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sc520_wdt.c
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1 /*
2  * AMD Elan SC520 processor Watchdog Timer driver
3  *
4  * Based on acquirewdt.c by Alan Cox,
5  * and sbc60xxwdt.c by Jakob Oestergaard <[email protected]>
6  *
7  * This program is free software; you can redistribute it and/or
8  * modify it under the terms of the GNU General Public License
9  * as published by the Free Software Foundation; either version
10  * 2 of the License, or (at your option) any later version.
11  *
12  * The authors do NOT admit liability nor provide warranty for
13  * any of this software. This material is provided "AS-IS" in
14  * the hope that it may be useful for others.
15  *
16  * (c) Copyright 2001 Scott Jennings <[email protected]>
17  * 9/27 - 2001 [Initial release]
18  *
19  * Additional fixes Alan Cox
20  * - Fixed formatting
21  * - Removed debug printks
22  * - Fixed SMP built kernel deadlock
23  * - Switched to private locks not lock_kernel
24  * - Used ioremap/writew/readw
25  * - Added NOWAYOUT support
26  * 4/12 - 2002 Changes by Rob Radez <[email protected]>
27  * - Change comments
28  * - Eliminate fop_llseek
29  * - Change CONFIG_WATCHDOG_NOWAYOUT semantics
30  * - Add KERN_* tags to printks
31  * - fix possible wdt_is_open race
32  * - Report proper capabilities in watchdog_info
33  * - Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
34  * GETTIMEOUT, SETOPTIONS} ioctls
35  * 09/8 - 2003 Changes by Wim Van Sebroeck <[email protected]>
36  * - cleanup of trailing spaces
37  * - added extra printk's for startup problems
38  * - use module_param
39  * - made timeout (the emulated heartbeat) a module_param
40  * - made the keepalive ping an internal subroutine
41  * 3/27 - 2004 Changes by Sean Young <[email protected]>
42  * - set MMCR_BASE to 0xfffef000
43  * - CBAR does not need to be read
44  * - removed debugging printks
45  *
46  * This WDT driver is different from most other Linux WDT
47  * drivers in that the driver will ping the watchdog by itself,
48  * because this particular WDT has a very short timeout (1.6
49  * seconds) and it would be insane to count on any userspace
50  * daemon always getting scheduled within that time frame.
51  *
52  * This driver uses memory mapped IO, and spinlock.
53  */
54 
55 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
56 
57 #include <linux/module.h>
58 #include <linux/moduleparam.h>
59 #include <linux/types.h>
60 #include <linux/timer.h>
61 #include <linux/miscdevice.h>
62 #include <linux/watchdog.h>
63 #include <linux/fs.h>
64 #include <linux/ioport.h>
65 #include <linux/notifier.h>
66 #include <linux/reboot.h>
67 #include <linux/init.h>
68 #include <linux/jiffies.h>
69 #include <linux/io.h>
70 #include <linux/uaccess.h>
71 
72 
73 /*
74  * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
75  *
76  * 0: 492us 2: 1.01s 4: 4.03s 6: 16.22s
77  * 1: 503ms 3: 2.01s 5: 8.05s 7: 32.21s
78  *
79  * We will program the SC520 watchdog for a timeout of 2.01s.
80  * If we reset the watchdog every ~250ms we should be safe.
81  */
82 
83 #define WDT_INTERVAL (HZ/4+1)
84 
85 /*
86  * We must not require too good response from the userspace daemon.
87  * Here we require the userspace daemon to send us a heartbeat
88  * char to /dev/watchdog every 30 seconds.
