xref: /netbsd-src/sys/arch/amiga/dev/clock.c (revision 404fbe5fb94ca1e054339640cabb2801ce52dd30)
1 /*	$NetBSD: clock.c,v 1.48 2008/12/07 03:48:43 mhitch Exp $ */
2 
3 /*
4  * Copyright (c) 1982, 1990 The Regents of the University of California.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * the Systems Programming Group of the University of Utah Computer
9  * Science Department.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions and the following disclaimer.
16  * 2. Redistributions in binary form must reproduce the above copyright
17  *    notice, this list of conditions and the following disclaimer in the
18  *    documentation and/or other materials provided with the distribution.
19  * 3. Neither the name of the University nor the names of its contributors
20  *    may be used to endorse or promote products derived from this software
21  *    without specific prior written permission.
22  *
23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33  * SUCH DAMAGE.
34  *
35  * from: Utah $Hdr: clock.c 1.18 91/01/21$
36  *
37  *	@(#)clock.c	7.6 (Berkeley) 5/7/91
38  */
39 /*
40  * Copyright (c) 1988 University of Utah.
41  *
42  * This code is derived from software contributed to Berkeley by
43  * the Systems Programming Group of the University of Utah Computer
44  * Science Department.
45  *
46  * Redistribution and use in source and binary forms, with or without
47  * modification, are permitted provided that the following conditions
48  * are met:
49  * 1. Redistributions of source code must retain the above copyright
50  *    notice, this list of conditions and the following disclaimer.
51  * 2. Redistributions in binary form must reproduce the above copyright
52  *    notice, this list of conditions and the following disclaimer in the
53  *    documentation and/or other materials provided with the distribution.
54  * 3. All advertising materials mentioning features or use of this software
55  *    must display the following acknowledgement:
56  *	This product includes software developed by the University of
57  *	California, Berkeley and its contributors.
58  * 4. Neither the name of the University nor the names of its contributors
59  *    may be used to endorse or promote products derived from this software
60  *    without specific prior written permission.
61  *
62  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
63  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
64  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
65  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
66  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
67  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
68  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
69  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
70  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
71  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
72  * SUCH DAMAGE.
73  *
74  * from: Utah $Hdr: clock.c 1.18 91/01/21$
75  *
76  *	@(#)clock.c	7.6 (Berkeley) 5/7/91
77  */
78 
79 #include <sys/cdefs.h>
80 __KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.48 2008/12/07 03:48:43 mhitch Exp $");
81 
82 #include <sys/param.h>
83 #include <sys/kernel.h>
84 #include <sys/device.h>
85 #include <sys/systm.h>
86 #include <sys/timetc.h>
87 #include <machine/psl.h>
88 #include <machine/cpu.h>
89 #include <amiga/amiga/device.h>
90 #include <amiga/amiga/custom.h>
91 #include <amiga/amiga/cia.h>
92 #ifdef DRACO
93 #include <amiga/amiga/drcustom.h>
94 #include <m68k/include/asm_single.h>
95 #endif
96 #include <amiga/dev/rtc.h>
97 #include <amiga/dev/zbusvar.h>
98 
99 #if defined(PROF) && defined(PROFTIMER)
100 #include <sys/PROF.h>
101 #endif
102 
103 /* the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz.
104    We're using a 100 Hz clock. */
105 int amiga_clk_interval;
106 int eclockfreq;
107 unsigned int fast_delay_limit;
108 struct CIA *clockcia;
109 
110 static u_int clk_getcounter(struct timecounter *);
111 
112 static struct timecounter clk_timecounter = {
113 	clk_getcounter,	/* get_timecount */
114 	0,		/* no poll_pps */
115 	0x0fffu,	/* counter_mask */
116 	0,		/* frequency */
117 	"clock",	/* name, overriden later */
118 	100,		/* quality */
119 	NULL,		/* prev */
120 	NULL,		/* next */
121 };
122 
123 /*
124  * Machine-dependent clock routines.
125  *
126  * Startrtclock restarts the real-time clock, which provides
127  * hardclock interrupts to kern_clock.c.
128  *
129  * Inittodr initializes the time of day hardware which provides
130  * date functions.
131  *
132  * Resettodr restores the time of day hardware after a time change.
133  *
134  * A note on the real-time clock:
135  * We actually load the clock with amiga_clk_interval-1 instead of amiga_clk_interval.
136  * This is because the counter decrements to zero after N+1 enabled clock
137  * periods where N is the value loaded into the counter.
