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
  28 static 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;
  57 err2:
  58         close(fd);
  59 err1:
  60         return retval;
  61 }
  62
  63 static 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
  75 static 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
  94 int 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 }