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/* $Id: udelay.c 789 2007-04-30 04:48:10Z michael $
* $URL: https://ssl.bulix.org/svn/lcd4linux/branches/0.10.1/udelay.c $
*
* short delays
*
* Copyright (C) 1999, 2000 Michael Reinelt <reinelt@eunet.at>
* Copyright (C) 2004 The LCD4Linux Team <lcd4linux-devel@users.sourceforge.net>
*
* 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.
*
*/
/*
*
* exported fuctions:
*
* void udelay_init (void)
* selects delay method (gettimeofday() ord rdtsc() according
* to processor features
*
* unsigned long timing (const char *driver, const char *section, const char *name, const int defval, const char *unit);
* returns a timing value from config or the default value
*
* 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
*
*/
#include "config.h"
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <sys/time.h>
#ifdef HAVE_ASM_MSR_H
#define u32 unsigned int
#include <asm/msr.h>
#endif
#include "debug.h"
#include "cfg.h"
#include "qprintf.h"
#include "udelay.h"
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("udelay: open(/proc/cpuinfo) failed: %s", strerror(errno));
return;
}
if (read(fd, &buffer, sizeof(buffer) - 1) == -1) {
error("udelay: read(/proc/cpuinfo) failed: %s", strerror(errno));
close(fd);
return;
}
close(fd);
p = strstr(buffer, "flags");
if (p == NULL) {
info("udelay: /proc/cpuinfo has no 'flags' line");
} else {
p = strstr(p, "tsc");
if (p == NULL) {
info("udelay: CPU does not support Time Stamp Counter");
} else {
info("udelay: CPU supports Time Stamp Counter");
*hasTSC = 1;
}
}
p = strstr(buffer, "cpu MHz");
if (p == NULL) {
info("udelay: /proc/cpuinfo has no 'cpu MHz' line");
} else {
if (sscanf(p + 7, " : %lf", MHz) != 1) {
error("udelay: parse(/proc/cpuinfo) failed: unknown 'cpu MHz' format");
*MHz = -1;
} else {
info("udelay: 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("udelay: using TSC delay loop, %u ticks per microsecond", ticks_per_usec);
} else
#else
error("udelay: The file 'include/asm/msr.h' was missing at compile time.");
error("udelay: Even if your CPU supports TSC, it will not be used!");
error("udelay: You *really* should install msr.h and recompile LCD4linux!");
#endif
{
ticks_per_usec = 0;
info("udelay: using gettimeofday() delay loop");
}
}
unsigned long timing(const char *driver, const char *section, const char *name, const int defval, const char *unit)
{
char sec[256];
int fuzz, val;
qprintf(sec, sizeof(sec), "%s.Timing", section);
/* fuzz all timings by given factor */
cfg_number(sec, "fuzz", 100, 1, -1, &fuzz);
cfg_number(sec, name, defval, 0, -1, &val);
val = val * fuzz / 100;
if (val != defval) {
if (fuzz != 100) {
info("%s: timing: %6s = %5d %s (default %d %s, fuzz %d)", driver, name, val, unit, defval, unit, fuzz);
} else {
info("%s: timing: %6s = %5d %s (default %d %s)", driver, name, val, unit, defval, unit);
}
} else {
info("%s: timing: %6s = %5d %s (default)", driver, name, defval, unit);
}
return val;
}
void ndelay(const unsigned long nsec)
{
#ifdef HAVE_ASM_MSR_H
if (ticks_per_usec) {
unsigned int t1, t2;
unsigned long tsc;
tsc = (nsec * ticks_per_usec + 999) / 1000;
rdtscl(t1);
do {
rep_nop();
rdtscl(t2);
} while ((t2 - t1) < tsc);
} 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);
}
}
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