/* $Id: udelay.c,v 1.16 2004/04/12 05:14:42 reinelt Exp $
*
* short delays
*
* Copyright 1999, 2000 Michael Reinelt <reinelt@eunet.at>
*
* This file is part of LCD4Linux.
*
* LCD4Linux 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.
*
* LCD4Linux 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 1.16 2004/04/12 05:14:42 reinelt
* another BIG FAT WARNING on the use of raw ports instead of ppdev
*
* Revision 1.15 2004/04/12 04:56:00 reinelt
* emitted a BIG FAT WARNING if msr.h could not be found (and therefore
* the gettimeofday() delay loop would be used)
*
* Revision 1.14 2003/10/12 04:46:19 reinelt
*
*
* first try to integrate the Evaluator into a display driver (MatrixOrbital here)
* small warning in processor.c fixed (thanks to Zachary Giles)
* workaround for udelay() on alpha (no msr.h avaliable) (thanks to Zachary Giles)
*
* Revision 1.13 2003/10/05 17:58:50 reinelt
* libtool junk; copyright messages cleaned up
*
* Revision 1.12 2003/07/18 04:43:14 reinelt
* udelay: unnecessary sanity check removed
*
* Revision 1.11 2003/04/04 06:02:04 reinelt
* new parallel port abstraction scheme
*
* Revision 1.10 2003/02/27 07:43:11 reinelt
*
* asm/msr.h: included hard-coded definition of rdtscl() if msr.h cannot be found.
*
* autoconf/automake/autoanything: switched back to 1.4. Hope it works again.
*
* Revision 1.9 2002/08/21 06:09:53 reinelt
* some T6963 fixes, ndelay wrap
*
* Revision 1.8 2002/08/17 14:14:21 reinelt
*
* USBLCD fixes
*
* Revision 1.7 2002/04/29 11:00:28 reinelt
*
* added Toshiba T6963 driver
* added ndelay() with nanosecond resolution
*
* Revision 1.6 2001/08/08 05:40:24 reinelt
*
* renamed CLK_TCK to CLOCKS_PER_SEC
*
* Revision 1.5 2001/03/12 13:44:58 reinelt
*
* new udelay() using Time Stamp Counters
*
* Revision 1.4 2001/03/12 12:39:36 reinelt
*
* reworked autoconf a lot: drivers may be excluded, #define's went to config.h
*
* 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) (if USE_OLD_UDELAY is defined)
* does a binary approximation for 'loops_per_usec'
* should be called several times on an otherwise idle machine
* the maximum value should be used
*
* void udelay_init (void)
* selects delay method (gettimeofday() ord rdtsc() according
* to processor features
*
*/
#include "config.h"
#include <stdlib.h>
#include <stdio.h>
#ifdef USE_OLD_UDELAY
#include <time.h>
#else
#include <math.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>
#ifdef HAVE_ASM_MSR_H
#include <asm/msr.h>
#endif
#endif
#include "debug.h"
#include "udelay.h"
#ifdef USE_OLD_UDELAY
unsigned long loops_per_usec;
void ndelay (unsigned long nsec)
{
unsigned long loop=(nsec*loops_per_usec+999)/1000;
__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();
ndelay(1000000000/CLOCKS_PER_SEC);
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();
ndelay(1000000000/CLOCKS_PER_SEC);
if (clock()>tick)
loops_per_usec&=~bit;
}
}
#else
static unsigned int ticks_per_usec=0;
static void getCPUinfo (int *hasTSC, double *MHz)
{
int fd;
char buffer[4096], *p;
*hasTSC=0;
*MHz=-1;
fd=open("/proc/cpuinfo", O_RDONLY);
if (fd==-1) {
error ("open(/proc/cpuinfo) failed: %s", strerror(errno));
return;
}
if (read (fd, &buffer, sizeof(buffer)-1)==-1) {
error ("read(/proc/cpuinfo) failed: %s", strerror(errno));
close (fd);
return;
}
close (fd);
p=strstr(buffer, "flags");
if (p==NULL) {
info ("/proc/cpuinfo has no 'flags' line");
} else {
p=strstr(p, "tsc");
if (p==NULL) {
info ("CPU does not support Time Stamp Counter");
} else {
info ("CPU supports Time Stamp Counter");
*hasTSC=1;
}
}
p=strstr(buffer, "cpu MHz");
if (p==NULL) {
info ("/proc/cpuinfo has no 'cpu MHz' line");
} else {
if (sscanf(p+7, " : %lf", MHz)!=1) {
error ("parse(/proc/cpuinfo) failed: unknown 'cpu MHz' format");
*MHz=-1;
} else {
info ("CPU runs at %f MHz", *MHz);
}
}
}
void udelay_init (void)
{
#ifdef HAVE_ASM_MSR_H
int tsc;
double mhz;
getCPUinfo (&tsc, &mhz);
if (tsc && mhz>0.0) {
ticks_per_usec=ceil(mhz);
info ("using TSC delay loop, %u ticks per microsecond", ticks_per_usec);
} else
#else
error ("The file 'include/asm/msr.h' was missing at compile time.");
error ("Even if your CPU supports TSC, it will not be used!");
error ("You *really* should install msr.h and recompile LCD4linux!");
#endif
{
ticks_per_usec=0;
info ("using gettimeofday() delay loop");
}
}
void ndelay (unsigned long nsec)
{
#ifdef HAVE_ASM_MSR_H
if (ticks_per_usec) {
unsigned int t1, t2;
nsec=(nsec*ticks_per_usec+999)/1000;
rdtscl(t1);
do {
rep_nop();
rdtscl(t2);
} while ((t2-t1)<nsec);
} else
#endif
{
struct timeval now, end;
gettimeofday (&end, NULL);
end.tv_usec+=(nsec+999)/1000;
while (end.tv_usec>1000000) {
end.tv_usec-=1000000;
end.tv_sec++;
}
do {
rep_nop();
gettimeofday(&now, NULL);
} while (now.tv_sec==end.tv_sec?now.tv_usec<end.tv_usec:now.tv_sec<end.tv_sec);
}
}
#endif