drivers/watchdog/sb_wdog.c

   1 /*
   2  * Watchdog driver for SiByte SB1 SoCs
   3  *
   4  * Copyright (C) 2007 OnStor, Inc. * Andrew Sharp <andy.sharp@lsi.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@lxorguk.ukuu.org.uk>,
  39  *                                              All Rights Reserved.
  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
  47 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  48
  49 #include <linux/module.h>
  50 #include <linux/io.h>
  51 #include <linux/uaccess.h>
  52 #include <linux/fs.h>
  53 #include <linux/reboot.h>
  54 #include <linux/miscdevice.h>
  55 #include <linux/watchdog.h>
  56 #include <linux/interrupt.h>
  57
  58 #include <asm/sibyte/sb1250.h>
  59 #include <asm/sibyte/sb1250_regs.h>
  60 #include <asm/sibyte/sb1250_int.h>
  61 #include <asm/sibyte/sb1250_scd.h>
  62
  63 static DEFINE_SPINLOCK(sbwd_lock);
  64
  65 /*
  66  * set the initial count value of a timer
  67  *
  68  * wdog is the iomem address of the cfg register
  69  */
  70 void sbwdog_set(char __iomem *wdog, unsigned long t)
  71 {
  72         spin_lock(&sbwd_lock);
  73         __raw_writeb(0, wdog);
  74         __raw_writeq(t & 0x7fffffUL, wdog - 0x10);
  75         spin_unlock(&sbwd_lock);
  76 }
  77
  78 /*
  79  * cause the timer to [re]load it's initial count and start counting
  80  * all over again
  81  *
  82  * wdog is the iomem address of the cfg register
  83  */
  84 void sbwdog_pet(char __iomem *wdog)
  85 {
  86         spin_lock(&sbwd_lock);
  87         __raw_writeb(__raw_readb(wdog) | 1, wdog);
  88         spin_unlock(&sbwd_lock);
  89 }
  90
  91 static unsigned long sbwdog_gate; /* keeps it to one thread only */
  92 static char __iomem *kern_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_0));
  93 static char __iomem *user_dog = (char __iomem *)(IO_BASE + (A_SCD_WDOG_CFG_1));
  94 static unsigned long timeout = 0x7fffffUL;      /* useconds: 8.3ish secs. */
  95 static int expect_close;
  96
  97 static const struct watchdog_info ident = {
  98         .options        = WDIOF_CARDRESET | WDIOF_SETTIMEOUT |
  99                                         WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE,
 100         .identity       = "SiByte Watchdog",
 101 };
 102
 103 /*
 104  * Allow only a single thread to walk the dog
 105  */
 106 static int sbwdog_open(struct inode *inode, struct file *file)
 107 {
 108         nonseekable_open(inode, file);
 109         if (test_and_set_bit(0, &sbwdog_gate))
 110                 return -EBUSY;
 111         __module_get(THIS_MODULE);
 112
 113         /*
 114          * Activate the timer
 115          */
 116         sbwdog_set(user_dog, timeout);
 117         __raw_writeb(1, user_dog);
 118
 119         return 0;
 120 }
 121
 122 /*
 123  * Put the dog back in the kennel.
 124  */
 125 static int sbwdog_release(struct inode *inode, struct file *file)
 126 {
 127         if (expect_close == 42) {
 128                 __raw_writeb(0, user_dog);
 129                 module_put(THIS_MODULE);
 130         } else {
 131                 pr_crit("%s: Unexpected close, not stopping watchdog!\n",
 132                         ident.identity);
 133                 sbwdog_pet(user_dog);
 134         }
 135         clear_bit(0, &sbwdog_gate);
 136         expect_close = 0;
 137
 138         return 0;
 139 }
 140
 141 /*
 142  * 42 - the answer
 143  */
 144 static ssize_t sbwdog_write(struct file *file, const char __user *data,
 145                         size_t len, loff_t *ppos)
 146 {
 147         int i;
 148
 149         if (len) {
 150                 /*
 151                  * restart the timer
 152                  */
 153                 expect_close = 0;
 154
 155                 for (i = 0; i != len; i++) {
 156                         char c;
 157
 158                         if (get_user(c, data + i))
 159                                 return -EFAULT;
 160                         if (c == 'V')
 161                                 expect_close = 42;
 162                 }
 163                 sbwdog_pet(user_dog);
 164         }
 165
 166         return len;
 167 }
 168
 169 static long sbwdog_ioctl(struct file *file, unsigned int cmd,
 170                                                 unsigned long arg)
 171 {
 172         int ret = -ENOTTY;
 173         unsigned long time;
 174         void __user *argp = (void __user *)arg;
 175         int __user *p = argp;
 176
 177         switch (cmd) {
 178         case WDIOC_GETSUPPORT:
 179                 ret = copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
 180                 break;
 181
 182         case WDIOC_GETSTATUS:
 183         case WDIOC_GETBOOTSTATUS:
 184                 ret = put_user(0, p);
 185                 break;
 186
 187         case WDIOC_KEEPALIVE:
 188                 sbwdog_pet(user_dog);
 189                 ret = 0;
 190                 break;
 191
 192         case WDIOC_SETTIMEOUT:
 193                 ret = get_user(time, p);
 194                 if (ret)
 195                         break;
 196
 197                 time *= 1000000;
 198                 if (time > 0x7fffffUL) {
 199                         ret = -EINVAL;
 200                         break;
