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https://github.com/netfun2000/lcd4linux.git
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7ff246c045
some changes to support kernel-2.4 (different layout of various files in /proc) git-svn-id: https://ssl.bulix.org/svn/lcd4linux/trunk@60 3ae390bd-cb1e-0410-b409-cd5a39f66f1f
104 lines
2.6 KiB
C
104 lines
2.6 KiB
C
/* $Id: udelay.c,v 1.2 2000/07/31 10:43:44 reinelt Exp $
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*
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* short delays
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*
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* Copyright 1999, 2000 by Michael Reinelt (reinelt@eunet.at)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*
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* $Log: udelay.c,v $
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* Revision 1.2 2000/07/31 10:43:44 reinelt
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*
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* some changes to support kernel-2.4 (different layout of various files in /proc)
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*
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* Revision 1.1 2000/04/15 16:56:52 reinelt
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*
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* moved delay loops to udelay.c
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* renamed -d (debugging) switch to -v (verbose)
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* new switch -d to calibrate delay loop
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* 'Delay' entry for HD44780 back again
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* delay loops will not calibrate automatically, because this will fail with hich CPU load
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*
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*/
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/*
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*
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* exported fuctions:
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*
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* void udelay (unsigned long usec)
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* delays program execution for usec microseconds
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* uses global variable 'loops_per_usec', which has to be set before.
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* This function does busy-waiting! so use only for delays smaller
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* than 10 msec
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*
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* void udelay_calibrate (void)
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* does a binary approximation for 'loops_per_usec'
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* should be called several times on an otherwise idle machine
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* the maximum value should be used
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*
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <time.h>
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#include "debug.h"
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#include "udelay.h"
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unsigned long loops_per_usec;
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void udelay (unsigned long usec)
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{
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unsigned long loop=usec*loops_per_usec;
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__asm__ (".align 16\n"
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"1:\tdecl %0\n"
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"\tjne 1b"
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: /* no result */
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:"a" (loop));
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}
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/* adopted from /usr/src/linux/init/main.c */
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void udelay_calibrate (void)
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{
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clock_t tick;
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unsigned long bit;
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loops_per_usec=1;
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while (loops_per_usec<<=1) {
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tick=clock();
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while (clock()==tick);
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tick=clock();
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udelay(1000000/CLK_TCK);
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if (clock()>tick)
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break;
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}
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loops_per_usec>>=1;
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bit=loops_per_usec;
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while (bit>>=1) {
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loops_per_usec|=bit;
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tick=clock();
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while (clock()==tick);
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tick=clock();
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udelay(1000000/CLK_TCK);
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if (clock()>tick)
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loops_per_usec&=~bit;
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}
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}
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