138  */
139 
140 int clockmatch(struct device *, struct cfdata *, void *);
141 void clockattach(struct device *, struct device *, void *);
142 void cpu_initclocks(void);
143 
144 CFATTACH_DECL(clock, sizeof(struct device),
145     clockmatch, clockattach, NULL, NULL);
146 
147 int
148 clockmatch(struct device *pdp, struct cfdata *cfp, void *auxp)
149 {
150 	if (matchname("clock", auxp))
151 		return(1);
152 	return(0);
153 }
154 
155 /*
156  * Start the real-time clock.
157  */
158 void
159 clockattach(struct device *pdp, struct device *dp, void *auxp)
160 {
161 	const char *clockchip;
162 	u_int counter_mask;
163 	unsigned short interval;
164 #ifdef DRACO
165 	u_char dracorev;
166 #endif
167 
168 #ifdef DRACO
169 	dracorev = is_draco();
170 #endif
171 
172 	if (eclockfreq == 0)
173 		eclockfreq = 715909;	/* guess NTSC */
174 
175 #ifdef DRACO
176 	if (dracorev >= 4) {
177 		if (amiga_clk_interval == 0)	/* Only do this 1st time */
178 			eclockfreq /= 7;
179 		clockchip = "QuickLogic";
180 	} else if (dracorev) {
181 		clockcia = (struct CIA *)CIAAbase;
182 		clockchip = "CIA A";
183 	} else
184 #endif
185 	{
186 		clockcia = (struct CIA *)CIABbase;
187 		clockchip = "CIA B";
188 	}
189 
190 	amiga_clk_interval = (eclockfreq / hz);
191 
192 	counter_mask = 0x8000;
193 	while (counter_mask != 0 && (counter_mask & amiga_clk_interval) == 0)
194 		counter_mask >>= 1;
195 	counter_mask -= 1;
196 
197 	clk_timecounter.tc_name = clockchip;
198 	clk_timecounter.tc_frequency = eclockfreq;
199 	clk_timecounter.tc_counter_mask = counter_mask;
200 
201 	fast_delay_limit = UINT_MAX / amiga_clk_interval;
202 
203 	if (dp != NULL) {	/* real autoconfig? */
204 		printf(": %s system hz %d hardware hz %d\n", clockchip, hz,
205 		    eclockfreq);
206 		tc_init(&clk_timecounter);
207 	}
208 
209 #ifdef DRACO
210 	if (dracorev >= 4) {
211 		/*
212 		 * can't preload anything beforehand, timer is free_running;
213 		 * but need this for delay calibration.
214 		 */
215 
216 		draco_ioct->io_timerlo = amiga_clk_interval & 0xff;
217 		draco_ioct->io_timerhi = amiga_clk_interval >> 8;
218 
219 		return;
220 	}
221 #endif
222 	/*
223 	 * stop timer A
224 	 */
225 	clockcia->cra = clockcia->cra & 0xc0;
226 	clockcia->icr = 1 << 0;		/* disable timer A interrupt */
227 	interval = clockcia->icr;		/* and make sure it's clear */
228 
229 	/*
230 	 * load interval into registers.
231          * the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz
232 	 * supprort for PAL WHEN?!?! XXX
233 	 */
234 	interval = amiga_clk_interval - 1;
235 
236 	/*
237 	 * order of setting is important !
238 	 */
239 	clockcia->talo = interval & 0xff;
240 	clockcia->tahi = interval >> 8;
241 	/*
242 	 * start timer A in continuous mode
243 	 */
244 	clockcia->cra = (clockcia->cra & 0xc0) | 1;
245 }
246 
247 void
248 cpu_initclocks(void)
249 {
250 #ifdef DRACO
251 	unsigned char dracorev;
252 	dracorev = is_draco();
253 	if (dracorev >= 4) {
254 		draco_ioct->io_timerlo = amiga_clk_interval & 0xFF;
255 		draco_ioct->io_timerhi = amiga_clk_interval >> 8;
256 		draco_ioct->io_timerrst = 0;	/* any value resets */
257 		single_inst_bset_b(draco_ioct->io_status2, DRSTAT2_TMRINTENA);
258 
259 		return;
260 	}
261 #endif
262 	/*
263 	 * enable interrupts for timer A
264 	 */
265 	clockcia->icr = (1<<7) | (1<<0);
266 
267 	/*
268 	 * start timer A in continuous shot mode
269 	 */
270 	clockcia->cra = (clockcia->cra & 0xc0) | 1;
271 
272 	/*
273 	 * and globally enable interrupts for ciab
274 	 */
275 #ifdef DRACO
276 	if (dracorev)		/* we use cia a on DraCo */
277 		single_inst_bset_b(*draco_intena, DRIRQ_INT2);
278 	else
279 #endif
280 		custom.intena = INTF_SETCLR | INTF_EXTER;
281 
282 }
283 
284 void
285 setstatclockrate(int hertz)
286 {
287 }
288 
289 /*
290  * Returns ticks  since last recorded clock "tick"
291  * (i.e. clock interrupt).