89  */
90 
91 #define WATCHDOG_TIMEOUT 30 /* 30 sec default timeout */
92 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
93 static int timeout = WATCHDOG_TIMEOUT;
94 module_param(timeout, int, 0);
95 MODULE_PARM_DESC(timeout,
96  "Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
98 
99 static bool nowayout = WATCHDOG_NOWAYOUT;
100 module_param(nowayout, bool, 0);
101 MODULE_PARM_DESC(nowayout,
102  "Watchdog cannot be stopped once started (default="
104 
105 /*
106  * AMD Elan SC520 - Watchdog Timer Registers
107  */
108 #define MMCR_BASE 0xfffef000 /* The default base address */
109 #define OFFS_WDTMRCTL 0xCB0 /* Watchdog Timer Control Register */
110 
111 /* WDT Control Register bit definitions */
112 #define WDT_EXP_SEL_01 0x0001 /* [01] Time-out = 496 us (with 33 Mhz clk). */
113 #define WDT_EXP_SEL_02 0x0002 /* [02] Time-out = 508 ms (with 33 Mhz clk). */
114 #define WDT_EXP_SEL_03 0x0004 /* [03] Time-out = 1.02 s (with 33 Mhz clk). */
115 #define WDT_EXP_SEL_04 0x0008 /* [04] Time-out = 2.03 s (with 33 Mhz clk). */
116 #define WDT_EXP_SEL_05 0x0010 /* [05] Time-out = 4.07 s (with 33 Mhz clk). */
117 #define WDT_EXP_SEL_06 0x0020 /* [06] Time-out = 8.13 s (with 33 Mhz clk). */
118 #define WDT_EXP_SEL_07 0x0040 /* [07] Time-out = 16.27s (with 33 Mhz clk). */
119 #define WDT_EXP_SEL_08 0x0080 /* [08] Time-out = 32.54s (with 33 Mhz clk). */
120 #define WDT_IRQ_FLG 0x1000 /* [12] Interrupt Request Flag */
121 #define WDT_WRST_ENB 0x4000 /* [14] Watchdog Timer Reset Enable */
122 #define WDT_ENB 0x8000 /* [15] Watchdog Timer Enable */
123 
124 static __u16 __iomem *wdtmrctl;
125 
126 static void wdt_timer_ping(unsigned long);
127 static DEFINE_TIMER(timer, wdt_timer_ping, 0, 0);
128 static unsigned long next_heartbeat;
129 static unsigned long wdt_is_open;
130 static char wdt_expect_close;
131 static DEFINE_SPINLOCK(wdt_spinlock);
132 
133 /*
134  * Whack the dog
135  */
136 
137 static void wdt_timer_ping(unsigned long data)
138 {
139  /* If we got a heartbeat pulse within the WDT_US_INTERVAL
140  * we agree to ping the WDT
141  */
142  if (time_before(jiffies, next_heartbeat)) {
143  /* Ping the WDT */
144  spin_lock(&wdt_spinlock);
145  writew(0xAAAA, wdtmrctl);
146  writew(0x5555, wdtmrctl);
147  spin_unlock(&wdt_spinlock);
148 
149  /* Re-set the timer interval */
150  mod_timer(&timer, jiffies + WDT_INTERVAL);
151  } else
152  pr_warn("Heartbeat lost! Will not ping the watchdog\n");
153 }
154 
155 /*
156  * Utility routines
157  */
158 
159 static void wdt_config(int writeval)
160 {
161  __u16 dummy;
162  unsigned long flags;
163 
164  /* buy some time (ping) */
165  spin_lock_irqsave(&wdt_spinlock, flags);
166  dummy = readw(wdtmrctl); /* ensure write synchronization */
167  writew(0xAAAA, wdtmrctl);
168  writew(0x5555, wdtmrctl);
169  /* unlock WDT = make WDT configuration register writable one time */
170  writew(0x3333, wdtmrctl);
171  writew(0xCCCC, wdtmrctl);
172  /* write WDT configuration register */
173  writew(writeval, wdtmrctl);
174  spin_unlock_irqrestore(&wdt_spinlock, flags);
175 }
176 
177 static int wdt_startup(void)
178 {
179  next_heartbeat = jiffies + (timeout * HZ);
180 
181  /* Start the timer */
182  mod_timer(&timer, jiffies + WDT_INTERVAL);
183 
184  /* Start the watchdog */
185  wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
186 
187  pr_info("Watchdog timer is now enabled\n");
188  return 0;
189 }
190 
191 static int wdt_turnoff(void)
192 {
193  /* Stop the timer */
194  del_timer(&timer);
195 
196  /* Stop the watchdog */
197  wdt_config(0);
198 
199  pr_info("Watchdog timer is now disabled...\n");
200  return 0;
201 }
202 
203 static int wdt_keepalive(void)
204 {
205  /* user land ping */
206  next_heartbeat = jiffies + (timeout * HZ);
207  return 0;
208 }
209 
210 static int wdt_set_heartbeat(int t)
211 {
212  if ((t < 1) || (t > 3600)) /* arbitrary upper limit */
213  return -EINVAL;
214 
215  timeout = t;
216  return 0;
217 }
218 
219 /*
220  * /dev/watchdog handling
221  */
222 
223 static ssize_t fop_write(struct file *file, const char __user *buf,
224  size_t count, loff_t *ppos)
225 {
226  /* See if we got the magic character 'V' and reload the timer */
227  if (count) {
228  if (!nowayout) {
229  size_t ofs;
230 
231  /* note: just in case someone wrote the magic character
232  * five months ago... */
233  wdt_expect_close = 0;
234 
235  /* now scan */
236  for (ofs = 0; ofs != count; ofs++) {
237  char c;
238  if (get_user(c, buf + ofs))
239  return -EFAULT;
