1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  *	AMD Elan SC520 processor Watchdog Timer driver
4  *
5  *	Based on acquirewdt.c by Alan Cox,
6  *	     and sbc60xxwdt.c by Jakob Oestergaard <jakob@unthought.net>
7  *
8  *	The authors do NOT admit liability nor provide warranty for
9  *	any of this software. This material is provided "AS-IS" in
10  *	the hope that it may be useful for others.
11  *
12  *	(c) Copyright 2001    Scott Jennings <linuxdrivers@oro.net>
13  *           9/27 - 2001      [Initial release]
14  *
15  *	Additional fixes Alan Cox
16  *	-	Fixed formatting
17  *	-	Removed debug printks
18  *	-	Fixed SMP built kernel deadlock
19  *	-	Switched to private locks not lock_kernel
20  *	-	Used ioremap/writew/readw
21  *	-	Added NOWAYOUT support
22  *	4/12 - 2002 Changes by Rob Radez <rob@osinvestor.com>
23  *	-	Change comments
24  *	-	Eliminate fop_llseek
25  *	-	Change CONFIG_WATCHDOG_NOWAYOUT semantics
26  *	-	Add KERN_* tags to printks
27  *	-	fix possible wdt_is_open race
28  *	-	Report proper capabilities in watchdog_info
29  *	-	Add WDIOC_{GETSTATUS, GETBOOTSTATUS, SETTIMEOUT,
30  *		GETTIMEOUT, SETOPTIONS} ioctls
31  *	09/8 - 2003 Changes by Wim Van Sebroeck <wim@iguana.be>
32  *	-	cleanup of trailing spaces
33  *	-	added extra printk's for startup problems
34  *	-	use module_param
35  *	-	made timeout (the emulated heartbeat) a module_param
36  *	-	made the keepalive ping an internal subroutine
37  *	3/27 - 2004 Changes by Sean Young <sean@mess.org>
38  *	-	set MMCR_BASE to 0xfffef000
39  *	-	CBAR does not need to be read
40  *	-	removed debugging printks
41  *
42  *  This WDT driver is different from most other Linux WDT
43  *  drivers in that the driver will ping the watchdog by itself,
44  *  because this particular WDT has a very short timeout (1.6
45  *  seconds) and it would be insane to count on any userspace
46  *  daemon always getting scheduled within that time frame.
47  *
48  *  This driver uses memory mapped IO, and spinlock.
49  */
50 
51 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
52 
53 #include <linux/module.h>
54 #include <linux/moduleparam.h>
55 #include <linux/types.h>
56 #include <linux/timer.h>
57 #include <linux/miscdevice.h>
58 #include <linux/watchdog.h>
59 #include <linux/fs.h>
60 #include <linux/ioport.h>
61 #include <linux/notifier.h>
62 #include <linux/reboot.h>
63 #include <linux/init.h>
64 #include <linux/jiffies.h>
65 #include <linux/io.h>
66 #include <linux/uaccess.h>
67 
68 
69 /*
70  * The AMD Elan SC520 timeout value is 492us times a power of 2 (0-7)
71  *
72  *   0: 492us    2: 1.01s    4: 4.03s   6: 16.22s
73  *   1: 503ms    3: 2.01s    5: 8.05s   7: 32.21s
74  *
75  * We will program the SC520 watchdog for a timeout of 2.01s.
76  * If we reset the watchdog every ~250ms we should be safe.
77  */
78 
79 #define WDT_INTERVAL (HZ/4+1)
80 
81 /*
82  * We must not require too good response from the userspace daemon.
83  * Here we require the userspace daemon to send us a heartbeat
84  * char to /dev/watchdog every 30 seconds.