292  */
293 static u_int
294 clk_gettick(void)
295 {
296 	u_int interval;
297 	u_char hi, hi2, lo;
298 
299 #ifdef DRACO
300 	if (is_draco() >= 4) {
301 		hi2 = draco_ioct->io_chiprev;	/* latch timer */
302 		hi = draco_ioct->io_timerhi;
303 		lo = draco_ioct->io_timerlo;
304 		interval = ((hi<<8) | lo);
305 		if (interval > amiga_clk_interval)	/* timer underflow */
306 			interval = 65536 + amiga_clk_interval - interval;
307 		else
308 			interval = amiga_clk_interval - interval;
309 
310 	} else
311 #endif
312 	{
313 		hi  = clockcia->tahi;
314 		lo  = clockcia->talo;
315 		hi2 = clockcia->tahi;
316 		if (hi != hi2) {
317 			lo = clockcia->talo;
318 			hi = hi2;
319 		}
320 
321 		interval = (amiga_clk_interval - 1) - ((hi<<8) | lo);
322 
323 		/*
324 		 * should read ICR and if there's an int pending, adjust
325 		 * interval. However, since reading ICR clears the interrupt,
326 		 * we'd lose a hardclock int, and this is not tolerable.
327 		 */
328 	}
329 
330 	return interval;
331 }
332 
333 static u_int
334 clk_getcounter(struct timecounter *tc)
335 {
336 	int old_hardclock_ticks;
337 	u_int clock_tick;
338 
339 	do {
340 		old_hardclock_ticks = hardclock_ticks;
341 		clock_tick = clk_gettick();
342 	} while (old_hardclock_ticks != hardclock_ticks);
343 
344 	return old_hardclock_ticks * amiga_clk_interval + clock_tick;
345 }
346 
347 #if notyet
348 
349 /* implement this later. I'd suggest using both timers in CIA-A, they're
350    not yet used. */
351 
352 #include "clock.h"
353 #if NCLOCK > 0
354 /*
355  * /dev/clock: mappable high resolution timer.
356  *
357  * This code implements a 32-bit recycling counter (with a 4 usec period)
358  * using timers 2 & 3 on the 6840 clock chip.  The counter can be mapped
359  * RO into a user's address space to achieve low overhead (no system calls),
360  * high-precision timing.
361  *
362  * Note that timer 3 is also used for the high precision profiling timer
363  * (PROFTIMER code above).  Care should be taken when both uses are
364  * configured as only a token effort is made to avoid conflicting use.
365  */
366 #include <sys/proc.h>
367 #include <sys/resourcevar.h>
368 #include <sys/ioctl.h>
369 #include <sys/malloc.h>
370 #include <uvm/uvm_extern.h>
371 #include <amiga/amiga/clockioctl.h>
372 #include <sys/specdev.h>
373 #include <sys/vnode.h>
374 #include <sys/mman.h>
375 
376 int clockon = 0;		/* non-zero if high-res timer enabled */
377 #ifdef PROFTIMER
378 int  profprocs = 0;		/* # of procs using profiling timer */
379 #endif
380 #ifdef DEBUG
381 int clockdebug = 0;
382 #endif
383 
384 /*ARGSUSED*/
385 int
386 clockopen(dev_t dev, int flags)
387 {
388 #ifdef PROFTIMER
389 #ifdef PROF
390 	/*
391 	 * Kernel profiling enabled, give up.
392 	 */
393 	if (profiling)
394 		return(EBUSY);
395 #endif
396 	/*
397 	 * If any user processes are profiling, give up.
