/* * This file is part of the libpayload project. * * 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; }