time.c 17.1 KB
Newer Older
Linus Torvalds's avatar
Linus Torvalds committed
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
/* $Id: time.c,v 1.60 2002/01/23 14:33:55 davem Exp $
 * linux/arch/sparc/kernel/time.c
 *
 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
 * Copyright (C) 1996 Thomas K. Dyas (tdyas@eden.rutgers.edu)
 *
 * Chris Davis (cdavis@cois.on.ca) 03/27/1998
 * Added support for the intersil on the sun4/4200
 *
 * Gleb Raiko (rajko@mech.math.msu.su) 08/18/1998
 * Support for MicroSPARC-IIep, PCI CPU.
 *
 * This file handles the Sparc specific time handling details.
 *
 * 1997-09-10	Updated NTP code according to technical memorandum Jan '96
 *		"A Kernel Model for Precision Timekeeping" by Dave Mills
 */
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/time.h>
#include <linux/timex.h>
#include <linux/init.h>
#include <linux/pci.h>
#include <linux/ioport.h>
#include <linux/profile.h>

#include <asm/oplib.h>
#include <asm/timer.h>
#include <asm/mostek.h>
#include <asm/system.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/idprom.h>
#include <asm/machines.h>
#include <asm/sun4paddr.h>
#include <asm/page.h>
#include <asm/pcic.h>

extern unsigned long wall_jiffies;

DEFINE_SPINLOCK(rtc_lock);
enum sparc_clock_type sp_clock_typ;
DEFINE_SPINLOCK(mostek_lock);
void __iomem *mstk48t02_regs = NULL;
52
static struct mostek48t08 __iomem *mstk48t08_regs = NULL;
Linus Torvalds's avatar
Linus Torvalds committed
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
static int set_rtc_mmss(unsigned long);
static int sbus_do_settimeofday(struct timespec *tv);

#ifdef CONFIG_SUN4
struct intersil *intersil_clock;
#define intersil_cmd(intersil_reg, intsil_cmd) intersil_reg->int_cmd_reg = \
	(intsil_cmd)

#define intersil_intr(intersil_reg, intsil_cmd) intersil_reg->int_intr_reg = \
	(intsil_cmd)

#define intersil_start(intersil_reg) intersil_cmd(intersil_reg, \
	( INTERSIL_START | INTERSIL_32K | INTERSIL_NORMAL | INTERSIL_24H |\
	  INTERSIL_INTR_ENABLE))

#define intersil_stop(intersil_reg) intersil_cmd(intersil_reg, \
	( INTERSIL_STOP | INTERSIL_32K | INTERSIL_NORMAL | INTERSIL_24H |\
	  INTERSIL_INTR_ENABLE))

#define intersil_read_intr(intersil_reg, towhere) towhere = \
	intersil_reg->int_intr_reg

#endif

unsigned long profile_pc(struct pt_regs *regs)
{
	extern char __copy_user_begin[], __copy_user_end[];
	extern char __atomic_begin[], __atomic_end[];
	extern char __bzero_begin[], __bzero_end[];
	extern char __bitops_begin[], __bitops_end[];

	unsigned long pc = regs->pc;

	if (in_lock_functions(pc) ||
	    (pc >= (unsigned long) __copy_user_begin &&
	     pc < (unsigned long) __copy_user_end) ||
	    (pc >= (unsigned long) __atomic_begin &&
	     pc < (unsigned long) __atomic_end) ||
	    (pc >= (unsigned long) __bzero_begin &&
	     pc < (unsigned long) __bzero_end) ||
	    (pc >= (unsigned long) __bitops_begin &&
	     pc < (unsigned long) __bitops_end))
		pc = regs->u_regs[UREG_RETPC];
	return pc;
}

__volatile__ unsigned int *master_l10_counter;
__volatile__ unsigned int *master_l10_limit;

/*
 * timer_interrupt() needs to keep up the real-time clock,
 * as well as call the "do_timer()" routine every clocktick
 */

#define TICK_SIZE (tick_nsec / 1000)

irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs * regs)
{
	/* last time the cmos clock got updated */
	static long last_rtc_update;

#ifndef CONFIG_SMP
	profile_tick(CPU_PROFILING, regs);
#endif

	/* Protect counter clear so that do_gettimeoffset works */
	write_seqlock(&xtime_lock);
#ifdef CONFIG_SUN4
	if((idprom->id_machtype == (SM_SUN4 | SM_4_260)) ||
	   (idprom->id_machtype == (SM_SUN4 | SM_4_110))) {
		int temp;
        	intersil_read_intr(intersil_clock, temp);
		/* re-enable the irq */
		enable_pil_irq(10);
	}
#endif
	clear_clock_irq();

	do_timer(regs);
#ifndef CONFIG_SMP
	update_process_times(user_mode(regs));
#endif