398 	 */
399 	if (profprocs)
400 		return(EBUSY);
401 #endif
402 	if (!clockon) {
403 		startclock();
404 		clockon++;
405 	}
406 	return(0);
407 }
408 
409 /*ARGSUSED*/
410 int
411 clockclose(dev_t dev, int flags)
412 {
413 	(void) clockunmmap(dev, (void *)0, curproc);	/* XXX */
414 	stopclock();
415 	clockon = 0;
416 	return(0);
417 }
418 
419 /*ARGSUSED*/
420 int
421 clockioctl(dev_t dev, u_long cmd, void *data, int flag, struct proc *p)
422 {
423 	int error = 0;
424 
425 	switch (cmd) {
426 
427 	case CLOCKMAP:
428 		error = clockmmap(dev, (void **)data, p);
429 		break;
430 
431 	case CLOCKUNMAP:
432 		error = clockunmmap(dev, *(void **)data, p);
433 		break;
434 
435 	case CLOCKGETRES:
436 		*(int *)data = CLK_RESOLUTION;
437 		break;
438 
439 	default:
440 		error = EINVAL;
441 		break;
442 	}
443 	return(error);
444 }
445 
446 /*ARGSUSED*/
447 void
448 clockmap(dev_t dev, int off, int prot)
449 {
450 	return((off + (INTIOBASE+CLKBASE+CLKSR-1)) >> PGSHIFT);
451 }
452 
453 int
454 clockmmap(dev_t dev, void **addrp, struct proc *p)
455 {
456 	int error;
457 	struct vnode vn;
458 	struct specinfo si;
459 	int flags;
460 
461 	flags = MAP_FILE|MAP_SHARED;
462 	if (*addrp)
463 		flags |= MAP_FIXED;
464 	else
465 		*addrp = (void *)0x1000000;	/* XXX */
466 	vn.v_type = VCHR;			/* XXX */
467 	vn.v_specinfo = &si;			/* XXX */
468 	vn.v_rdev = dev;			/* XXX */
469 	error = vm_mmap(&p->p_vmspace->vm_map, (vm_offset_t *)addrp,
470 			PAGE_SIZE, VM_PROT_ALL, flags, (void *)&vn, 0);
471 	return(error);
472 }
473 
474 int
475 clockunmmap(dev_t dev, void *addr, struct proc *p)
476 {
477 	int rv;
478 
479 	if (addr == 0)
480 		return(EINVAL);		/* XXX: how do we deal with this? */
481 	uvm_deallocate(p->p_vmspace->vm_map, (vm_offset_t)addr, PAGE_SIZE);
482 	return 0;
483 }
484 
485 void
486 startclock(void)
487 {
488 	register struct clkreg *clk = (struct clkreg *)clkstd[0];
489 
490 	clk->clk_msb2 = -1; clk->clk_lsb2 = -1;
491 	clk->clk_msb3 = -1; clk->clk_lsb3 = -1;
492 
493 	clk->clk_cr2 = CLK_CR3;
494 	clk->clk_cr3 = CLK_OENAB|CLK_8BIT;
495 	clk->clk_cr2 = CLK_CR1;
496 	clk->clk_cr1 = CLK_IENAB;
497 }
498 
499 void
500 stopclock(void)
501 {
502 	register struct clkreg *clk = (struct clkreg *)clkstd[0];
503 
504 	clk->clk_cr2 = CLK_CR3;
505 	clk->clk_cr3 = 0;
506 	clk->clk_cr2 = CLK_CR1;
507 	clk->clk_cr1 = CLK_IENAB;
508 }
509 #endif
510 
511 #endif
512 
513 
514 #ifdef PROFTIMER
515 /*
516  * This code allows the amiga kernel to use one of the extra timers on
517  * the clock chip for profiling, instead of the regular system timer.
518  * The advantage of this is that the profiling timer can be turned up to
519  * a higher interrupt rate, giving finer resolution timing. The profclock
520  * routine is called from the lev6intr in locore, and is a specialized
521  * routine that calls addupc. The overhead then is far less than if
522  * hardclock/softclock was called. Further, the context switch code in
523  * locore has been changed to turn the profile clock on/off when switching
524  * into/out of a process that is profiling (startprofclock/stopprofclock).
525  * This reduces the impact of the profiling clock on other users, and might
526  * possibly increase the accuracy of the profiling.
527  */
528 int  profint   = PRF_INTERVAL;	/* Clock ticks between interrupts */
529 int  profscale = 0;		/* Scale factor from sys clock to prof clock */
530 char profon    = 0;		/* Is profiling clock on? */
531 
532 /* profon values - do not change, locore.s assumes these values */
533 #define PRF_NONE	0x00
534 #define	PRF_USER	0x01
535 #define	PRF_KERNEL	0x80
536 
537 void
538 initprofclock(void)
539 {
540 #if NCLOCK > 0
541 	struct proc *p = curproc;		/* XXX */
542 
543 	/*
544 	 * If the high-res timer is running, force profiling off.
545 	 * Unfortunately, this gets reflected back to the user not as
546 	 * an error but as a lack of results.
547 	 */
548 	if (clockon) {
549 		p->p_stats->p_prof.pr_scale = 0;
550 		return;
551 	}
552 	/*
553 	 * Keep track of the number of user processes that are profiling
554 	 * by checking the scale value.
