, unsigned long arg)
 177 {
 178         void __user *argp = (void __user *)arg;
 179         int __user *p = argp;
 180         int new_value;
 181
 182         switch (cmd) {
 183         case WDIOC_GETSUPPORT:
 184                 return copy_to_user(argp, &at91_wdt_info,
 185                                     sizeof(at91_wdt_info)) ? -EFAULT : 0;
 186
 187         case WDIOC_GETSTATUS:
 188         case WDIOC_GETBOOTSTATUS:
 189                 return put_user(0, p);
 190
 191         case WDIOC_KEEPALIVE:
 192                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 193                 return 0;
 194
 195         case WDIOC_SETTIMEOUT:
 196                 if (get_user(new_value, p))
 197                         return -EFAULT;
 198
 199                 heartbeat = new_value;
 200                 at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 201
 202                 return put_user(new_value, p);  /* return current value */
 203
 204         case WDIOC_GETTIMEOUT:
 205                 return put_user(heartbeat, p);
 206         }
 207         return -ENOTTY;
 208 }
 209
 210 /*
 211  * Pat the watchdog whenever device is written to.
 212  */
 213 static ssize_t at91_wdt_write(struct file *file, const char *data, size_t len,
 214                                                                 loff_t *ppos)
 215 {
 216         if (!len)
 217                 return 0;
 218
 219         /* Scan for magic character */
 220         if (!nowayout) {
 221                 size_t i;
 222
 223                 at91wdt_private.expect_close = 0;
 224
 225                 for (i = 0; i < len; i++) {
 226                         char c;
 227                         if (get_user(c, data + i))
 228                                 return -EFAULT;
 229                         if (c == 'V') {
 230                                 at91wdt_private.expect_close = 42;
 231                                 break;
 232                         }
 233                 }
 234         }
 235
 236         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 237
 238         return len;
 239 }
 240
 241 /* ......................................................................... */
 242
 243 static const struct file_operations at91wdt_fops = {
 244         .owner                  = THIS_MODULE,
 245         .llseek                 = no_llseek,
 246         .unlocked_ioctl = at91_wdt_ioctl,
 247         .open                   = at91_wdt_open,
 248         .release                = at91_wdt_close,
 249         .write                  = at91_wdt_write,
 250 };
 251
 252 static struct miscdevice at91wdt_miscdev = {
 253         .minor          = WATCHDOG_MINOR,
 254         .name           = "watchdog",
 255         .fops           = &at91wdt_fops,
 256 };
 257
 258 static int __init at91wdt_probe(struct platform_device *pdev)
 259 {
 260         struct resource *r;
 261         int res;
 262
 263         if (at91wdt_miscdev.parent)
 264                 return -EBUSY;
 265         at91wdt_miscdev.parent = &pdev->dev;
 266
 267         r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 268         if (!r)
 269                 return -ENODEV;
 270         at91wdt_private.base = ioremap(r->start, resource_size(r));
 271         if (!at91wdt_private.base) {
 272                 dev_err(&pdev->dev, "failed to map registers, aborting.\n");
 273                 return -ENOMEM;
 274         }
 275
 276         /* Set watchdog */
 277         res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
 278         if (res)
 279                 return res;
 280
 281         res = misc_register(&at91wdt_miscdev);
 282         if (res)
 283                 return res;
 284
 285         at91wdt_private.next_heartbeat = jiffies + heartbeat * HZ;
 286         setup_timer(&at91wdt_private.timer, at91_ping, 0);
 287         mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
 288
 289         pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
 290                 heartbeat, nowayout);
 291
 292         return 0;
 293 }
 294
 295 static int __exit at91wdt_remove(struct platform_device *pdev)
 296 {
 297         int res;
 298
 299         res = misc_deregister(&at91wdt_miscdev);
 300         if (!res)
 301                 at91wdt_miscdev.parent = NULL;
 302
 303         return res;
 304 }
 305
 306 #if defined(CONFIG_OF)
 307 static const struct of_device_id at91_wdt_dt_ids[] __initconst = {
 308         { .compatible = "atmel,at91sam9260-wdt" },
 309         { /* sentinel */ }
 310 };
 311
 312 MODULE_DEVICE_TABLE(of, at91_wdt_dt_ids);
 313 #endif
 314
 315 static struct platform_driver at91wdt_driver = {
 316         .remove         = __exit_p(at91wdt_remove),
 317         .driver         = {
 318                 .name   = "at91_wdt",
 319                 .owner  = THIS_MODULE,
 320                 .of_match_table = of_match_ptr(at91_wdt_dt_ids),
 321         },
 322 };
 323
 324 module_platform_driver_probe(at91wdt_driver, at91wdt_probe);
 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);