xref: /netbsd-src/sys/arch/amiga/dev/clock.c (revision b1c86f5f087524e68db12794ee9c3e3da1ab17a0)
1 /*	$NetBSD: clock.c,v 1.51 2009/12/12 13:10:36 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 1.51 2009/12/12 13:10:36 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 /*
104  * Machine-dependent clock routines.
105  *
106  * Startrtclock restarts the real-time clock, which provides
107  * hardclock interrupts to kern_clock.c.
108  *
109  * Inittodr initializes the time of day hardware which provides
110  * date functions.
111  *
112  * Resettodr restores the time of day hardware after a time change.
113  *
114  * A note on the real-time clock:
115  * We actually load the clock with amiga_clk_interval-1 instead of amiga_clk_interval.
116  * This is because the counter decrements to zero after N+1 enabled clock
117  * periods where N is the value loaded into the counter.
118  */
119 
120 int clockmatch(struct device *, struct cfdata *, void *);
121 void clockattach(struct device *, struct device *, void *);
122 void cpu_initclocks(void);
123 static void calibrate_delay(struct device *);
124 
125 /* the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz.
126    We're using a 100 Hz clock. */
127 int amiga_clk_interval;
128 int eclockfreq;
129 struct CIA *clockcia;
130 
131 static u_int clk_getcounter(struct timecounter *);
132 
133 static struct timecounter clk_timecounter = {
134 	clk_getcounter,	/* get_timecount */
135 	0,		/* no poll_pps */
136 	~0u,		/* counter_mask */
137 	0,		/* frequency */
138 	"clock",	/* name, overriden later */
139 	100,		/* quality */
140 	NULL,		/* prev */
141 	NULL,		/* next */
142 };
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 	int chipfreq;
164 #ifdef DRACO
165 	u_char dracorev;
166 #endif
167 
168 	if (eclockfreq == 0)
169 		eclockfreq = 715909;	/* guess NTSC */
170 
171 	chipfreq = eclockfreq;
172 
173 #ifdef DRACO
174 	dracorev = is_draco();
175 	if (dracorev >= 4) {
176 		chipfreq = eclockfreq / 7;
177 		clockchip = "QuickLogic";
178 	} else if (dracorev) {
179 		clockcia = (struct CIA *)CIAAbase;
180 		clockchip = "CIA A";
181 	} else
182 #endif
183 	{
184 		clockcia = (struct CIA *)CIABbase;
185 		clockchip = "CIA B";
186 	}
187 
188 	amiga_clk_interval = chipfreq / hz;
189 
190 	if (dp != NULL) {	/* real autoconfig? */
191 		printf(": %s system hz %d hardware hz %d\n", clockchip, hz,
192 		    chipfreq);
193 
194 		clk_timecounter.tc_name = clockchip;
195 		clk_timecounter.tc_frequency = chipfreq;
196 		tc_init(&clk_timecounter);
197 	}
198 
199 #ifdef DRACO
200 	if (dracorev >= 4) {
201 		/*
202 		 * can't preload anything beforehand, timer is free_running;
203 		 * but need this for delay calibration.
204 		 */
205 
206 		draco_ioct->io_timerlo = amiga_clk_interval & 0xff;
207 		draco_ioct->io_timerhi = amiga_clk_interval >> 8;
208 
209 		calibrate_delay(dp);
210 
211 		return;
212 	}
213 #endif
214 	/*
215 	 * stop timer A
216 	 */
217 	clockcia->cra = clockcia->cra & 0xc0;
218 	clockcia->icr = 1 << 0;		/* disable timer A interrupt */
219 	interval = clockcia->icr;		/* and make sure it's clear */
220 
221 	/*
222 	 * load interval into registers.
223          * the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz
224 	 */
225 	interval = amiga_clk_interval - 1;
226 
227 	/*
228 	 * order of setting is important !