555 	 *
556 	 * XXX: this all assumes that the profiling code is well behaved;
557 	 * i.e. profil() is called once per process with pcscale non-zero
558 	 * to turn it on, and once with pcscale zero to turn it off.
559 	 * Also assumes you don't do any forks or execs.  Oh well, there
560 	 * is always adb...
561 	 */
562 	if (p->p_stats->p_prof.pr_scale)
563 		profprocs++;
564 	else
565 		profprocs--;
566 #endif
567 	/*
568 	 * The profile interrupt interval must be an even divisor
569 	 * of the amiga_clk_interval so that scaling from a system clock
570 	 * tick to a profile clock tick is possible using integer math.
571 	 */
572 	if (profint > amiga_clk_interval || (amiga_clk_interval % profint) != 0)
573 		profint = amiga_clk_interval;
574 	profscale = amiga_clk_interval / profint;
575 }
576 
577 void
578 startprofclock(void)
579 {
580   unsigned short interval;
581 
582   /* stop timer B */
583   clockcia->crb = clockcia->crb & 0xc0;
584 
585   /* load interval into registers.
586      the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz */
587 
588   interval = profint - 1;
589 
590   /* order of setting is important ! */
591   clockcia->tblo = interval & 0xff;
592   clockcia->tbhi = interval >> 8;
593 
594   /* enable interrupts for timer B */
595   clockcia->icr = (1<<7) | (1<<1);
596 
597   /* start timer B in continuous shot mode */
598   clockcia->crb = (clockcia->crb & 0xc0) | 1;
599 }
600 
601 void
602 stopprofclock(void)
603 {
604   /* stop timer B */
605   clockcia->crb = clockcia->crb & 0xc0;
606 }
607 
608 #ifdef PROF
609 /*
610  * profclock() is expanded in line in lev6intr() unless profiling kernel.
611  * Assumes it is called with clock interrupts blocked.
612  */
613 void
614 profclock(void *pc, int ps)
615 {
616 	/*
617 	 * Came from user mode.
618 	 * If this process is being profiled record the tick.
619 	 */
620 	if (USERMODE(ps)) {
621 		if (p->p_stats.p_prof.pr_scale)
622 			addupc(pc, &curproc->p_stats.p_prof, 1);
623 	}
624 	/*
625 	 * Came from kernel (supervisor) mode.
626 	 * If we are profiling the kernel, record the tick.
627 	 */
628 	else if (profiling < 2) {
629 		register int s = pc - s_lowpc;
630 
631 		if (s < s_textsize)
632 			kcount[s / (HISTFRACTION * sizeof (*kcount))]++;
633 	}
634 	/*
635 	 * Kernel profiling was on but has been disabled.
636 	 * Mark as no longer profiling kernel and if all profiling done,
637 	 * disable the clock.
638 	 */
639 	if (profiling && (profon & PRF_KERNEL)) {
640 		profon &= ~PRF_KERNEL;
641 		if (profon == PRF_NONE)
642 			stopprofclock();
643 	}
644 }
645 #endif
646 #endif
647 
648 void
649 delay(unsigned int n)
650 {
651 	unsigned int cur_tick, initial_tick;
652 	int remaining;
653 
654 	/*
655 	 * Read the counter first, so that the rest of the setup overhead is
656 	 * counted.
657 	 */
658 	initial_tick = clk_gettick();
659 
660 	if (amiga_clk_interval == 0) {
661 		/*
662 		 * Clock is not initialised yet,
663 		 * so just do some ad-hoc loop.
664 		 */
665 		static uint32_t dummy;
666 
667 		n *= 4;
668 		while (n--)
669 			dummy *= eclockfreq;
670 		return;
671 	}
672 
673 	if (n <= fast_delay_limit) {
674 		/*
675 		 * For unsigned arithmetic, division can be replaced with
676 		 * multiplication with the inverse and a shift.
677 		 */
678 		remaining = n * eclockfreq / 1000000;
679 	} else {
680 		/* This is a very long delay.
681 		 * Being slow here doesn't matter.
682 		 */
683 		remaining = (unsigned long long) n * eclockfreq / 1000000;
684 	}
685 
686 	while (remaining > 0) {
687 		cur_tick = clk_gettick();
688 		if (cur_tick > initial_tick)
689 			remaining -= amiga_clk_interval - (cur_tick - initial_tick);
690 		else
691 			remaining -= initial_tick - cur_tick;
692 		initial_tick = cur_tick;
693 	}
694 }
695