85  */
86 
87 #define WATCHDOG_TIMEOUT 30		/* 30 sec default timeout */
88 /* in seconds, will be multiplied by HZ to get seconds to wait for a ping */
89 static int timeout = WATCHDOG_TIMEOUT;
90 module_param(timeout, int, 0);
91 MODULE_PARM_DESC(timeout,
92 	"Watchdog timeout in seconds. (1 <= timeout <= 3600, default="
93 				__MODULE_STRING(WATCHDOG_TIMEOUT) ")");
94 
95 static bool nowayout = WATCHDOG_NOWAYOUT;
96 module_param(nowayout, bool, 0);
97 MODULE_PARM_DESC(nowayout,
98 		"Watchdog cannot be stopped once started (default="
99 				__MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
100 
101 /*
102  * AMD Elan SC520 - Watchdog Timer Registers
103  */
104 #define MMCR_BASE	0xfffef000	/* The default base address */
105 #define OFFS_WDTMRCTL	0xCB0	/* Watchdog Timer Control Register */
106 
107 /* WDT Control Register bit definitions */
108 #define WDT_EXP_SEL_01	0x0001	/* [01] Time-out = 496 us (with 33 Mhz clk). */
109 #define WDT_EXP_SEL_02	0x0002	/* [02] Time-out = 508 ms (with 33 Mhz clk). */
110 #define WDT_EXP_SEL_03	0x0004	/* [03] Time-out = 1.02 s (with 33 Mhz clk). */
111 #define WDT_EXP_SEL_04	0x0008	/* [04] Time-out = 2.03 s (with 33 Mhz clk). */
112 #define WDT_EXP_SEL_05	0x0010	/* [05] Time-out = 4.07 s (with 33 Mhz clk). */
113 #define WDT_EXP_SEL_06	0x0020	/* [06] Time-out = 8.13 s (with 33 Mhz clk). */
114 #define WDT_EXP_SEL_07	0x0040	/* [07] Time-out = 16.27s (with 33 Mhz clk). */
115 #define WDT_EXP_SEL_08	0x0080	/* [08] Time-out = 32.54s (with 33 Mhz clk). */
116 #define WDT_IRQ_FLG	0x1000	/* [12] Interrupt Request Flag */
117 #define WDT_WRST_ENB	0x4000	/* [14] Watchdog Timer Reset Enable */
118 #define WDT_ENB		0x8000	/* [15] Watchdog Timer Enable */
119 
120 static __u16 __iomem *wdtmrctl;
121 
122 static void wdt_timer_ping(struct timer_list *);
123 static DEFINE_TIMER(timer, wdt_timer_ping);
124 static unsigned long next_heartbeat;
125 static unsigned long wdt_is_open;
126 static char wdt_expect_close;
127 static DEFINE_SPINLOCK(wdt_spinlock);
128 
129 /*
130  *	Whack the dog
131  */
132 
wdt_timer_ping(struct timer_list * unused)133 static void wdt_timer_ping(struct timer_list *unused)
134 {
135 	/* If we got a heartbeat pulse within the WDT_US_INTERVAL
136 	 * we agree to ping the WDT
137 	 */
138 	if (time_before(jiffies, next_heartbeat)) {
139 		/* Ping the WDT */
140 		spin_lock(&wdt_spinlock);
141 		writew(0xAAAA, wdtmrctl);
142 		writew(0x5555, wdtmrctl);
143 		spin_unlock(&wdt_spinlock);
144 
145 		/* Re-set the timer interval */
146 		mod_timer(&timer, jiffies + WDT_INTERVAL);
147 	} else
148 		pr_warn("Heartbeat lost! Will not ping the watchdog\n");
149 }
150 
151 /*
152  *	Utility routines
153  */
154 
wdt_config(int writeval)155 static void wdt_config(int writeval)
156 {
157 	unsigned long flags;
158 
159 	/* buy some time (ping) */
160 	spin_lock_irqsave(&wdt_spinlock, flags);
161 	readw(wdtmrctl);	/* ensure write synchronization */
162 	writew(0xAAAA, wdtmrctl);
163 	writew(0x5555, wdtmrctl);
164 	/* unlock WDT = make WDT configuration register writable one time */
165 	writew(0x3333, wdtmrctl);
166 	writew(0xCCCC, wdtmrctl);
167 	/* write WDT configuration register */
168 	writew(writeval, wdtmrctl);
169 	spin_unlock_irqrestore(&wdt_spinlock, flags);
170 }
171 
wdt_startup(void)172 static int wdt_startup(void)
173 {
