centrino-decode.c

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/*
 *  (C) 2003 - 2004  Dominik Brodowski <[email protected]>
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *
 * Based on code found in
 * linux/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
 * and originally developed by Jeremy Fitzhardinge.
 *
 * USAGE: simply run it to decode the current settings on CPU 0,
 *    or pass the CPU number as argument, or pass the MSR content
 *    as argument.
 */

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>

#include <sys/types.h>
#include <sys/stat.h>

#define MCPU    32

#define MSR_IA32_PERF_STATUS    0x198

static int rdmsr(unsigned int cpu, unsigned int msr,
         unsigned int *lo, unsigned int *hi)
{
    int fd;
    char file[20];
    unsigned long long val;
    int retval = -1;

    *lo = *hi = 0;

    if (cpu > MCPU)
        goto err1;

    sprintf(file, "/dev/cpu/%d/msr", cpu);
    fd = open(file, O_RDONLY);

    if (fd < 0)
        goto err1;

    if (lseek(fd, msr, SEEK_CUR) == -1)
        goto err2;

    if (read(fd, &val, 8) != 8)
        goto err2;

    *lo = (uint32_t )(val & 0xffffffffull);
    *hi = (uint32_t )(val>>32 & 0xffffffffull);

    retval = 0;
err2:
    close(fd);
err1:
    return retval;
}

static void decode (unsigned int msr)
{
    unsigned int multiplier;
    unsigned int mv;

    multiplier = ((msr >> 8) & 0xFF);

    mv = (((msr & 0xFF) * 16) + 700);

    printf("0x%x means multiplier %d @ %d mV\n", msr, multiplier, mv);
}

static int decode_live(unsigned int cpu)
{
    unsigned int lo, hi;
    int err;

    err = rdmsr(cpu, MSR_IA32_PERF_STATUS, &lo, &hi);

    if (err) {
        printf("can't get MSR_IA32_PERF_STATUS for cpu %d\n", cpu);
        printf("Possible trouble: you don't run an Enhanced SpeedStep capable cpu\n");
        printf("or you are not root, or the msr driver is not present\n");
        return 1;
    }

    decode(lo);

    return 0;
}

int main (int argc, char **argv)
{
    unsigned int cpu, mode = 0;

    if (argc < 2)
        cpu = 0;
    else {
        cpu = strtoul(argv[1], NULL, 0);
        if (cpu >= MCPU)
            mode = 1;
    }

    if (mode)
        decode(cpu);
    else
        decode_live(cpu);

    return 0;
}