2 * This file is part of the libpayload project.
4 * Copyright (C) 2008 Advanced Micro Devices, Inc.
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. The name of the author may not be used to endorse or promote products
15 * derived from this software without specific prior written permission.
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * i386 specific timer routines
35 #include <libpayload.h>
36 #include <arch/rdtsc.h>
40 * Global variable containing the speed of the processor in KHz.
45 * Calculate the speed of the processor for use in delays.
47 * @return The CPU speed in kHz.
49 unsigned int get_cpu_speed(void)
51 unsigned long long start, end;
53 /* Set up the PPC port - disable the speaker, enable the T2 gate. */
54 outb((inb(0x61) & ~0x02) | 0x01, 0x61);
56 /* Set the PIT to Mode 0, counter 2, word access. */
59 /* Load the counter with 0xffff. */
63 /* Read the number of ticks during the period. */
65 while (!(inb(0x61) & 0x20)) ;
69 * The clock rate is 1193180 Hz, the number of milliseconds for a
70 * period of 0xffff is 1193180 / (0xFFFF * 1000) or .0182.
71 * Multiply that by the number of measured clocks to get the kHz value.
73 cpu_khz = (unsigned int)((end - start) * 1193180U / (1000 * 0xffff));
78 static inline void _delay(unsigned long long delta)
80 unsigned long long timeout = rdtsc() + delta;
81 while (rdtsc() < timeout) ;
85 * Delay for a specified number of nanoseconds.
87 * @param n Number of nanoseconds to delay for.
89 void ndelay(unsigned int n)
91 _delay((unsigned long long)n * cpu_khz / 1000000);
95 * Delay for a specified number of microseconds.
97 * @param n Number of microseconds to delay for.
99 void udelay(unsigned int n)
101 _delay((unsigned long long)n * cpu_khz / 1000);
105 * Delay for a specified number of milliseconds.
107 * @param m Number of milliseconds to delay for.
109 void mdelay(unsigned int m)
111 _delay((unsigned long long)m * cpu_khz);
115 * Delay for a specified number of seconds.
117 * @param s Number of seconds to delay for.
119 void delay(unsigned int s)
122 for (i=0; i<1000; i++)
123 _delay((unsigned long long)s * cpu_khz);