root/tools/power/cpupower/utils/helpers/msr.c

DEFINITIONS

1. read_msr
2. write_msr
3. msr_intel_get_perf_bias
4. msr_intel_set_perf_bias
5. msr_intel_get_turbo_ratio

   1 // SPDX-License-Identifier: GPL-2.0
   2 #if defined(__i386__) || defined(__x86_64__)
   3 
   4 #include <fcntl.h>
   5 #include <stdio.h>
   6 #include <unistd.h>
   7 #include <stdint.h>
   8 
   9 #include "helpers/helpers.h"
  10 
  11 /* Intel specific MSRs */
  12 #define MSR_IA32_PERF_STATUS            0x198
  13 #define MSR_IA32_MISC_ENABLES           0x1a0
  14 #define MSR_IA32_ENERGY_PERF_BIAS       0x1b0
  15 #define MSR_NEHALEM_TURBO_RATIO_LIMIT   0x1ad
  16 
  17 /*
  18  * read_msr
  19  *
  20  * Will return 0 on success and -1 on failure.
  21  * Possible errno values could be:
  22  * EFAULT -If the read/write did not fully complete
  23  * EIO    -If the CPU does not support MSRs
  24  * ENXIO  -If the CPU does not exist
  25  */
  26 
  27 int read_msr(int cpu, unsigned int idx, unsigned long long *val)
  28 {
  29         int fd;
  30         char msr_file_name[64];
  31 
  32         sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
  33         fd = open(msr_file_name, O_RDONLY);
  34         if (fd < 0)
  35                 return -1;
  36         if (lseek(fd, idx, SEEK_CUR) == -1)
  37                 goto err;
  38         if (read(fd, val, sizeof *val) != sizeof *val)
  39                 goto err;
  40         close(fd);
  41         return 0;
  42  err:
  43         close(fd);
  44         return -1;
  45 }
  46 
  47 /*
  48  * write_msr
  49  *
  50  * Will return 0 on success and -1 on failure.
  51  * Possible errno values could be:
  52  * EFAULT -If the read/write did not fully complete
  53  * EIO    -If the CPU does not support MSRs
  54  * ENXIO  -If the CPU does not exist
  55  */
  56 int write_msr(int cpu, unsigned int idx, unsigned long long val)
  57 {
  58         int fd;
  59         char msr_file_name[64];
  60 
  61         sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
  62         fd = open(msr_file_name, O_WRONLY);
  63         if (fd < 0)
  64                 return -1;
  65         if (lseek(fd, idx, SEEK_CUR) == -1)
  66                 goto err;
  67         if (write(fd, &val, sizeof val) != sizeof val)
  68                 goto err;
  69         close(fd);
  70         return 0;
  71  err:
  72         close(fd);
  73         return -1;
  74 }
  75 
  76 int msr_intel_get_perf_bias(unsigned int cpu)
  77 {
  78         unsigned long long val;
  79         int ret;
  80 
  81         if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_PERF_BIAS))
  82                 return -1;
  83 
  84         ret = read_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS, &val);
  85         if (ret)
  86                 return ret;
  87         return val;
  88 }
  89 
  90 int msr_intel_set_perf_bias(unsigned int cpu, unsigned int val)
  91 {
  92         int ret;
  93 
  94         if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_PERF_BIAS))
  95                 return -1;
  96 
  97         ret = write_msr(cpu, MSR_IA32_ENERGY_PERF_BIAS, val);
  98         if (ret)
  99                 return ret;
 100         return 0;
 101 }
 102 
 103 unsigned long long msr_intel_get_turbo_ratio(unsigned int cpu)
 104 {
 105         unsigned long long val;
 106         int ret;
 107 
 108         if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_HAS_TURBO_RATIO))
 109                 return -1;
 110 
 111         ret = read_msr(cpu, MSR_NEHALEM_TURBO_RATIO_LIMIT, &val);
 112         if (ret)
 113                 return ret;
 114         return val;
 115 }
 116 #endif