xref: /netbsd-src/sys/arch/amiga/dev/clock.c (revision 6deb2c22d20de1d75d538e8a5c57b573926fd157)
1 /*	$NetBSD: clock.c,v 1.50 2009/09/11 19:43:08 phx 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 1.50 2009/09/11 19:43:08 phx 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 	~0u,		/* 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 	unsigned short interval;
163 #ifdef DRACO
164 	u_char dracorev;
165 #endif
166 
167 #ifdef DRACO
168 	dracorev = is_draco();
169 #endif
170 
171 	if (eclockfreq == 0)
172 		eclockfreq = 715909;	/* guess NTSC */
173 
174 #ifdef DRACO
175 	if (dracorev >= 4) {
176 		if (amiga_clk_interval == 0)	/* Only do this 1st time */
177 			eclockfreq /= 7;
178 		clockchip = "QuickLogic";
179 	} else if (dracorev) {
180 		clockcia = (struct CIA *)CIAAbase;
181 		clockchip = "CIA A";
182 	} else
183 #endif
184 	{
185 		clockcia = (struct CIA *)CIABbase;
186 		clockchip = "CIA B";
187 	}
188 
189 	amiga_clk_interval = (eclockfreq / hz);
190 
191 	clk_timecounter.tc_name = clockchip;
192 	clk_timecounter.tc_frequency = eclockfreq;
193 
194 	fast_delay_limit = UINT_MAX / amiga_clk_interval;
195 
196 	if (dp != NULL) {	/* real autoconfig? */
197 		printf(": %s system hz %d hardware hz %d\n", clockchip, hz,
198 		    eclockfreq);
199 		tc_init(&clk_timecounter);
200 	}
201 
202 #ifdef DRACO
203 	if (dracorev >= 4) {
204 		/*
205 		 * can't preload anything beforehand, timer is free_running;
206 		 * but need this for delay calibration.
207 		 */
208 
209 		draco_ioct->io_timerlo = amiga_clk_interval & 0xff;
210 		draco_ioct->io_timerhi = amiga_clk_interval >> 8;
211 
212 		return;
213 	}
214 #endif
215 	/*
216 	 * stop timer A
217 	 */
218 	clockcia->cra = clockcia->cra & 0xc0;
219 	clockcia->icr = 1 << 0;		/* disable timer A interrupt */
220 	interval = clockcia->icr;		/* and make sure it's clear */
221 
222 	/*
223 	 * load interval into registers.
224          * the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz
225 	 * supprort for PAL WHEN?!?! XXX
226 	 */
227 	interval = amiga_clk_interval - 1;
228 
229 	/*
230 	 * order of setting is important !
231 	 */
232 	clockcia->talo = interval & 0xff;
233 	clockcia->tahi = interval >> 8;
234 	/*
235 	 * start timer A in continuous mode
236 	 */
237 	clockcia->cra = (clockcia->cra & 0xc0) | 1;
238 }
239 
240 void
241 cpu_initclocks(void)
242 {
243 #ifdef DRACO
244 	unsigned char dracorev;
245 	dracorev = is_draco();
246 	if (dracorev >= 4) {
247 		draco_ioct->io_timerlo = amiga_clk_interval & 0xFF;
248 		draco_ioct->io_timerhi = amiga_clk_interval >> 8;
249 		draco_ioct->io_timerrst = 0;	/* any value resets */
250 		single_inst_bset_b(draco_ioct->io_status2, DRSTAT2_TMRINTENA);
251 
252 		return;
253 	}
254 #endif
255 	/*
256 	 * enable interrupts for timer A
257 	 */
258 	clockcia->icr = (1<<7) | (1<<0);
259 
260 	/*
261 	 * start timer A in continuous shot mode
262 	 */
263 	clockcia->cra = (clockcia->cra & 0xc0) | 1;
264 
265 	/*
266 	 * and globally enable interrupts for ciab
267 	 */
268 #ifdef DRACO
269 	if (dracorev)		/* we use cia a on DraCo */
270 		single_inst_bset_b(*draco_intena, DRIRQ_INT2);
271 	else
272 #endif
273 		custom.intena = INTF_SETCLR | INTF_EXTER;
274 
275 }
276 
277 void
278 setstatclockrate(int hertz)
279 {
280 }
281 
282 /*
283  * Returns ticks  since last recorded clock "tick"
284  * (i.e. clock interrupt).
