drivers/watchdog/sb_wdog.c

   1 /*
   2  * Watchdog driver for SiByte SB1 SoCs
   3  *
   4  * Copyright (C) 2007 OnStor, Inc. * Andrew Sharp <andy.sharp@onstor.com>
   5  *
   6  * This driver is intended to make the second of two hardware watchdogs
   7  * on the Sibyte 12XX and 11XX SoCs available to the user.  There are two
   8  * such devices available on the SoC, but it seems that there isn't an
   9  * enumeration class for watchdogs in Linux like there is for RTCs.
  10  * The second is used rather than the first because it uses IRQ 1,
  11  * thereby avoiding all that IRQ 0 problematic nonsense.
  12  *
  13  * I have not tried this driver on a 1480 processor; it might work
  14  * just well enough to really screw things up.
  15  *
  16  * It is a simple timer, and there is an interrupt that is raised the
  17  * first time the timer expires.  The second time it expires, the chip
  18  * is reset and there is no way to redirect that NMI.  Which could
  19  * be problematic in some cases where this chip is sitting on the HT
  20  * bus and has just taken responsibility for providing a cache block.
  21  * Since the reset can't be redirected to the external reset pin, it is
  22  * possible that other HT connected processors might hang and not reset.
  23  * For Linux, a soft reset would probably be even worse than a hard reset.
  24  * There you have it.
  25  *
  26  * The timer takes 23 bits of a 64 bit register (?) as a count value,
  27  * and decrements the count every microsecond, for a max value of
  28  * 0x7fffff usec or about 8.3ish seconds.
  29  *
  30  * This watchdog borrows some user semantics from the softdog driver,
  31  * in that if you close the fd, it leaves the watchdog running, unless
  32  * you previously wrote a 'V' to the fd, in which case it disables
  33  * the watchdog when you close the fd like some other drivers.
  34  *
  35  * Based on various other watchdog drivers, which are probably all
  36  * loosely based on something Alan Cox wrote years ago.
  37  *
  38  *      (c) Copyright 1996 Alan Cox <alan@redhat.com>, All Rights Reserved.
  39  *                              http://www.redhat.com
  40  *
  41  *      This program is free software; you can redistribute it and/or
  42  *      modify it under the terms of the GNU General Public License
  43  *      version 1 or 2 as published by the Free Software Foundation.
  44  *
  45  */
  46 #include <linux/module.h>
  47 #include <linux/io.h>
  48 #include <linux/uaccess.h>
  49 #include <linux/fs.h>
  50 #include <linux/reboot.h>
  51 #include <linux/miscdevice.h>
  52 #include <linux/watchdog.h>
  53 #include <linux/interrupt.h>
  54
  55 #include <asm/sibyte/sb1250.h>
  56 #include <asm/sibyte/sb1250_regs.h>
  57 #include <asm/sibyte/sb1250_int.h>
  58 #include <asm/sibyte/sb1250_scd.h>
  59
  60 static DEFINE_SPINLOCK(sbwd_lock);
  61
  62 /*
  63  * set the initial count value of a timer
  64  *
  65  * wdog is the iomem address of the cfg register
  66  */
  67 void sbwdog_set(char __iomem *wdog, unsigned long t)
  68 {
  69         spin_lock(&sbwd_lock);
  70         __raw_writeb(0, wdog - 0x10);
  71         __raw_writeq(t & 0x7fffffUL, wdog);
  72         spin_unlock(&sbwd_lock);
  73 }
  74
  75 /*
  76  * cause the timer to [re]load it's initial count and start counting
  77  * all over again
  78  *
  79  * wdog is the iomem address of the cfg register
  80  */
  81 void sbwdog_pet(char __iomem *wdog)
  82 {
  83         spin_lock(&sbwd_lock);
  84         __raw_writeb(__raw_readb(wdog) | 1, wdog);
  85         spin_unlock(&sbwd_lock);
  86 }
  87
  88 static unsigned long sbwdog_gate; /* keeps it to one thread only */
  89 static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0));
  90 static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1));
  91 static unsigned long timeout = 0x7fffffUL;      /* useconds: 8.3ish secs. */
  92 static int expect_close;
  93
  94 static const struct watchdog_info ident = {
  95         .options        = WDIOF_CARDRESET | WDIOF_SETTIMEOUT |
  96                                                 WDIOF_KEEPALIVEPING,
  97         .identity       = "SiByte Watchdog",
  98 };
  99
 100 /*
 101  * Allow only a single thread to walk the dog
 102  */
 103 static int sbwdog_open(struct inode *inode, struct file *file)
 104 {
 105         nonseekable_open(inode, file);
 106         if (test_and_set_bit(0, &sbwdog_gate))
 107                 return -EBUSY;
 108         __module_get(THIS_MODULE);
 109
 110         /*
 111          * Activate the timer
 112          */
 113         sbwdog_set(user_dog, timeout);
 114         __raw_writeb(1, user_dog);
 115
 116         return 0;
 117 }
 118
 119 /*
 120  * Put the dog back in the kennel.