	/* Determine when to update the Mostek clock. */
138
	if (ntp_synced() &&
Linus Torvalds's avatar
Linus Torvalds committed
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
	    xtime.tv_sec > last_rtc_update + 660 &&
	    (xtime.tv_nsec / 1000) >= 500000 - ((unsigned) TICK_SIZE) / 2 &&
	    (xtime.tv_nsec / 1000) <= 500000 + ((unsigned) TICK_SIZE) / 2) {
	  if (set_rtc_mmss(xtime.tv_sec) == 0)
	    last_rtc_update = xtime.tv_sec;
	  else
	    last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
	}
	write_sequnlock(&xtime_lock);

	return IRQ_HANDLED;
}

/* Kick start a stopped clock (procedure from the Sun NVRAM/hostid FAQ). */
static void __init kick_start_clock(void)
{
	struct mostek48t02 *regs = (struct mostek48t02 *)mstk48t02_regs;
	unsigned char sec;
	int i, count;

	prom_printf("CLOCK: Clock was stopped. Kick start ");

	spin_lock_irq(&mostek_lock);

	/* Turn on the kick start bit to start the oscillator. */
	regs->creg |= MSTK_CREG_WRITE;
	regs->sec &= ~MSTK_STOP;
	regs->hour |= MSTK_KICK_START;
	regs->creg &= ~MSTK_CREG_WRITE;

	spin_unlock_irq(&mostek_lock);

	/* Delay to allow the clock oscillator to start. */
	sec = MSTK_REG_SEC(regs);
	for (i = 0; i < 3; i++) {
		while (sec == MSTK_REG_SEC(regs))
			for (count = 0; count < 100000; count++)
				/* nothing */ ;
		prom_printf(".");
		sec = regs->sec;
	}
	prom_printf("\n");

	spin_lock_irq(&mostek_lock);

	/* Turn off kick start and set a "valid" time and date. */
	regs->creg |= MSTK_CREG_WRITE;
	regs->hour &= ~MSTK_KICK_START;
	MSTK_SET_REG_SEC(regs,0);
	MSTK_SET_REG_MIN(regs,0);
	MSTK_SET_REG_HOUR(regs,0);
	MSTK_SET_REG_DOW(regs,5);
	MSTK_SET_REG_DOM(regs,1);
	MSTK_SET_REG_MONTH(regs,8);
	MSTK_SET_REG_YEAR(regs,1996 - MSTK_YEAR_ZERO);
	regs->creg &= ~MSTK_CREG_WRITE;

	spin_unlock_irq(&mostek_lock);

	/* Ensure the kick start bit is off. If it isn't, turn it off. */
	while (regs->hour & MSTK_KICK_START) {
		prom_printf("CLOCK: Kick start still on!\n");

		spin_lock_irq(&mostek_lock);
		regs->creg |= MSTK_CREG_WRITE;
		regs->hour &= ~MSTK_KICK_START;
		regs->creg &= ~MSTK_CREG_WRITE;
		spin_unlock_irq(&mostek_lock);
	}

	prom_printf("CLOCK: Kick start procedure successful.\n");
}

/* Return nonzero if the clock chip battery is low. */
static __inline__ int has_low_battery(void)
{
	struct mostek48t02 *regs = (struct mostek48t02 *)mstk48t02_regs;
	unsigned char data1, data2;

	spin_lock_irq(&mostek_lock);
	data1 = regs->eeprom[0];	/* Read some data. */
	regs->eeprom[0] = ~data1;	/* Write back the complement. */
	data2 = regs->eeprom[0];	/* Read back the complement. */
	regs->eeprom[0] = data1;	/* Restore the original value. */
	spin_unlock_irq(&mostek_lock);

	return (data1 == data2);	/* Was the write blocked? */
}

/* Probe for the real time clock chip on Sun4 */
static __inline__ void sun4_clock_probe(void)
{
#ifdef CONFIG_SUN4
	int temp;
	struct resource r;

	memset(&r, 0, sizeof(r));
	if( idprom->id_machtype == (SM_SUN4 | SM_4_330) ) {
		sp_clock_typ = MSTK48T02;
		r.start = sun4_clock_physaddr;
		mstk48t02_regs = sbus_ioremap(&r, 0,
				       sizeof(struct mostek48t02), NULL);
		mstk48t08_regs = NULL;  /* To catch weirdness */
		intersil_clock = NULL;  /* just in case */