 201                 }
 202                 timeout = time;
 203                 sbwdog_set(user_dog, timeout);
 204                 sbwdog_pet(user_dog);
 205
 206         case WDIOC_GETTIMEOUT:
 207                 /*
 208                  * get the remaining count from the ... count register
 209                  * which is 1*8 before the config register
 210                  */
 211                 ret = put_user((u32)__raw_readq(user_dog - 8) / 1000000, p);
 212                 break;
 213         }
 214         return ret;
 215 }
 216
 217 /*
 218  *      Notifier for system down
 219  */
 220 static int sbwdog_notify_sys(struct notifier_block *this, unsigned long code,
 221                                                                 void *erf)
 222 {
 223         if (code == SYS_DOWN || code == SYS_HALT) {
 224                 /*
 225                  * sit and sit
 226                  */
 227                 __raw_writeb(0, user_dog);
 228                 __raw_writeb(0, kern_dog);
 229         }
 230
 231         return NOTIFY_DONE;
 232 }
 233
 234 static const struct file_operations sbwdog_fops = {
 235         .owner          = THIS_MODULE,
 236         .llseek         = no_llseek,
 237         .write          = sbwdog_write,
 238         .unlocked_ioctl = sbwdog_ioctl,
 239         .open           = sbwdog_open,
 240         .release        = sbwdog_release,
 241 };
 242
 243 static struct miscdevice sbwdog_miscdev = {
 244         .minor          = WATCHDOG_MINOR,
 245         .name           = "watchdog",
 246         .fops           = &sbwdog_fops,
 247 };
 248
 249 static struct notifier_block sbwdog_notifier = {
 250         .notifier_call  = sbwdog_notify_sys,
 251 };
 252
 253 /*
 254  * interrupt handler
 255  *
 256  * doesn't do a whole lot for user, but oh so cleverly written so kernel
 257  * code can use it to re-up the watchdog, thereby saving the kernel from
 258  * having to create and maintain a timer, just to tickle another timer,
 259  * which is just so wrong.
 260  */
 261 irqreturn_t sbwdog_interrupt(int irq, void *addr)
 262 {
 263         unsigned long wd_init;
 264         char *wd_cfg_reg = (char *)addr;
 265         u8 cfg;
 266
 267         cfg = __raw_readb(wd_cfg_reg);
 268         wd_init = __raw_readq(wd_cfg_reg - 8) & 0x7fffff;
 269
 270         /*
 271          * if it's the second watchdog timer, it's for those users
 272          */
 273         if (wd_cfg_reg == user_dog)
 274                 pr_crit("%s in danger of initiating system reset "
 275                         "in %ld.%01ld seconds\n",
 276                         ident.identity,
 277                         wd_init / 1000000, (wd_init / 100000) % 10);
 278         else
 279                 cfg |= 1;
 280
 281         __raw_writeb(cfg, wd_cfg_reg);
 282
 283         return IRQ_HANDLED;
 284 }
 285
 286 static int __init sbwdog_init(void)
 287 {
 288         int ret;
 289
 290         /*
 291          * register a reboot notifier
 292          */
 293         ret = register_reboot_notifier(&sbwdog_notifier);
 294         if (ret) {
 295                 pr_err("%s: cannot register reboot notifier (err=%d)\n",
 296                        ident.identity, ret);
 297                 return ret;
 298         }
 299
 300         /*
 301          * get the resources
 302          */
 303
 304         ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED,
 305                 ident.identity, (void *)user_dog);
 306         if (ret) {
 307                 pr_err("%s: failed to request irq 1 - %d\n",
 308                        ident.identity, ret);
 309                 goto out;
 310         }
 311
 312         ret = misc_register(&sbwdog_miscdev);
 313         if (ret == 0) {
 314                 pr_info("%s: timeout is %ld.%ld secs\n",
 315                         ident.identity,
 316                         timeout / 1000000, (timeout / 100000) % 10);
 317                 return 0;
 318         }
 319         free_irq(1, (void *)user_dog);
 320 out:
 321         unregister_reboot_notifier(&sbwdog_notifier);
 322
 323         return ret;
 324 }
 325
 326 static void __exit sbwdog_exit(void)
 327 {
 328         misc_deregister(&sbwdog_miscdev);
 329         free_irq(1, (void *)user_dog);
 330         unregister_reboot_notifier(&sbwdog_notifier);
 331 }
 332
 333 module_init(sbwdog_init);
 334 module_exit(sbwdog_exit);
 335
 336 MODULE_AUTHOR("Andrew Sharp <andy.sharp@lsi.com>");
 337 MODULE_DESCRIPTION("SiByte Watchdog");
 338
 339 module_param(timeout, ulong, 0);
 340 MODULE_PARM_DESC(timeout,
 341       "Watchdog timeout in microseconds (max/default 8388607 or 8.3ish secs)");
 342
 343 MODULE_LICENSE("GPL");
 344 MODULE_ALIAS_MISCDEV(WATCHDOG_MINOR);
 345
 346 /*
 347  * example code that can be put in a platform code area to utilize the
 348  * first watchdog timer for the kernels own purpose.
 349
 350 void platform_wd_setup(void)
 351 {
 352         int ret;
 353
 354         ret = request_irq(1, sbwdog_interrupt, IRQF_SHARED,
 355                 "Kernel Watchdog", IOADDR(A_SCD_WDOG_CFG_0));
 356         if (ret) {
 357                 pr_crit("Watchdog IRQ zero(0) failed to be requested - %d\n", ret);
 358         }
 359 }
 360
 361
 362  */