 121  */
 122 static int sbwdog_release(struct inode *inode, struct file *file)
 123 {
 124         if (expect_close == 42) {
 125                 __raw_writeb(0, user_dog);
 126                 module_put(THIS_MODULE);
 127         } else {
 128                 printk(KERN_CRIT
 129                         "%s: Unexpected close, not stopping watchdog!\n",
 130                                                 ident.identity);
 131                 sbwdog_pet(user_dog);
 132         }
 133         clear_bit(0, &sbwdog_gate);
 134         expect_close = 0;
 135
 136         return 0;
 137 }
 138
 139 /*
 140  * 42 - the answer
 141  */
 142 static ssize_t sbwdog_write(struct file *file, const char __user *data,
 143                         size_t len, loff_t *ppos)
 144 {
 145         int i;
 146
 147         if (len) {
 148                 /*
 149                  * restart the timer
 150                  */
 151                 expect_close = 0;
 152
 153                 for (i = 0; i != len; i++) {
 154                         char c;
 155
 156                         if (get_user(c, data + i))
 157                                 return -EFAULT;
 158                         if (c == 'V')
 159                                 expect_close = 42;
 160                 }
 161                 sbwdog_pet(user_dog);
 162         }
 163
 164         return len;
 165 }
 166
 167 static long sbwdog_ioctl(struct file *file, unsigned int cmd,
 168                                                 unsigned long arg)
 169 {
 170         int ret = -ENOTTY;
 171         unsigned long time;
 172         void __user *argp = (void __user *)arg;
 173         int __user *p = argp;
 174
 175         switch (cmd) {
 176         case WDIOC_GETSUPPORT:
 177                 ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 178                 break;
 179
 180         case WDIOC_GETSTATUS:
 181         case WDIOC_GETBOOTSTATUS:
 182                 ret = put_user(0, p);
 183                 break;
 184
 185         case WDIOC_KEEPALIVE:
 186                 sbwdog_pet(user_dog);
 187                 ret = 0;
 188                 break;
 189
 190         case WDIOC_SETTIMEOUT:
 191                 ret = get_user(time, p);
 192                 if (ret)
 193                         break;
 194
 195                 time *= 1000000;
 196                 if (time > 0x7fffffUL) {
 197                         ret = -EINVAL;
 198                         break;
 199                 }
 200                 timeout = time;
 201                 sbwdog_set(user_dog, timeout);
 202                 sbwdog_pet(user_dog);
 203
 204         case WDIOC_GETTIMEOUT:
 205                 /*
 206                  * get the remaining count from the ... count register
 207                  * which is 1*8 before the config register
 208                  */
 209                 ret = put_user(__raw_readq(user_dog - 8) / 1000000, p);
 210                 break;
 211         }
 212         return ret;
 213 }
 214
 215 /*
 216  *      Notifier for system down
 217  */
 218 static int sbwdog_notify_sys(struct notifier_block *this, unsigned long code,
 219                                                                 void *erf)
 220 {
 221         if (code == SYS_DOWN || code == SYS_HALT) {
 222                 /*
 223                  * sit and sit
 224                  */
 225                 __raw_writeb(0, user_dog);
 226                 __raw_writeb(0, kern_dog);
 227         }
 228
 229         return NOTIFY_DONE;
 230 }
 231
 232 static const struct file_operations sbwdog_fops = {
 233         .owner          = THIS_MODULE,
 234         .llseek         = no_llseek,
 235         .write          = sbwdog_write,
 236         .unlocked_ioctl = sbwdog_ioctl,
 237         .open           = sbwdog_open,
 238         .release        = sbwdog_release,
 239 };
 240
 241 static struct miscdevice sbwdog_miscdev = {
 242         .minor          = WATCHDOG_MINOR,
 243         .name           = "watchdog",
 244         .fops           = &sbwdog_fops,
 245 };
 246
 247 static struct notifier_block sbwdog_notifier = {
 248         .notifier_call  = sbwdog_notify_sys,
 249 };
 250
 251 /*
 252  * interrupt handler
 253  *
 254  * doesn't do a whole lot for user, but oh so cleverly written so kernel
 255  * code can use it to re-up the watchdog, thereby saving the kernel from
 256  * having to create and maintain a timer, just to tickle another timer,
 257  * which is just so wrong.