229 	 */
230 	clockcia->talo = interval & 0xff;
231 	clockcia->tahi = interval >> 8;
232 	/*
233 	 * start timer A in continuous mode
234 	 */
235 	clockcia->cra = (clockcia->cra & 0xc0) | 1;
236 
237 	calibrate_delay(dp);
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 prev_hardclock;
330 	static u_int prev_counter;
331 	int cur_hardclock;
332 	u_int counter;
333 
334 	do {
335 		cur_hardclock = hardclock_ticks;
336 		counter = clk_gettick();
337 	} while (cur_hardclock != 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 (cur_hardclock < prev_hardclock)
345 		cur_hardclock = prev_hardclock;
346 	if (counter < prev_counter && cur_hardclock == prev_hardclock)
347 		cur_hardclock++;
348 
349 	prev_hardclock = cur_hardclock;
350 	prev_counter = counter;
351 
352 	return cur_hardclock * amiga_clk_interval + counter;
353 }
354 
355 /*
356  * Calibrate delay loop.
357  * We use two iterations because we don't have enough bits to do a factor of
358  * 8 with better than 1%.
359  *
360  * XXX Note that we MUST stay below 1 tick if using clk_gettick(), even for
361  * underestimated values of delaydivisor.
362  *
363  * XXX the "ns" below is only correct for a shift of 10 bits, and even then
364  * off by 2.4%
365  */
366 static void
367 calibrate_delay(struct device *dp)
368 {
369 	unsigned long t1, t2;
370 	extern u_int32_t delaydivisor;
371 		/* XXX this should be defined elsewhere */
372 
373 	if (dp)
374 		printf("Calibrating delay loop... ");
375 
376 	do {
377 		t1 = clk_gettick();
378 		delay(1024);
379 		t2 = clk_gettick();
380 	} while (t2 <= t1);
381 	t2 = ((t2 - t1) * 1000000) / (amiga_clk_interval * hz);
382 	delaydivisor = (delaydivisor * t2 + 1023) >> 10;
383 #ifdef DEBUG
384 	if (dp)
385 		printf("\ndiff %ld us, new divisor %u/1024 us\n", t2,
386 		    delaydivisor);
387 	do {
388 		t1 = clk_gettick();
389 		delay(1024);
390 		t2 = clk_gettick();
391 	} while (t2 <= t1);
392 	t2 = ((t2 - t1) * 1000000) / (amiga_clk_interval * hz);
393 	delaydivisor = (delaydivisor * t2 + 1023) >> 10;
394 	if (dp)
395 		printf("diff %ld us, new divisor %u/1024 us\n", t2,
396 		    delaydivisor);
397 #endif
398 	do {
399 		t1 = clk_gettick();
400 		delay(1024);
401 		t2 = clk_gettick();
402 	} while (t2 <= t1);
403 	t2 = ((t2 - t1) * 1000000) / (amiga_clk_interval * hz);
404 	delaydivisor = (delaydivisor * t2 + 1023) >> 10;
405 #ifdef DEBUG
406 	if (dp)
407 		printf("diff %ld us, new divisor ", t2);
408 #endif
409 	if (dp)
410 		printf("%u/1024 us\n", delaydivisor);
411 }
412 
413 #if notyet
414 
415 /* implement this later. I'd suggest using both timers in CIA-A, they're
416    not yet used. */
417 
418 #include "clock.h"
419 #if NCLOCK > 0
420 /*
421  * /dev/clock: mappable high resolution timer.
422  *
423  * This code implements a 32-bit recycling counter (with a 4 usec period)
424  * using timers 2 & 3 on the 6840 clock chip.  The counter can be mapped
425  * RO into a user's address space to achieve low overhead (no system calls),
426  * high-precision timing.
427  *
428  * Note that timer 3 is also used for the high precision profiling timer
429  * (PROFTIMER code above).  Care should be taken when both uses are
430  * configured as only a token effort is made to avoid conflicting use.
431  */
432 #include <sys/proc.h>
433 #include <sys/resourcevar.h>
434 #include <sys/ioctl.h>
435 #include <sys/malloc.h>
436 #include <uvm/uvm_extern.h>
437 #include <amiga/amiga/clockioctl.h>
438 #include <sys/specdev.h>
439 #include <sys/vnode.h>
440 #include <sys/mman.h>
441 
442 int clockon = 0;		/* non-zero if high-res timer enabled */
443 #ifdef PROFTIMER
444 int  profprocs = 0;		/* # of procs using profiling timer */
445 #endif
446 #ifdef DEBUG
447 int clockdebug = 0;
448 #endif
449 
450 /*ARGSUSED*/
451 int
452 clockopen(dev_t dev, int flags)
453 {
454 #ifdef PROFTIMER
455 #ifdef PROF
456 	/*
457 	 * Kernel profiling enabled, give up.
