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_NEHALEM_TURBO_RATIO_LIMIT   0x1ad
  15
  16 /*
  17  * read_msr
  18  *
  19  * Will return 0 on success and -1 on failure.
  20  * Possible errno values could be:
  21  * EFAULT -If the read/write did not fully complete
  22  * EIO    -If the CPU does not support MSRs
  23  * ENXIO  -If the CPU does not exist
  24  */
  25
  26 int read_msr(int cpu, unsigned int idx, unsigned long long *val)
  27 {
  28         int fd;
  29         char msr_file_name[64];
  30
  31         sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
  32         fd = open(msr_file_name, O_RDONLY);
  33         if (fd < 0)
  34                 return -1;
  35         if (lseek(fd, idx, SEEK_CUR) == -1)
  36                 goto err;
  37         if (read(fd, val, sizeof *val) != sizeof *val)
  38                 goto err;
  39         close(fd);
  40         return 0;
  41  err:
  42         close(fd);
  43         return -1;
  44 }
  45
  46 /*
  47  * write_msr
  48  *
  49  * Will return 0 on success and -1 on failure.
  50  * Possible errno values could be:
  51  * EFAULT -If the read/write did not fully complete
  52  * EIO    -If the CPU does not support MSRs
  53  * ENXIO  -If the CPU does not exist
  54  */
  55 int write_msr(int cpu, unsigned int idx, unsigned long long val)
  56 {
  57         int fd;
  58         char msr_file_name[64];
  59
  60         sprintf(msr_file_name, "/dev/cpu/%d/msr", cpu);
  61         fd = open(msr_file_name, O_WRONLY);
  62         if (fd < 0)
  63                 return -1;
  64         if (lseek(fd, idx, SEEK_CUR) == -1)
  65                 goto err;
  66         if (write(fd, &val, sizeof val) != sizeof val)
  67                 goto err;
  68         close(fd);
  69         return 0;
  70  err:
  71         close(fd);
  72         return -1;
  73 }
  74
  75 unsigned long long msr_intel_get_turbo_ratio(unsigned int cpu)
  76 {
  77         unsigned long long val;
  78         int ret;
  79
  80         if (!(cpupower_cpu_info.caps & CPUPOWER_CAP_HAS_TURBO_RATIO))
  81                 return -1;
  82
  83         ret = read_msr(cpu, MSR_NEHALEM_TURBO_RATIO_LIMIT, &val);
  84         if (ret)
  85                 return ret;
  86         return val;
  87 }
  88 #endif