/*
 *  $Id: MHz.c,v 1.4 2001/05/21 18:58:01 davej Exp $
 *  This file is part of x86info.
 *  (C) 2001 Dave Jones.
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *
 * Estimate CPU MHz routine by Andrea Arcangeli <andrea@suse.de>
 * Small changes by David Sterba <sterd9am@ss1000.ms.mff.cuni.cz>
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <string.h>
#include <unistd.h>

__inline__ unsigned long long int rdtsc()
{
	unsigned long long int x;
	__asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
	return x;
}

char *estimate_MHz()
{
	char *buffer;
	struct timezone tz;
        struct timeval tvstart, tvstop;
        unsigned long long int cycles[2]; /* gotta be 64 bit */
	unsigned int microseconds; /* total time taken */
	
	memset(&tz, 0, sizeof(tz));

	/* get this function in cached memory */
	gettimeofday(&tvstart, &tz);
	cycles[0] = rdtsc();
	gettimeofday(&tvstart, &tz);

	/* we don't trust that this is any specific length of time */
	usleep(100);
	
	cycles[1] = rdtsc();
	gettimeofday(&tvstop, &tz);
	microseconds = ((tvstop.tv_sec-tvstart.tv_sec)*1000000) +
		(tvstop.tv_usec-tvstart.tv_usec);

	buffer = (char *) malloc(sizeof(char)*512);
	sprintf(buffer, "%lldMHz",
		(cycles[1]-cycles[0])/microseconds);

	return buffer;
}