458 	 */
459 	if (profiling)
460 		return(EBUSY);
461 #endif
462 	/*
463 	 * If any user processes are profiling, give up.
464 	 */
465 	if (profprocs)
466 		return(EBUSY);
467 #endif
468 	if (!clockon) {
469 		startclock();
470 		clockon++;
471 	}
472 	return(0);
473 }
474 
475 /*ARGSUSED*/
476 int
477 clockclose(dev_t dev, int flags)
478 {
479 	(void) clockunmmap(dev, (void *)0, curproc);	/* XXX */
480 	stopclock();
481 	clockon = 0;
482 	return(0);
483 }
484 
485 /*ARGSUSED*/
486 int
487 clockioctl(dev_t dev, u_long cmd, void *data, int flag, struct proc *p)
488 {
489 	int error = 0;
490 
491 	switch (cmd) {
492 
493 	case CLOCKMAP:
494 		error = clockmmap(dev, (void **)data, p);
495 		break;
496 
497 	case CLOCKUNMAP:
498 		error = clockunmmap(dev, *(void **)data, p);
499 		break;
500 
501 	case CLOCKGETRES:
502 		*(int *)data = CLK_RESOLUTION;
503 		break;
504 
505 	default:
506 		error = EINVAL;
507 		break;
508 	}
509 	return(error);
510 }
511 
512 /*ARGSUSED*/
513 void
514 clockmap(dev_t dev, int off, int prot)
515 {
516 	return((off + (INTIOBASE+CLKBASE+CLKSR-1)) >> PGSHIFT);
517 }
518 
519 int
520 clockmmap(dev_t dev, void **addrp, struct proc *p)
521 {
522 	int error;
523 	struct vnode vn;
524 	struct specinfo si;
525 	int flags;
526 
527 	flags = MAP_FILE|MAP_SHARED;
528 	if (*addrp)
529 		flags |= MAP_FIXED;
530 	else
531 		*addrp = (void *)0x1000000;	/* XXX */
532 	vn.v_type = VCHR;			/* XXX */
533 	vn.v_specinfo = &si;			/* XXX */
534 	vn.v_rdev = dev;			/* XXX */
535 	error = vm_mmap(&p->p_vmspace->vm_map, (vm_offset_t *)addrp,
536 			PAGE_SIZE, VM_PROT_ALL, flags, (void *)&vn, 0);
537 	return(error);
538 }
539 
540 int
541 clockunmmap(dev_t dev, void *addr, struct proc *p)
542 {
543 	int rv;
544 
545 	if (addr == 0)
546 		return(EINVAL);		/* XXX: how do we deal with this? */
547 	uvm_deallocate(p->p_vmspace->vm_map, (vm_offset_t)addr, PAGE_SIZE);
548 	return 0;
549 }
550 
551 void
552 startclock(void)
553 {
554 	register struct clkreg *clk = (struct clkreg *)clkstd[0];
555 
556 	clk->clk_msb2 = -1; clk->clk_lsb2 = -1;
557 	clk->clk_msb3 = -1; clk->clk_lsb3 = -1;
558 
559 	clk->clk_cr2 = CLK_CR3;
560 	clk->clk_cr3 = CLK_OENAB|CLK_8BIT;
561 	clk->clk_cr2 = CLK_CR1;
562 	clk->clk_cr1 = CLK_IENAB;
563 }
564 
565 void
566 stopclock(void)
567 {
568 	register struct clkreg *clk = (struct clkreg *)clkstd[0];
569 
570 	clk->clk_cr2 = CLK_CR3;
571 	clk->clk_cr3 = 0;
572 	clk->clk_cr2 = CLK_CR1;
573 	clk->clk_cr1 = CLK_IENAB;
574 }
575 #endif
576 
577 #endif
578 
579 
580 #ifdef PROFTIMER
581 /*
582  * This code allows the amiga kernel to use one of the extra timers on
583  * the clock chip for profiling, instead of the regular system timer.
584  * The advantage of this is that the profiling timer can be turned up to
585  * a higher interrupt rate, giving finer resolution timing. The profclock
586  * routine is called from the lev6intr in locore, and is a specialized
587  * routine that calls addupc. The overhead then is far less than if
588  * hardclock/softclock was called. Further, the context switch code in
589  * locore has been changed to turn the profile clock on/off when switching
590  * into/out of a process that is profiling (startprofclock/stopprofclock).