240  if (c == 'V')
241  wdt_expect_close = 42;
242  }
243  }
244 
245  /* Well, anyhow someone wrote to us, we should
246  return that favour */
247  wdt_keepalive();
248  }
249  return count;
250 }
251 
252 static int fop_open(struct inode *inode, struct file *file)
253 {
254  /* Just in case we're already talking to someone... */
255  if (test_and_set_bit(0, &wdt_is_open))
256  return -EBUSY;
257  if (nowayout)
258  __module_get(THIS_MODULE);
259 
260  /* Good, fire up the show */
261  wdt_startup();
262  return nonseekable_open(inode, file);
263 }
264 
265 static int fop_close(struct inode *inode, struct file *file)
266 {
267  if (wdt_expect_close == 42)
268  wdt_turnoff();
269  else {
270  pr_crit("Unexpected close, not stopping watchdog!\n");
271  wdt_keepalive();
272  }
273  clear_bit(0, &wdt_is_open);
274  wdt_expect_close = 0;
275  return 0;
276 }
277 
278 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
279 {
280  void __user *argp = (void __user *)arg;
281  int __user *p = argp;
282  static const struct watchdog_info ident = {
285  .firmware_version = 1,
286  .identity = "SC520",
287  };
288 
289  switch (cmd) {
290  case WDIOC_GETSUPPORT:
291  return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
292  case WDIOC_GETSTATUS:
293  case WDIOC_GETBOOTSTATUS:
294  return put_user(0, p);
295  case WDIOC_SETOPTIONS:
296  {
297  int new_options, retval = -EINVAL;
298 
299  if (get_user(new_options, p))
300  return -EFAULT;
301 
302  if (new_options & WDIOS_DISABLECARD) {
303  wdt_turnoff();
304  retval = 0;
305  }
306 
307  if (new_options & WDIOS_ENABLECARD) {
308  wdt_startup();
309  retval = 0;
310  }
311 
312  return retval;
313  }
314  case WDIOC_KEEPALIVE:
315  wdt_keepalive();
316  return 0;
317  case WDIOC_SETTIMEOUT:
318  {
319  int new_timeout;
320 
321  if (get_user(new_timeout, p))
322  return -EFAULT;
323 
324  if (wdt_set_heartbeat(new_timeout))
325  return -EINVAL;
326 
327  wdt_keepalive();
328  /* Fall through */
329  }
330  case WDIOC_GETTIMEOUT:
331  return put_user(timeout, p);
332  default:
333  return -ENOTTY;
334  }
335 }
336 
337 static const struct file_operations wdt_fops = {
338  .owner = THIS_MODULE,
339  .llseek = no_llseek,
340  .write = fop_write,
341  .open = fop_open,
342  .release = fop_close,
343  .unlocked_ioctl = fop_ioctl,
344 };
345 
346 static struct miscdevice wdt_miscdev = {
347  .minor = WATCHDOG_MINOR,
348  .name = "watchdog",
349  .fops = &wdt_fops,
350 };
351 
352 /*
353  * Notifier for system down
354  */
355 
356 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
357  void *unused)
358 {
359  if (code == SYS_DOWN || code == SYS_HALT)
360  wdt_turnoff();
361  return NOTIFY_DONE;
362 }
363 
364 /*
365  * The WDT needs to learn about soft shutdowns in order to
366  * turn the timebomb registers off.
367  */
368 
369 static struct notifier_block wdt_notifier = {
370  .notifier_call = wdt_notify_sys,
371 };
372 
373 static void __exit sc520_wdt_unload(void)
374 {
375  if (!nowayout)
376  wdt_turnoff();
377 
378  /* Deregister */
379  misc_deregister(&wdt_miscdev);
380  unregister_reboot_notifier(&wdt_notifier);
381  iounmap(wdtmrctl);
382 }
383 
384 static int __init sc520_wdt_init(void)
385 {
386  int rc = -EBUSY;
387 
388  /* Check that the timeout value is within it's range ;
389  if not reset to the default */
390  if (wdt_set_heartbeat(timeout)) {
391  wdt_set_heartbeat(WATCHDOG_TIMEOUT);
392  pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
394  }
395 
396  wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
397  if (!wdtmrctl) {
398  pr_err("Unable to remap memory\n");
399  rc = -ENOMEM;
400  goto err_out_region2;
401  }
402 
403  rc = register_reboot_notifier(&wdt_notifier);
404  if (rc) {
405  pr_err("cannot register reboot notifier (err=%d)\n", rc);
406  goto err_out_ioremap;
407  }
408 
409  rc = misc_register(&wdt_miscdev);
410  if (rc) {
411  pr_err("cannot register miscdev on minor=%d (err=%d)\n",
412  WATCHDOG_MINOR, rc);
413  goto err_out_notifier;
414  }
415 
416  pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
417  timeout, nowayout);
418 
419  return 0;
420 
421 err_out_notifier:
422  unregister_reboot_notifier(&wdt_notifier);
423 err_out_ioremap:
424  iounmap(wdtmrctl);
425 err_out_region2:
426  return rc;
427 }
428 
429 module_init(sc520_wdt_init);
430 module_exit(sc520_wdt_unload);
431 
432 MODULE_AUTHOR("Scott and Bill Jennings");
434  "Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
435 MODULE_LICENSE("GPL");