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/*
*
* Copyright (C) 2008 Advanced Micro Devices, Inc.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/**
* @file x86/timer.c
* x86 specific timer routines
*/
#include <libpayload.h>
#include <arch/rdtsc.h>
/**
* @ingroup arch
* Global variable containing the speed of the processor in KHz.
*/
uint32_t cpu_khz;
/**
* Calculate the speed of the processor for use in delays.
*
* @return The CPU speed in kHz.
*/
unsigned int get_cpu_speed(void)
{
unsigned long long start, end;
const uint32_t clock_rate = 1193182; // 1.193182 MHz
const uint16_t interval = (2 * clock_rate) / 1000; // 2 ms
/* Set up the PPC port - disable the speaker, enable the T2 gate. */
outb((inb(0x61) & ~0x02) | 0x01, 0x61);
/* Set the PIT to Mode 0, counter 2, word access. */
outb(0xB0, 0x43);
/* Load the interval into the counter. */
outb(interval & 0xff, 0x42);
outb((interval >> 8) & 0xff, 0x42);
/* Read the number of ticks during the period. */
start = rdtsc();
while (!(inb(0x61) & 0x20)) ;
end = rdtsc();
/*
* The number of milliseconds for a period is
* clock_rate / (interval * 1000). Multiply that by the number of
* measured clocks to get the kHz value.
*/
cpu_khz = (end - start) * clock_rate / (1000 * interval);
return cpu_khz;
}
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