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clock.c revision 1.2 
      1 /*	$NetBSD: clock.c,v 1.2 1998/01/19 03:00:59 sakamoto Exp $	*/
      2 
      3 /*
      4  * Copyright (C) 1995, 1996 Wolfgang Solfrank.
      5  * Copyright (C) 1995, 1996 TooLs GmbH.
      6  * All rights reserved.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by TooLs GmbH.
     19  * 4. The name of TooLs GmbH may not be used to endorse or promote products
     20  *    derived from this software without specific prior written permission.
     21  *
     22  * THIS SOFTWARE IS PROVIDED BY TOOLS GMBH ``AS IS'' AND ANY EXPRESS OR
     23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     25  * IN NO EVENT SHALL TOOLS GMBH BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     26  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     27  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     28  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     29  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     30  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     31  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     32  */
     33 
     34 #include <sys/param.h>
     35 #include <dev/isa/isareg.h>
     36 #include <dev/ic/i8253reg.h>
     37 
     38 #define FIRST_GUESS	0x2000
     39 
     40 static u_long ns_per_tick;
     41 
     42 static inline u_quad_t
     43 mftb()
     44 {
     45 	u_long scratch;
     46 	u_quad_t tb;
     47 
     48 	asm ("1: mftbu %0; mftb %0+1; mftbu %1; cmpw %0,%1; bne 1b"
     49 	    : "=r"(tb), "=r"(scratch));
     50 	return tb;
     51 }
     52 
     53 /*
     54  * Wait for about n microseconds (at least!).
     55  */
     56 void
     57 delay(n)
     58 	int n;
     59 {
     60 	u_quad_t tb;
     61 	u_long tbh, tbl, scratch;
     62 
     63 	tb = mftb();
     64 	tb += (n * 1000 + ns_per_tick - 1) / ns_per_tick;
     65 	tbh = tb >> 32;
     66 	tbl = tb;
     67 	asm ("1: mftbu %0; cmpw %0,%1; blt 1b; bgt 2f; mftb %0; cmpw %0,%2; blt 1b; 2:"
     68 	     :: "r"(scratch), "r"(tbh), "r"(tbl));
     69 }
     70 
     71 int
     72 findcpuspeed()
     73 {
     74 	int i;
     75 	int ticks_per_sec;
     76 	u_short remainder;
     77 	u_quad_t tstart, tend;
     78 
     79 	/* Put counter in count down mode */
     80 	outb(TIMER_MODE, TIMER_SEL0|TIMER_16BIT|TIMER_RATEGEN);
     81 	outb(TIMER_CNTR0, 0xff);	/* lo */
     82 	outb(TIMER_CNTR0, 0xff);	/* hi */
     83 	for (i = FIRST_GUESS; i; i--)
     84 		;
     85 	/* Read the value left in the counter */
     86 	outb(TIMER_MODE, TIMER_SEL0|TIMER_LATCH);
     87 	remainder = inb(TIMER_CNTR0);
     88 	remainder += (inb(TIMER_CNTR0) << 8);
     89 
     90 	tstart = mftb();
     91 	for (i = FIRST_GUESS; i; i--)
     92 		;
     93 	tend = mftb();
     94 	if (tend > tstart)
     95 		tend -= tstart;
     96 	else
     97 		tend += UQUAD_MAX - tstart;
     98 
     99 	ticks_per_sec = (int)(tend * TIMER_FREQ / (0xffff - remainder));
    100 	if (ticks_per_sec > 8000000)		/* XXX */
    101 		ticks_per_sec = 33000000 / 4;
    102 	else
    103 		ticks_per_sec = 25000000 / 4;
    104 	ns_per_tick = 1000000000 / ticks_per_sec;
    105 
    106 	return (ticks_per_sec);
    107 }
    108