LXR linux/tools/power/cpupower/utils/helpers/msr.c

   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
  27int 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 */
  56int 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
  76int 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
  90int 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
 103unsigned 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
 117