		/* Kick start the clock if it is completely stopped. */
		if (mostek_read(mstk48t02_regs + MOSTEK_SEC) & MSTK_STOP)
			kick_start_clock();
	} else if( idprom->id_machtype == (SM_SUN4 | SM_4_260)) {
		/* intersil setup code */
		printk("Clock: INTERSIL at %8x ",sun4_clock_physaddr);
		sp_clock_typ = INTERSIL;
		r.start = sun4_clock_physaddr;
		intersil_clock = (struct intersil *) 
		    sbus_ioremap(&r, 0, sizeof(*intersil_clock), "intersil");
		mstk48t02_regs = 0;  /* just be sure */
		mstk48t08_regs = NULL;  /* ditto */
		/* initialise the clock */

		intersil_intr(intersil_clock,INTERSIL_INT_100HZ);

		intersil_start(intersil_clock);

		intersil_read_intr(intersil_clock, temp);
                while (!(temp & 0x80))
                        intersil_read_intr(intersil_clock, temp);

                intersil_read_intr(intersil_clock, temp);
                while (!(temp & 0x80))
                        intersil_read_intr(intersil_clock, temp);

		intersil_stop(intersil_clock);

	}
#endif
}

/* Probe for the mostek real time clock chip. */
static __inline__ void clock_probe(void)
{
	struct linux_prom_registers clk_reg[2];
	char model[128];
	register int node, cpuunit, bootbus;
	struct resource r;

	cpuunit = bootbus = 0;
	memset(&r, 0, sizeof(r));

	/* Determine the correct starting PROM node for the probe. */
	node = prom_getchild(prom_root_node);
	switch (sparc_cpu_model) {
	case sun4c:
		break;
	case sun4m:
		node = prom_getchild(prom_searchsiblings(node, "obio"));
		break;
	case sun4d:
		node = prom_getchild(bootbus = prom_searchsiblings(prom_getchild(cpuunit = prom_searchsiblings(node, "cpu-unit")), "bootbus"));
		break;
	default:
		prom_printf("CLOCK: Unsupported architecture!\n");
		prom_halt();
	}

	/* Find the PROM node describing the real time clock. */
	sp_clock_typ = MSTK_INVALID;
	node = prom_searchsiblings(node,"eeprom");
	if (!node) {
		prom_printf("CLOCK: No clock found!\n");
		prom_halt();
	}

	/* Get the model name and setup everything up. */
	model[0] = '\0';
	prom_getstring(node, "model", model, sizeof(model));
	if (strcmp(model, "mk48t02") == 0) {
		sp_clock_typ = MSTK48T02;
		if (prom_getproperty(node, "reg", (char *) clk_reg, sizeof(clk_reg)) == -1) {
			prom_printf("clock_probe: FAILED!\n");
			prom_halt();
		}
		if (sparc_cpu_model == sun4d)
			prom_apply_generic_ranges (bootbus, cpuunit, clk_reg, 1);
		else
			prom_apply_obio_ranges(clk_reg, 1);
		/* Map the clock register io area read-only */
		r.flags = clk_reg[0].which_io;
		r.start = clk_reg[0].phys_addr;
		mstk48t02_regs = sbus_ioremap(&r, 0,
		    sizeof(struct mostek48t02), "mk48t02");
		mstk48t08_regs = NULL;  /* To catch weirdness */
	} else if (strcmp(model, "mk48t08") == 0) {
		sp_clock_typ = MSTK48T08;
		if(prom_getproperty(node, "reg", (char *) clk_reg,
				    sizeof(clk_reg)) == -1) {
			prom_printf("clock_probe: FAILED!\n");
			prom_halt();
		}
		if (sparc_cpu_model == sun4d)
			prom_apply_generic_ranges (bootbus, cpuunit, clk_reg, 1);
		else
			prom_apply_obio_ranges(clk_reg, 1);
		/* Map the clock register io area read-only */
		/* XXX r/o attribute is somewhere in r.flags */
		r.flags = clk_reg[0].which_io;
		r.start = clk_reg[0].phys_addr;
345
		mstk48t08_regs = sbus_ioremap(&r, 0,
Linus Torvalds's avatar
Linus Torvalds committed
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
		    sizeof(struct mostek48t08), "mk48t08");

		mstk48t02_regs = &mstk48t08_regs->regs;
	} else {
		prom_printf("CLOCK: Unknown model name '%s'\n",model);
		prom_halt();
	}

