LXR linux/tools/power/cpupower/debug/i386/centrino-decode.c

   1// SPDX-License-Identifier: GPL-2.0-only
   2/*
   3 *  (C) 2003 - 2004  Dominik Brodowski <linux@dominikbrodowski.de>
   4 *
   5 * Based on code found in
   6 * linux/arch/i386/kernel/cpu/cpufreq/speedstep-centrino.c
   7 * and originally developed by Jeremy Fitzhardinge.
   8 *
   9 * USAGE: simply run it to decode the current settings on CPU 0,
  10 *        or pass the CPU number as argument, or pass the MSR content
  11 *        as argument.
  12 */
  13
  14#include <stdio.h>
  15#include <stdlib.h>
  16#include <stdint.h>
  17#include <unistd.h>
  18#include <errno.h>
  19#include <fcntl.h>
  20
  21#include <sys/types.h>
  22#include <sys/stat.h>
  23
  24#define MCPU    32
  25
  26#define MSR_IA32_PERF_STATUS    0x198
  27
  28static int rdmsr(unsigned int cpu, unsigned int msr,
  29                 unsigned int *lo, unsigned int *hi)
  30{
  31        int fd;
  32        char file[20];
  33        unsigned long long val;
  34        int retval = -1;
  35
  36        *lo = *hi = 0;
  37
  38        if (cpu > MCPU)
  39                goto err1;
  40
  41        sprintf(file, "/dev/cpu/%d/msr", cpu);
  42        fd = open(file, O_RDONLY);
  43
  44        if (fd < 0)
  45                goto err1;
  46
  47        if (lseek(fd, msr, SEEK_CUR) == -1)
  48                goto err2;
  49
  50        if (read(fd, &val, 8) != 8)
  51                goto err2;
  52
  53        *lo = (uint32_t )(val & 0xffffffffull);
  54        *hi = (uint32_t )(val>>32 & 0xffffffffull);
  55
  56        retval = 0;
  57err2:
  58        close(fd);
  59err1:
  60        return retval;
  61}
  62
  63static void decode (unsigned int msr)
  64{
  65        unsigned int multiplier;
  66        unsigned int mv;
  67
  68        multiplier = ((msr >> 8) & 0xFF);
  69
  70        mv = (((msr & 0xFF) * 16) + 700);
  71
  72        printf("0x%x means multiplier %d @ %d mV\n", msr, multiplier, mv);
  73}
  74
  75static int decode_live(unsigned int cpu)
  76{
  77        unsigned int lo, hi;
  78        int err;
  79
  80        err = rdmsr(cpu, MSR_IA32_PERF_STATUS, &lo, &hi);
  81
  82        if (err) {
  83                printf("can't get MSR_IA32_PERF_STATUS for cpu %d\n", cpu);
  84                printf("Possible trouble: you don't run an Enhanced SpeedStep capable cpu\n");
  85                printf("or you are not root, or the msr driver is not present\n");
  86                return 1;
  87        }
  88
  89        decode(lo);
  90
  91        return 0;
  92}
  93
  94int main (int argc, char **argv)
  95{
  96        unsigned int cpu, mode = 0;
  97
  98        if (argc < 2)
  99                cpu = 0;
 100        else {
 101                cpu = strtoul(argv[1], NULL, 0);
 102                if (cpu >= MCPU)
 103                        mode = 1;
 104        }
 105
 106        if (mode)
 107                decode(cpu);
 108        else
 109                decode_live(cpu);
 110
 111        return 0;
 112}
 113