 258  */
 259 irqreturn_t sbwdog_interrupt(int irq, void *addr)
 260 {
 261         unsigned long wd_init;
 262         char *wd_cfg_reg = (char *)addr;
 263         u8 cfg;
 264
 265         cfg = __raw_readb(wd_cfg_reg);
 266         wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff;
 267
 268         /*
 269          * if it's the second watchdog timer, it's for those users
 270          */
 271         if (wd_cfg_reg == user_dog)
 272                 printk(KERN_CRIT
 273                         "%s in danger of initiating system reset in %ld.%01ld seconds\n",
 274                         ident.identity, wd_init / 1000000, (wd_init / 100000) % 10);
 275         else
 276                 cfg |= 1;
 277
 278         __raw_writeb(cfg, wd_cfg_reg);
 279
 280         return IRQ_HANDLED;
 281 }
 282
 283 static int __init sbwdog_init(void)
 284 {
 285         int ret;
 286
 287         /*
 288          * register a reboot notifier
 289          */
 290         ret = register_reboot_notifier(&sbwdog_notifier);
 291         if (ret) {
 292                 printk(KERN_ERR
 293                         "%s: cannot register reboot notifier (err=%d)\n",
 294                                                 ident.identity, ret);
 295                 return ret;
 296         }
 297
 298         /*
 299          * get the resources
 300          */
 301
 302         ret = request_irq(1, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED,
 303                 ident.identity, (void *)user_dog);
 304         if (ret) {
 305                 printk(KERN_ERR "%s: failed to request irq 1 - %d\n",
 306                                                 ident.identity, ret);
 307                 return ret;
 308         }
 309
 310         ret = misc_register(&sbwdog_miscdev);
 311         if (ret == 0) {
 312                 printk(KERN_INFO "%s: timeout is %ld.%ld secs\n",
 313                                 ident.identity,
 314                                 timeout / 1000000, (timeout / 100000) % 10);
 315         } else
 316                 free_irq(1, (void *)user_dog);
 317         return ret;
 318 }
 319
 320 static void __exit sbwdog_exit(void)
 321 {
 322         misc_deregister(&sbwdog_miscdev);
 323 }
 324
 325 module_init(sbwdog_init);
 326 module_exit(sbwdog_exit);
 327
 328 MODULE_AUTHOR("Andrew Sharp <andy.sharp@onstor.com>");
 329 MODULE_DESCRIPTION("SiByte Watchdog");
 330
 331 module_param(timeout, ulong, 0);
 332 MODULE_PARM_DESC(timeout,
 333       "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)");
 334
 335 MODULE_LICENSE("GPL");
 336 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 337
 338 /*
 339  * example code that can be put in a platform code area to utilize the
 340  * first watchdog timer for the kernels own purpose.
 341
 342 void platform_wd_setup(void)
 343 {
 344         int ret;
 345
 346         ret = request_irq(1, sbwdog_interrupt, IRQF_DISABLED | IRQF_SHARED,
 347                 "Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0));
 348         if (ret) {
 349                 printk(KERN_CRIT
 350                   "Watchdog IRQ zero(0) failed to be requested - %d\n", ret);
 351         }
 352 }
 353
 354
 355  */