174 	next_heartbeat = jiffies + (timeout * HZ);
175 
176 	/* Start the timer */
177 	mod_timer(&timer, jiffies + WDT_INTERVAL);
178 
179 	/* Start the watchdog */
180 	wdt_config(WDT_ENB | WDT_WRST_ENB | WDT_EXP_SEL_04);
181 
182 	pr_info("Watchdog timer is now enabled\n");
183 	return 0;
184 }
185 
wdt_turnoff(void)186 static int wdt_turnoff(void)
187 {
188 	/* Stop the timer */
189 	del_timer_sync(&timer);
190 
191 	/* Stop the watchdog */
192 	wdt_config(0);
193 
194 	pr_info("Watchdog timer is now disabled...\n");
195 	return 0;
196 }
197 
wdt_keepalive(void)198 static int wdt_keepalive(void)
199 {
200 	/* user land ping */
201 	next_heartbeat = jiffies + (timeout * HZ);
202 	return 0;
203 }
204 
wdt_set_heartbeat(int t)205 static int wdt_set_heartbeat(int t)
206 {
207 	if ((t < 1) || (t > 3600))	/* arbitrary upper limit */
208 		return -EINVAL;
209 
210 	timeout = t;
211 	return 0;
212 }
213 
214 /*
215  *	/dev/watchdog handling
216  */
217 
fop_write(struct file * file,const char __user * buf,size_t count,loff_t * ppos)218 static ssize_t fop_write(struct file *file, const char __user *buf,
219 						size_t count, loff_t *ppos)
220 {
221 	/* See if we got the magic character 'V' and reload the timer */
222 	if (count) {
223 		if (!nowayout) {
224 			size_t ofs;
225 
226 			/* note: just in case someone wrote the magic character
227 			 * five months ago... */
228 			wdt_expect_close = 0;
229 
230 			/* now scan */
231 			for (ofs = 0; ofs != count; ofs++) {
232 				char c;
233 				if (get_user(c, buf + ofs))
234 					return -EFAULT;
235 				if (c == 'V')
236 					wdt_expect_close = 42;
237 			}
238 		}
239 
240 		/* Well, anyhow someone wrote to us, we should
241 		   return that favour */
242 		wdt_keepalive();
243 	}
244 	return count;
245 }
246 
fop_open(struct inode * inode,struct file * file)247 static int fop_open(struct inode *inode, struct file *file)
248 {
249 	/* Just in case we're already talking to someone... */
250 	if (test_and_set_bit(0, &wdt_is_open))
251 		return -EBUSY;
252 	if (nowayout)
253 		__module_get(THIS_MODULE);
254 
255 	/* Good, fire up the show */
256 	wdt_startup();
257 	return stream_open(inode, file);
258 }
259 
fop_close(struct inode * inode,struct file * file)260 static int fop_close(struct inode *inode, struct file *file)
261 {
262 	if (wdt_expect_close == 42)
263 		wdt_turnoff();
264 	else {
265 		pr_crit("Unexpected close, not stopping watchdog!\n");
266 		wdt_keepalive();
267 	}
268 	clear_bit(0, &wdt_is_open);
269 	wdt_expect_close = 0;
270 	return 0;
271 }
272 
fop_ioctl(struct file * file,unsigned int cmd,unsigned long arg)273 static long fop_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
274 {
275 	void __user *argp = (void __user *)arg;
276 	int __user *p = argp;
277 	static const struct watchdog_info ident = {
278 		.options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT
279 							| WDIOF_MAGICCLOSE,
280 		.firmware_version = 1,
281 		.identity = "SC520",
282 	};
283 
284 	switch (cmd) {
285 	case WDIOC_GETSUPPORT:
286 		return copy_to_user(argp, &ident, sizeof(ident)) ? -EFAULT : 0;
287 	case WDIOC_GETSTATUS:
288 	case WDIOC_GETBOOTSTATUS:
289 		return put_user(0, p);
290 	case WDIOC_SETOPTIONS:
291 	{
292 		int new_options, retval = -EINVAL;
293 
294 		if (get_user(new_options, p))
295 			return -EFAULT;
296 