	/* Report a low battery voltage condition. */
	if (has_low_battery())
		printk(KERN_CRIT "NVRAM: Low battery voltage!\n");

	/* Kick start the clock if it is completely stopped. */
	if (mostek_read(mstk48t02_regs + MOSTEK_SEC) & MSTK_STOP)
		kick_start_clock();
}

void __init sbus_time_init(void)
{
	unsigned int year, mon, day, hour, min, sec;
	struct mostek48t02 *mregs;

#ifdef CONFIG_SUN4
	int temp;
	struct intersil *iregs;
#endif

	BTFIXUPSET_CALL(bus_do_settimeofday, sbus_do_settimeofday, BTFIXUPCALL_NORM);
	btfixup();

	if (ARCH_SUN4)
		sun4_clock_probe();
	else
		clock_probe();

	sparc_init_timers(timer_interrupt);
	
#ifdef CONFIG_SUN4
	if(idprom->id_machtype == (SM_SUN4 | SM_4_330)) {
#endif
	mregs = (struct mostek48t02 *)mstk48t02_regs;
	if(!mregs) {
		prom_printf("Something wrong, clock regs not mapped yet.\n");
		prom_halt();
	}		
	spin_lock_irq(&mostek_lock);
	mregs->creg |= MSTK_CREG_READ;
	sec = MSTK_REG_SEC(mregs);
	min = MSTK_REG_MIN(mregs);
	hour = MSTK_REG_HOUR(mregs);
	day = MSTK_REG_DOM(mregs);
	mon = MSTK_REG_MONTH(mregs);
	year = MSTK_CVT_YEAR( MSTK_REG_YEAR(mregs) );
	xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
	xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
        set_normalized_timespec(&wall_to_monotonic,
                                -xtime.tv_sec, -xtime.tv_nsec);
	mregs->creg &= ~MSTK_CREG_READ;
	spin_unlock_irq(&mostek_lock);
#ifdef CONFIG_SUN4
	} else if(idprom->id_machtype == (SM_SUN4 | SM_4_260) ) {
		/* initialise the intersil on sun4 */

		iregs=intersil_clock;
		if(!iregs) {
			prom_printf("Something wrong, clock regs not mapped yet.\n");
			prom_halt();
		}

		intersil_intr(intersil_clock,INTERSIL_INT_100HZ);
		disable_pil_irq(10);
		intersil_stop(iregs);
		intersil_read_intr(intersil_clock, temp);

		temp = iregs->clk.int_csec;

		sec = iregs->clk.int_sec;
		min = iregs->clk.int_min;
		hour = iregs->clk.int_hour;
		day = iregs->clk.int_day;
		mon = iregs->clk.int_month;
		year = MSTK_CVT_YEAR(iregs->clk.int_year);

		enable_pil_irq(10);
		intersil_start(iregs);

		xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
		xtime.tv_nsec = (INITIAL_JIFFIES % HZ) * (NSEC_PER_SEC / HZ);
	        set_normalized_timespec(&wall_to_monotonic,
 	                               -xtime.tv_sec, -xtime.tv_nsec);
		printk("%u/%u/%u %u:%u:%u\n",day,mon,year,hour,min,sec);
	}
#endif

	/* Now that OBP ticker has been silenced, it is safe to enable IRQ. */
	local_irq_enable();
}

void __init time_init(void)
{
#ifdef CONFIG_PCI
	extern void pci_time_init(void);
	if (pcic_present()) {
		pci_time_init();
		return;
	}
#endif
	sbus_time_init();
}

456
static inline unsigned long do_gettimeoffset(void)
Linus Torvalds's avatar
Linus Torvalds committed
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
{
	return (*master_l10_counter >> 10) & 0x1fffff;
}

/*
 * Returns nanoseconds
 * XXX This is a suboptimal implementation.
 */
unsigned long long sched_clock(void)
{
	return (unsigned long long)jiffies * (1000000000 / HZ);
}

/* Ok, my cute asm atomicity trick doesn't work anymore.
 * There are just too many variables that need to be protected
 * now (both members of xtime, wall_jiffies, et al.)
 */
void do_gettimeofday(struct timeval *tv)
{
	unsigned long flags;
	unsigned long seq;
	unsigned long usec, sec;
	unsigned long max_ntp_tick = tick_usec - tickadj;

	do {
		unsigned long lost;

		seq = read_seqbegin_irqsave(&xtime_lock, flags);
		usec = do_gettimeoffset();
		lost = jiffies - wall_jiffies;

