/*
 *  $Id: MHz.c,v 1.3 2003/06/09 22:02:36 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 <sys/time.h>
#include <string.h>
#include <unistd.h>

#include "../x86info.h"

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

void estimate_MHz(struct cpudata *cpu)
{
	struct timezone tz;
	struct timeval tvstart, tvstop;
	unsigned long long int cycles[2]; /* gotta be 64 bit */
	unsigned long microseconds; /* total time taken */
	unsigned long eax, ebx, ecx, edx;
	unsigned long freq = 1;

	/* Make sure we have a TSC (and hence RDTSC) */
	cpuid (cpu->number, 1, &eax, &ebx, &ecx, &edx);
	if ((edx & (1<<4))==0) {
		printf ("No TSC, MHz calculation cannot be performed.\n");
		cpu->MHz = 0;
		return;
	}

	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(250000);

	gettimeofday(&tvstop, &tz);
	cycles[1] = rdtsc();
	gettimeofday(&tvstop, &tz);

	microseconds = ((tvstop.tv_sec-tvstart.tv_sec)*1000000) +
		(tvstop.tv_usec-tvstart.tv_usec);

	cpu->MHz = (int) (cycles[1]-cycles[0]) / (microseconds/freq);

	if ((cpu->MHz % 50) > 15)
		cpu->MHz = ((cpu->MHz / 50) * 50) + 50;
	else
		cpu->MHz = ((cpu->MHz / 50) * 50);
}