285  */
286 static u_int
287 clk_gettick(void)
288 {
289 	u_int interval;
290 	u_char hi, hi2, lo;
291 
292 #ifdef DRACO
293 	if (is_draco() >= 4) {
294 		hi2 = draco_ioct->io_chiprev;	/* latch timer */
295 		hi = draco_ioct->io_timerhi;
296 		lo = draco_ioct->io_timerlo;
297 		interval = ((hi<<8) | lo);
298 		if (interval > amiga_clk_interval)	/* timer underflow */
299 			interval = 65536 + amiga_clk_interval - interval;
300 		else
301 			interval = amiga_clk_interval - interval;
302 
303 	} else
304 #endif
305 	{
306 		hi  = clockcia->tahi;
307 		lo  = clockcia->talo;
308 		hi2 = clockcia->tahi;
309 		if (hi != hi2) {
310 			lo = clockcia->talo;
311 			hi = hi2;
312 		}
313 
314 		interval = (amiga_clk_interval - 1) - ((hi<<8) | lo);
315 
316 		/*
317 		 * should read ICR and if there's an int pending, adjust
318 		 * interval. However, since reading ICR clears the interrupt,
319 		 * we'd lose a hardclock int, and this is not tolerable.
320 		 */
321 	}
322 
323 	return interval;
324 }
325 
326 static u_int
327 clk_getcounter(struct timecounter *tc)
328 {
329 	static int last_hardclock_ticks;
330 	static u_int last_clock_tick = 0;
331 	int old_hardclock_ticks;
332 	u_int clock_tick;
333 
334 	do {
335 		old_hardclock_ticks = hardclock_ticks;
336 		clock_tick = clk_gettick();
337 	} while (old_hardclock_ticks != hardclock_ticks);
338 
339 	/*
340 	 * Handle the situation of a wrapped interval counter, while
341 	 * the hardclock() interrupt was not yet executed to update
342 	 * hardclock_ticks.
343 	 */
344 	if (last_hardclock_ticks > old_hardclock_ticks)
345 		old_hardclock_ticks = last_hardclock_ticks;
346 	if (clock_tick < last_clock_tick &&
347 	    old_hardclock_ticks == last_hardclock_ticks)
348 		old_hardclock_ticks++;
349 	last_hardclock_ticks = old_hardclock_ticks;
350 	last_clock_tick = clock_tick;
351 
352 	return old_hardclock_ticks * amiga_clk_interval + clock_tick;
353 }
354 
355 #if notyet
356 
357 /* implement this later. I'd suggest using both timers in CIA-A, they're
358    not yet used. */
359 
360 #include "clock.h"
361 #if NCLOCK > 0
362 /*
363  * /dev/clock: mappable high resolution timer.
364  *
365  * This code implements a 32-bit recycling counter (with a 4 usec period)
366  * using timers 2 & 3 on the 6840 clock chip.  The counter can be mapped
367  * RO into a user's address space to achieve low overhead (no system calls),
368  * high-precision timing.
369  *
370  * Note that timer 3 is also used for the high precision profiling timer
371  * (PROFTIMER code above).  Care should be taken when both uses are
372  * configured as only a token effort is made to avoid conflicting use.
373  */
374 #include <sys/proc.h>
375 #include <sys/resourcevar.h>
376 #include <sys/ioctl.h>
377 #include <sys/malloc.h>
378 #include <uvm/uvm_extern.h>
379 #include <amiga/amiga/clockioctl.h>
380 #include <sys/specdev.h>
381 #include <sys/vnode.h>
382 #include <sys/mman.h>
383 
384 int clockon = 0;		/* non-zero if high-res timer enabled */
385 #ifdef PROFTIMER
386 int  profprocs = 0;		/* # of procs using profiling timer */
387 #endif
388 #ifdef DEBUG
389 int clockdebug = 0;
390 #endif
391 
392 /*ARGSUSED*/
393 int
394 clockopen(dev_t dev, int flags)
395 {
396 #ifdef PROFTIMER
397 #ifdef PROF
398 	/*
399 	 * Kernel profiling enabled, give up.
400 	 */
401 	if (profiling)
402 		return(EBUSY);
403 #endif
404 	/*
405 	 * If any user processes are profiling, give up.
