/* 
 * Copyright 2010 Stefan Lankes, Chair for Operating Systems,
 *                               RWTH Aachen University
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * This file is part of MetalSVM. 
 */

#include <metalsvm/stddef.h>
#include <metalsvm/stdio.h>
#include <metalsvm/time.h>
#include <metalsvm/processor.h>

static uint32_t cpu_freq = 0;

uint32_t detect_cpu_frequency(void)
{
	uint64_t start, end;
	uint64_t ticks, old;

	old = get_clock_tick();

	/* wait for the next time slice */
	while((ticks = get_clock_tick()) - old == 0)
		;

	start = rdtsc();
	/* wait a second to determine the frequency */
	while(get_clock_tick() - ticks < TIMER_FREQ)
		;
	end = rdtsc();

	cpu_freq = (uint32_t) ((end - start) / (uint64_t) 1000000);

	return cpu_freq;
}

uint32_t get_cpu_frequency(void)
{	
	if (cpu_freq > 0)
		return cpu_freq;

	return detect_cpu_frequency();
}

void udelay(unsigned int usecs)
{
	uint64_t start = rdtsc();
	uint64_t deadline = get_cpu_frequency() * usecs;

	while(rdtsc() - start < deadline)
		;
}