		/*
		 * If time_adjust is negative then NTP is slowing the clock
		 * so make sure not to go into next possible interval.
		 * Better to lose some accuracy than have time go backwards..
		 */
		if (unlikely(time_adjust < 0)) {
			usec = min(usec, max_ntp_tick);

			if (lost)
				usec += lost * max_ntp_tick;
		}
		else if (unlikely(lost))
			usec += lost * tick_usec;

		sec = xtime.tv_sec;
		usec += (xtime.tv_nsec / 1000);
	} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));

	while (usec >= 1000000) {
		usec -= 1000000;
		sec++;
	}

	tv->tv_sec = sec;
	tv->tv_usec = usec;
}

EXPORT_SYMBOL(do_gettimeofday);

int do_settimeofday(struct timespec *tv)
{
	int ret;

	write_seqlock_irq(&xtime_lock);
	ret = bus_do_settimeofday(tv);
	write_sequnlock_irq(&xtime_lock);
	clock_was_set();
	return ret;
}

EXPORT_SYMBOL(do_settimeofday);

static int sbus_do_settimeofday(struct timespec *tv)
{
	time_t wtm_sec, sec = tv->tv_sec;
	long wtm_nsec, nsec = tv->tv_nsec;

	if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
		return -EINVAL;

	/*
	 * This is revolting. We need to set "xtime" correctly. However, the
	 * value in this location is the value at the most recent update of
	 * wall time.  Discover what correction gettimeofday() would have
	 * made, and then undo it!
	 */
	nsec -= 1000 * (do_gettimeoffset() +
			(jiffies - wall_jiffies) * (USEC_PER_SEC / HZ));

	wtm_sec  = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
	wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);

	set_normalized_timespec(&xtime, sec, nsec);
	set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);

553
	ntp_clear();
Linus Torvalds's avatar
Linus Torvalds committed
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
	return 0;
}

/*
 * BUG: This routine does not handle hour overflow properly; it just
 *      sets the minutes. Usually you won't notice until after reboot!
 */
static int set_rtc_mmss(unsigned long nowtime)
{
	int real_seconds, real_minutes, mostek_minutes;
	struct mostek48t02 *regs = (struct mostek48t02 *)mstk48t02_regs;
	unsigned long flags;
#ifdef CONFIG_SUN4
	struct intersil *iregs = intersil_clock;
	int temp;
#endif

	/* Not having a register set can lead to trouble. */
	if (!regs) {
#ifdef CONFIG_SUN4
		if(!iregs)
		return -1;
	 	else {
			temp = iregs->clk.int_csec;

			mostek_minutes = iregs->clk.int_min;

			real_seconds = nowtime % 60;
			real_minutes = nowtime / 60;
			if (((abs(real_minutes - mostek_minutes) + 15)/30) & 1)
				real_minutes += 30;	/* correct for half hour time zone */
			real_minutes %= 60;

			if (abs(real_minutes - mostek_minutes) < 30) {
				intersil_stop(iregs);
				iregs->clk.int_sec=real_seconds;
				iregs->clk.int_min=real_minutes;
				intersil_start(iregs);
			} else {
				printk(KERN_WARNING
			       "set_rtc_mmss: can't update from %d to %d\n",
				       mostek_minutes, real_minutes);
				return -1;
			}
			
			return 0;
		}
#endif
	}

	spin_lock_irqsave(&mostek_lock, flags);
	/* Read the current RTC minutes. */
	regs->creg |= MSTK_CREG_READ;
	mostek_minutes = MSTK_REG_MIN(regs);
	regs->creg &= ~MSTK_CREG_READ;

	/*
	 * since we're only adjusting minutes and seconds,
	 * don't interfere with hour overflow. This avoids
	 * messing with unknown time zones but requires your
	 * RTC not to be off by more than 15 minutes
	 */
	real_seconds = nowtime % 60;
	real_minutes = nowtime / 60;
	if (((abs(real_minutes - mostek_minutes) + 15)/30) & 1)
		real_minutes += 30;	/* correct for half hour time zone */
	real_minutes %= 60;

	if (abs(real_minutes - mostek_minutes) < 30) {
		regs->creg |= MSTK_CREG_WRITE;
		MSTK_SET_REG_SEC(regs,real_seconds);
		MSTK_SET_REG_MIN(regs,real_minutes);
		regs->creg &= ~MSTK_CREG_WRITE;
		spin_unlock_irqrestore(&mostek_lock, flags);
		return 0;
	} else {
		spin_unlock_irqrestore(&mostek_lock, flags);
		return -1;
	}
}