src/soc/intel/common/block/timer/timer.c

   1 /*
   2  * This file is part of the coreboot project.
   3  *
   4  * Copyright (C) 2017-2019 Intel Corporation.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; version 2 of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  */
  15
  16 #include <arch/cpu.h>
  17 #include <arch/intel-family.h>
  18 #include <cpu/cpu.h>
  19 #include <cpu/x86/msr.h>
  20 #include <cpu/x86/tsc.h>
  21 #include <intelblocks/msr.h>
  22
  23 static int get_processor_model(void)
  24 {
  25         struct cpuinfo_x86 c;
  26
  27         get_fms(&c, cpuid_eax(1));
  28
  29         return c.x86_model;
  30 }
  31
  32 /*
  33  * Nominal TSC frequency = "core crystal clock frequency" * EBX/EAX
  34  *
  35  * Time Stamp Counter
  36  * CPUID Initial EAX value = 0x15
  37  * EAX Bit 31-0 : An unsigned integer which is the denominator of the
  38  * TSC/"core crystal clock" ratio
  39  * EBX Bit 31-0 : An unsigned integer which is the numerator of the
  40  * TSC/"core crystal clock" ratio
  41  * ECX Bit 31-0 : An unsigned integer which is the nominal frequency of the
  42  * core crystal clock in Hz.
  43  * EDX Bit 31-0 : Reserved = 0
  44  *
  45  * Refer to Intel SDM Jan 2019 Vol 3B Section 18.7.3
  46  */
  47 unsigned long tsc_freq_mhz(void)
  48 {
  49         unsigned int core_crystal_nominal_freq_khz;
  50         struct cpuid_result cpuidr;
  51
  52         /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
  53         cpuidr = cpuid(0x15);
  54
  55         if (!cpuidr.ebx || !cpuidr.eax)
  56                 return 0;
  57
  58         core_crystal_nominal_freq_khz = cpuidr.ecx / 1000;
  59
  60         if (!core_crystal_nominal_freq_khz) {
  61                 switch (get_processor_model()) {
  62                 case CPU_MODEL_INTEL_SKYLAKE_MOBILE:
  63                 case CPU_MODEL_INTEL_SKYLAKE_DESKTOP:
  64                 case CPU_MODEL_INTEL_KABYLAKE_MOBILE:
  65                 case CPU_MODEL_INTEL_KABYLAKE_DESKTOP:
  66                 case CPU_MODEL_INTEL_CANNONLAKE_MOBILE:
  67                 case CPU_MODEL_INTEL_ICELAKE_MOBILE:
  68                         core_crystal_nominal_freq_khz = 24000;
  69                         break;
  70                 case CPU_MODEL_INTEL_ATOM_DENVERTON:
  71                         core_crystal_nominal_freq_khz = 25000;
  72                         break;
  73                 case CPU_MODEL_INTEL_ATOM_GOLDMONT:
  74                 case CPU_MODEL_INTEL_ATOM_GEMINI_LAKE:
  75                         core_crystal_nominal_freq_khz = 19200;
  76                         break;
  77                 }
  78         }
  79
  80         return (core_crystal_nominal_freq_khz * cpuidr.ebx / cpuidr.eax) /
  81                         1000;
  82 }