406 	 */
407 	if (profprocs)
408 		return(EBUSY);
409 #endif
410 	if (!clockon) {
411 		startclock();
412 		clockon++;
413 	}
414 	return(0);
415 }
416 
417 /*ARGSUSED*/
418 int
419 clockclose(dev_t dev, int flags)
420 {
421 	(void) clockunmmap(dev, (void *)0, curproc);	/* XXX */
422 	stopclock();
423 	clockon = 0;
424 	return(0);
425 }
426 
427 /*ARGSUSED*/
428 int
429 clockioctl(dev_t dev, u_long cmd, void *data, int flag, struct proc *p)
430 {
431 	int error = 0;
432 
433 	switch (cmd) {
434 
435 	case CLOCKMAP:
436 		error = clockmmap(dev, (void **)data, p);
437 		break;
438 
439 	case CLOCKUNMAP:
440 		error = clockunmmap(dev, *(void **)data, p);
441 		break;
442 
443 	case CLOCKGETRES:
444 		*(int *)data = CLK_RESOLUTION;
445 		break;
446 
447 	default:
448 		error = EINVAL;
449 		break;
450 	}
451 	return(error);
452 }
453 
454 /*ARGSUSED*/
455 void
456 clockmap(dev_t dev, int off, int prot)
457 {
458 	return((off + (INTIOBASE+CLKBASE+CLKSR-1)) >> PGSHIFT);
459 }
460 
461 int
462 clockmmap(dev_t dev, void **addrp, struct proc *p)
463 {
464 	int error;
465 	struct vnode vn;
466 	struct specinfo si;
467 	int flags;
468 
469 	flags = MAP_FILE|MAP_SHARED;
470 	if (*addrp)
471 		flags |= MAP_FIXED;
472 	else
473 		*addrp = (void *)0x1000000;	/* XXX */
474 	vn.v_type = VCHR;			/* XXX */
475 	vn.v_specinfo = &si;			/* XXX */
476 	vn.v_rdev = dev;			/* XXX */
477 	error = vm_mmap(&p->p_vmspace->vm_map, (vm_offset_t *)addrp,
478 			PAGE_SIZE, VM_PROT_ALL, flags, (void *)&vn, 0);
479 	return(error);
480 }
481 
482 int
483 clockunmmap(dev_t dev, void *addr, struct proc *p)
484 {
485 	int rv;
486 
487 	if (addr == 0)
488 		return(EINVAL);		/* XXX: how do we deal with this? */
489 	uvm_deallocate(p->p_vmspace->vm_map, (vm_offset_t)addr, PAGE_SIZE);
490 	return 0;
491 }
492 
493 void
494 startclock(void)
495 {
496 	register struct clkreg *clk = (struct clkreg *)clkstd[0];
497 
498 	clk->clk_msb2 = -1; clk->clk_lsb2 = -1;
499 	clk->clk_msb3 = -1; clk->clk_lsb3 = -1;
500 
501 	clk->clk_cr2 = CLK_CR3;
502 	clk->clk_cr3 = CLK_OENAB|CLK_8BIT;
503 	clk->clk_cr2 = CLK_CR1;
504 	clk->clk_cr1 = CLK_IENAB;
505 }
506 
507 void
508 stopclock(void)
509 {
510 	register struct clkreg *clk = (struct clkreg *)clkstd[0];
511 
512 	clk->clk_cr2 = CLK_CR3;
513 	clk->clk_cr3 = 0;
514 	clk->clk_cr2 = CLK_CR1;
515 	clk->clk_cr1 = CLK_IENAB;
516 }
517 #endif
518 
519 #endif
520 
521 
522 #ifdef PROFTIMER
523 /*
524  * This code allows the amiga kernel to use one of the extra timers on
525  * the clock chip for profiling, instead of the regular system timer.
526  * The advantage of this is that the profiling timer can be turned up to
527  * a higher interrupt rate, giving finer resolution timing. The profclock
528  * routine is called from the lev6intr in locore, and is a specialized
529  * routine that calls addupc. The overhead then is far less than if
530  * hardclock/softclock was called. Further, the context switch code in
531  * locore has been changed to turn the profile clock on/off when switching
532  * into/out of a process that is profiling (startprofclock/stopprofclock).
533  * This reduces the impact of the profiling clock on other users, and might
534  * possibly increase the accuracy of the profiling.
535  */
536 int  profint   = PRF_INTERVAL;	/* Clock ticks between interrupts */
537 int  profscale = 0;		/* Scale factor from sys clock to prof clock */
538 char profon    = 0;		/* Is profiling clock on? */
539 
540 /* profon values - do not change, locore.s assumes these values */
541 #define PRF_NONE	0x00
542 #define	PRF_USER	0x01
543 #define	PRF_KERNEL	0x80
544 
545 void
546 initprofclock(void)
547 {
548 #if NCLOCK > 0
549 	struct proc *p = curproc;		/* XXX */
550 
551 	/*
552 	 * If the high-res timer is running, force profiling off.
553 	 * Unfortunately, this gets reflected back to the user not as
554 	 * an error but as a lack of results.