297 		if (new_options & WDIOS_DISABLECARD) {
298 			wdt_turnoff();
299 			retval = 0;
300 		}
301 
302 		if (new_options & WDIOS_ENABLECARD) {
303 			wdt_startup();
304 			retval = 0;
305 		}
306 
307 		return retval;
308 	}
309 	case WDIOC_KEEPALIVE:
310 		wdt_keepalive();
311 		return 0;
312 	case WDIOC_SETTIMEOUT:
313 	{
314 		int new_timeout;
315 
316 		if (get_user(new_timeout, p))
317 			return -EFAULT;
318 
319 		if (wdt_set_heartbeat(new_timeout))
320 			return -EINVAL;
321 
322 		wdt_keepalive();
323 	}
324 		fallthrough;
325 	case WDIOC_GETTIMEOUT:
326 		return put_user(timeout, p);
327 	default:
328 		return -ENOTTY;
329 	}
330 }
331 
332 static const struct file_operations wdt_fops = {
333 	.owner		= THIS_MODULE,
334 	.llseek		= no_llseek,
335 	.write		= fop_write,
336 	.open		= fop_open,
337 	.release	= fop_close,
338 	.unlocked_ioctl	= fop_ioctl,
339 	.compat_ioctl	= compat_ptr_ioctl,
340 };
341 
342 static struct miscdevice wdt_miscdev = {
343 	.minor	= WATCHDOG_MINOR,
344 	.name	= "watchdog",
345 	.fops	= &wdt_fops,
346 };
347 
348 /*
349  *	Notifier for system down
350  */
351 
wdt_notify_sys(struct notifier_block * this,unsigned long code,void * unused)352 static int wdt_notify_sys(struct notifier_block *this, unsigned long code,
353 	void *unused)
354 {
355 	if (code == SYS_DOWN || code == SYS_HALT)
356 		wdt_turnoff();
357 	return NOTIFY_DONE;
358 }
359 
360 /*
361  *	The WDT needs to learn about soft shutdowns in order to
362  *	turn the timebomb registers off.
363  */
364 
365 static struct notifier_block wdt_notifier = {
366 	.notifier_call = wdt_notify_sys,
367 };
368 
sc520_wdt_unload(void)369 static void __exit sc520_wdt_unload(void)
370 {
371 	if (!nowayout)
372 		wdt_turnoff();
373 
374 	/* Deregister */
375 	misc_deregister(&wdt_miscdev);
376 	unregister_reboot_notifier(&wdt_notifier);
377 	iounmap(wdtmrctl);
378 }
379 
sc520_wdt_init(void)380 static int __init sc520_wdt_init(void)
381 {
382 	int rc = -EBUSY;
383 
384 	/* Check that the timeout value is within it's range ;
385 	   if not reset to the default */
386 	if (wdt_set_heartbeat(timeout)) {
387 		wdt_set_heartbeat(WATCHDOG_TIMEOUT);
388 		pr_info("timeout value must be 1 <= timeout <= 3600, using %d\n",
389 			WATCHDOG_TIMEOUT);
390 	}
391 
392 	wdtmrctl = ioremap(MMCR_BASE + OFFS_WDTMRCTL, 2);
393 	if (!wdtmrctl) {
394 		pr_err("Unable to remap memory\n");
395 		rc = -ENOMEM;
396 		goto err_out_region2;
397 	}
398 
399 	rc = register_reboot_notifier(&wdt_notifier);
400 	if (rc) {
401 		pr_err("cannot register reboot notifier (err=%d)\n", rc);
402 		goto err_out_ioremap;
403 	}
404 
405 	rc = misc_register(&wdt_miscdev);
406 	if (rc) {
407 		pr_err("cannot register miscdev on minor=%d (err=%d)\n",
408 		       WATCHDOG_MINOR, rc);
409 		goto err_out_notifier;
410 	}
411 
412 	pr_info("WDT driver for SC520 initialised. timeout=%d sec (nowayout=%d)\n",
413 		timeout, nowayout);
414 
415 	return 0;
416 
417 err_out_notifier:
418 	unregister_reboot_notifier(&wdt_notifier);
419 err_out_ioremap:
420 	iounmap(wdtmrctl);
421 err_out_region2:
422 	return rc;
423 }
424 
425 module_init(sc520_wdt_init);
426 module_exit(sc520_wdt_unload);
427 
428 MODULE_AUTHOR("Scott and Bill Jennings");
429 MODULE_DESCRIPTION(
430 	"Driver for watchdog timer in AMD \"Elan\" SC520 uProcessor");
431 MODULE_LICENSE("GPL");
432