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

   1 /*
   2  * This file is part of the coreboot project.
   3  *
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; version 2 of the License.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  */
  14
  15 #include <arch/cpu.h>
  16 #include <cpu/x86/msr.h>
  17 #include <cpu/x86/tsc.h>
  18 #include <intelblocks/msr.h>
  19
  20 /* Goldmont Microserver */
  21 #define CPU_MODEL_INTEL_ATOM_DENVERTON 0x5F
  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 static unsigned long get_hardcoded_crystal_freq(void)
  33 {
  34         unsigned long core_crystal_nominal_freq_khz = 0;
  35
  36         /*
  37          * Denverton SoCs don't report crystal clock, and also don't support
  38          * CPUID.0x16, so hardcode the 25MHz crystal clock.
  39          */
  40         switch (get_processor_model()) {
  41         case CPU_MODEL_INTEL_ATOM_DENVERTON:
  42                 core_crystal_nominal_freq_khz = 25000;
  43                 break;
  44         }
  45
  46         return core_crystal_nominal_freq_khz;
  47 }
  48
  49 /*
  50  * Nominal TSC frequency = "core crystal clock frequency" *
  51  *                               CPUID_15h.EBX/CPUID_15h.EAX
  52  *
  53  * Time Stamp Counter
  54  * CPUID Initial EAX value = 0x15
  55  * EAX Bit 31-0 : An unsigned integer which is the denominator of the
  56  * TSC/"core crystal clock" ratio
  57  * EBX Bit 31-0 : An unsigned integer which is the numerator of the
  58  * TSC/"core crystal clock" ratio
  59  * ECX Bit 31-0 : An unsigned integer which is the nominal frequency of the
  60  * core crystal clock in Hz.
  61  * EDX Bit 31-0 : Reserved = 0
  62  *
  63  */
  64 static unsigned long calculate_tsc_freq_from_core_crystal(void)
  65 {
  66         unsigned long core_crystal_nominal_freq_khz;
  67         struct cpuid_result cpuidr_15h;
  68
  69         if (cpuid_get_max_func() < 0x15)
  70                 return 0;
  71
  72         /* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
  73         cpuidr_15h = cpuid(0x15);
  74
  75         if (!cpuidr_15h.ebx || !cpuidr_15h.eax)
  76                 return 0;
  77
  78         core_crystal_nominal_freq_khz = cpuidr_15h.ecx / 1000;
  79
  80         if (!core_crystal_nominal_freq_khz)
  81                 core_crystal_nominal_freq_khz = get_hardcoded_crystal_freq();
  82
  83         return (core_crystal_nominal_freq_khz * cpuidr_15h.ebx /
  84                         cpuidr_15h.eax) / 1000;
  85 }
  86
  87 /*
  88  * Processor Frequency Information
  89  * CPUID Initial EAX value = 0x16
  90  * EAX Bit 31-0 : An unsigned integer which has the processor base frequency
  91  * information
  92  * EBX Bit 31-0 : An unsigned integer which has maximum frequency information
  93  * ECX Bit 31-0 : An unsigned integer which has bus frequency information
  94  * EDX Bit 31-0 : Reserved = 0
  95  *
  96  * Refer to Intel SDM Jan 2019 Vol 3B Section 18.7.3
  97  */
  98 static unsigned long get_freq_from_cpuid16h(void)
  99 {
 100         if (cpuid_get_max_func() < 0x16)
 101                 return 0;
 102
 103         return cpuid_eax(0x16);
 104 }
 105
 106 unsigned long tsc_freq_mhz(void)
 107 {
 108         unsigned long tsc_freq;
 109
 110         tsc_freq = calculate_tsc_freq_from_core_crystal();
 111
 112         if (tsc_freq)
 113                 return tsc_freq;
 114
 115         /*
 116          * Some Intel SoCs like Skylake, Kabylake and Cometlake don't report
 117          * the crystal clock, in that case return bus frequency using CPUID.16h
 118          */
 119         return get_freq_from_cpuid16h();
 120 }