555 	 */
556 	if (clockon) {
557 		p->p_stats->p_prof.pr_scale = 0;
558 		return;
559 	}
560 	/*
561 	 * Keep track of the number of user processes that are profiling
562 	 * by checking the scale value.
563 	 *
564 	 * XXX: this all assumes that the profiling code is well behaved;
565 	 * i.e. profil() is called once per process with pcscale non-zero
566 	 * to turn it on, and once with pcscale zero to turn it off.
567 	 * Also assumes you don't do any forks or execs.  Oh well, there
568 	 * is always adb...
569 	 */
570 	if (p->p_stats->p_prof.pr_scale)
571 		profprocs++;
572 	else
573 		profprocs--;
574 #endif
575 	/*
576 	 * The profile interrupt interval must be an even divisor
577 	 * of the amiga_clk_interval so that scaling from a system clock
578 	 * tick to a profile clock tick is possible using integer math.
579 	 */
580 	if (profint > amiga_clk_interval || (amiga_clk_interval % profint) != 0)
581 		profint = amiga_clk_interval;
582 	profscale = amiga_clk_interval / profint;
583 }
584 
585 void
586 startprofclock(void)
587 {
588   unsigned short interval;
589 
590   /* stop timer B */
591   clockcia->crb = clockcia->crb & 0xc0;
592 
593   /* load interval into registers.
594      the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz */
595 
596   interval = profint - 1;
597 
598   /* order of setting is important ! */
599   clockcia->tblo = interval & 0xff;
600   clockcia->tbhi = interval >> 8;
601 
602   /* enable interrupts for timer B */
603   clockcia->icr = (1<<7) | (1<<1);
604 
605   /* start timer B in continuous shot mode */
606   clockcia->crb = (clockcia->crb & 0xc0) | 1;
607 }
608 
609 void
610 stopprofclock(void)
611 {
612   /* stop timer B */
613   clockcia->crb = clockcia->crb & 0xc0;
614 }
615 
616 #ifdef PROF
617 /*
618  * profclock() is expanded in line in lev6intr() unless profiling kernel.
619  * Assumes it is called with clock interrupts blocked.
620  */
621 void
622 profclock(void *pc, int ps)
623 {
624 	/*
625 	 * Came from user mode.
626 	 * If this process is being profiled record the tick.
627 	 */
628 	if (USERMODE(ps)) {
629 		if (p->p_stats.p_prof.pr_scale)
630 			addupc(pc, &curproc->p_stats.p_prof, 1);
631 	}
632 	/*
633 	 * Came from kernel (supervisor) mode.
634 	 * If we are profiling the kernel, record the tick.
635 	 */
636 	else if (profiling < 2) {
637 		register int s = pc - s_lowpc;
638 
639 		if (s < s_textsize)
640 			kcount[s / (HISTFRACTION * sizeof (*kcount))]++;
641 	}
642 	/*
643 	 * Kernel profiling was on but has been disabled.
644 	 * Mark as no longer profiling kernel and if all profiling done,
645 	 * disable the clock.
646 	 */
647 	if (profiling && (profon & PRF_KERNEL)) {
648 		profon &= ~PRF_KERNEL;
649 		if (profon == PRF_NONE)
650 			stopprofclock();
651 	}
652 }
653 #endif
654 #endif
655 
656 void
657 delay(unsigned int n)
658 {
659 	unsigned int cur_tick, initial_tick;
660 	int remaining;
661 
662 	/*
663 	 * Read the counter first, so that the rest of the setup overhead is
664 	 * counted.
665 	 */
666 	initial_tick = clk_gettick();
667 
668 	if (amiga_clk_interval == 0) {
669 		/*
670 		 * Clock is not initialised yet,
671 		 * so just do some ad-hoc loop.
672 		 */
673 		static uint32_t dummy;
674 
675 		n *= 4;
676 		while (n--)
677 			dummy *= eclockfreq;
678 		return;
679 	}
680 
681 	if (n <= fast_delay_limit) {
682 		/*
683 		 * For unsigned arithmetic, division can be replaced with
684 		 * multiplication with the inverse and a shift.
685 		 */
686 		remaining = n * eclockfreq / 1000000;
687 	} else {
688 		/* This is a very long delay.
689 		 * Being slow here doesn't matter.
690 		 */
691 		remaining = (unsigned long long) n * eclockfreq / 1000000;
692 	}
693 
694 	while (remaining > 0) {
695 		cur_tick = clk_gettick();
696 		if (cur_tick > initial_tick)
697 			remaining -= amiga_clk_interval - (cur_tick - initial_tick);
698 		else
699 			remaining -= initial_tick - cur_tick;
700 		initial_tick = cur_tick;
701 	}
702 }
703