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/* $Id: udelay.c,v 1.3 2001/03/01 22:33:50 reinelt Exp $
*
* short delays
*
* Copyright 1999, 2000 by Michael Reinelt (reinelt@eunet.at)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*
* $Log: udelay.c,v $
* Revision 1.3 2001/03/01 22:33:50 reinelt
*
* renamed Raster_flush() to PPM_flush()
*
* Revision 1.2 2000/07/31 10:43:44 reinelt
*
* some changes to support kernel-2.4 (different layout of various files in /proc)
*
* Revision 1.1 2000/04/15 16:56:52 reinelt
*
* moved delay loops to udelay.c
* renamed -d (debugging) switch to -v (verbose)
* new switch -d to calibrate delay loop
* 'Delay' entry for HD44780 back again
* delay loops will not calibrate automatically, because this will fail with hich CPU load
*
*/
/*
*
* exported fuctions:
*
* void udelay (unsigned long usec)
* delays program execution for usec microseconds
* uses global variable 'loops_per_usec', which has to be set before.
* This function does busy-waiting! so use only for delays smaller
* than 10 msec
*
* void udelay_calibrate (void)
* does a binary approximation for 'loops_per_usec'
* should be called several times on an otherwise idle machine
* the maximum value should be used
*
*/
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include "udelay.h"
unsigned long loops_per_usec;
void udelay (unsigned long usec)
{
unsigned long loop=usec*loops_per_usec;
__asm__ (".align 16\n"
"1:\tdecl %0\n"
"\tjne 1b"
: /* no result */
:"a" (loop));
}
/* adopted from /usr/src/linux/init/main.c */
void udelay_calibrate (void)
{
clock_t tick;
unsigned long bit;
loops_per_usec=1;
while (loops_per_usec<<=1) {
tick=clock();
while (clock()==tick);
tick=clock();
udelay(1000000/CLK_TCK);
if (clock()>tick)
break;
}
loops_per_usec>>=1;
bit=loops_per_usec;
while (bit>>=1) {
loops_per_usec|=bit;
tick=clock();
while (clock()==tick);
tick=clock();
udelay(1000000/CLK_TCK);
if (clock()>tick)
loops_per_usec&=~bit;
}
}
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