591  * This reduces the impact of the profiling clock on other users, and might
592  * possibly increase the accuracy of the profiling.
593  */
594 int  profint   = PRF_INTERVAL;	/* Clock ticks between interrupts */
595 int  profscale = 0;		/* Scale factor from sys clock to prof clock */
596 char profon    = 0;		/* Is profiling clock on? */
597 
598 /* profon values - do not change, locore.s assumes these values */
599 #define PRF_NONE	0x00
600 #define	PRF_USER	0x01
601 #define	PRF_KERNEL	0x80
602 
603 void
604 initprofclock(void)
605 {
606 #if NCLOCK > 0
607 	struct proc *p = curproc;		/* XXX */
608 
609 	/*
610 	 * If the high-res timer is running, force profiling off.
611 	 * Unfortunately, this gets reflected back to the user not as
612 	 * an error but as a lack of results.
613 	 */
614 	if (clockon) {
615 		p->p_stats->p_prof.pr_scale = 0;
616 		return;
617 	}
618 	/*
619 	 * Keep track of the number of user processes that are profiling
620 	 * by checking the scale value.
621 	 *
622 	 * XXX: this all assumes that the profiling code is well behaved;
623 	 * i.e. profil() is called once per process with pcscale non-zero
624 	 * to turn it on, and once with pcscale zero to turn it off.
625 	 * Also assumes you don't do any forks or execs.  Oh well, there
626 	 * is always adb...
627 	 */
628 	if (p->p_stats->p_prof.pr_scale)
629 		profprocs++;
630 	else
631 		profprocs--;
632 #endif
633 	/*
634 	 * The profile interrupt interval must be an even divisor
635 	 * of the amiga_clk_interval so that scaling from a system clock
636 	 * tick to a profile clock tick is possible using integer math.
637 	 */
638 	if (profint > amiga_clk_interval || (amiga_clk_interval % profint) != 0)
639 		profint = amiga_clk_interval;
640 	profscale = amiga_clk_interval / profint;
641 }
642 
643 void
644 startprofclock(void)
645 {
646   unsigned short interval;
647 
648   /* stop timer B */
649   clockcia->crb = clockcia->crb & 0xc0;
650 
651   /* load interval into registers.
652      the clocks run at NTSC: 715.909kHz or PAL: 709.379kHz */
653 
654   interval = profint - 1;
655 
656   /* order of setting is important ! */
657   clockcia->tblo = interval & 0xff;
658   clockcia->tbhi = interval >> 8;
659 
660   /* enable interrupts for timer B */
661   clockcia->icr = (1<<7) | (1<<1);
662 
663   /* start timer B in continuous shot mode */
664   clockcia->crb = (clockcia->crb & 0xc0) | 1;
665 }
666 
667 void
668 stopprofclock(void)
669 {
670   /* stop timer B */
671   clockcia->crb = clockcia->crb & 0xc0;
672 }
673 
674 #ifdef PROF
675 /*
676  * profclock() is expanded in line in lev6intr() unless profiling kernel.
677  * Assumes it is called with clock interrupts blocked.
678  */
679 void
680 profclock(void *pc, int ps)
681 {
682 	/*
683 	 * Came from user mode.
684 	 * If this process is being profiled record the tick.
685 	 */
686 	if (USERMODE(ps)) {
687 		if (p->p_stats.p_prof.pr_scale)
688 			addupc(pc, &curproc->p_stats.p_prof, 1);
689 	}
690 	/*
691 	 * Came from kernel (supervisor) mode.
692 	 * If we are profiling the kernel, record the tick.
693 	 */
694 	else if (profiling < 2) {
695 		register int s = pc - s_lowpc;
696 
697 		if (s < s_textsize)
698 			kcount[s / (HISTFRACTION * sizeof (*kcount))]++;
699 	}
700 	/*
701 	 * Kernel profiling was on but has been disabled.
702 	 * Mark as no longer profiling kernel and if all profiling done,
703 	 * disable the clock.
704 	 */
705 	if (profiling && (profon & PRF_KERNEL)) {
706 		profon &= ~PRF_KERNEL;
707 		if (profon == PRF_NONE)
708 			stopprofclock();
709 	}
710 }
711 #endif
712 #endif
713