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/* SPDX-License-Identifier: GPL-2.0-only */
/* This file is part of the coreboot project. */
#include <arch/cpu.h>
#include <cpu/x86/msr.h>
#include <cpu/x86/tsc.h>
#include <intelblocks/msr.h>
/* Goldmont Microserver */
#define CPU_MODEL_INTEL_ATOM_DENVERTON 0x5F
static int get_processor_model(void)
{
struct cpuinfo_x86 c;
get_fms(&c, cpuid_eax(1));
return c.x86_model;
}
static unsigned long get_hardcoded_crystal_freq(void)
{
unsigned long core_crystal_nominal_freq_khz = 0;
/*
* Denverton SoCs don't report crystal clock, and also don't support
* CPUID.0x16, so hardcode the 25MHz crystal clock.
*/
switch (get_processor_model()) {
case CPU_MODEL_INTEL_ATOM_DENVERTON:
core_crystal_nominal_freq_khz = 25000;
break;
}
return core_crystal_nominal_freq_khz;
}
/*
* Nominal TSC frequency = "core crystal clock frequency" *
* CPUID_15h.EBX/CPUID_15h.EAX
*
* Time Stamp Counter
* CPUID Initial EAX value = 0x15
* EAX Bit 31-0 : An unsigned integer which is the denominator of the
* TSC/"core crystal clock" ratio
* EBX Bit 31-0 : An unsigned integer which is the numerator of the
* TSC/"core crystal clock" ratio
* ECX Bit 31-0 : An unsigned integer which is the nominal frequency of the
* core crystal clock in Hz.
* EDX Bit 31-0 : Reserved = 0
*
*/
static unsigned long calculate_tsc_freq_from_core_crystal(void)
{
unsigned long core_crystal_nominal_freq_khz;
struct cpuid_result cpuidr_15h;
if (cpuid_get_max_func() < 0x15)
return 0;
/* CPUID 15H TSC/Crystal ratio, plus optionally Crystal Hz */
cpuidr_15h = cpuid(0x15);
if (!cpuidr_15h.ebx || !cpuidr_15h.eax)
return 0;
core_crystal_nominal_freq_khz = cpuidr_15h.ecx / 1000;
if (!core_crystal_nominal_freq_khz)
core_crystal_nominal_freq_khz = get_hardcoded_crystal_freq();
return (core_crystal_nominal_freq_khz * cpuidr_15h.ebx /
cpuidr_15h.eax) / 1000;
}
/*
* Processor Frequency Information
* CPUID Initial EAX value = 0x16
* EAX Bit 31-0 : An unsigned integer which has the processor base frequency
* information
* EBX Bit 31-0 : An unsigned integer which has maximum frequency information
* ECX Bit 31-0 : An unsigned integer which has bus frequency information
* EDX Bit 31-0 : Reserved = 0
*
* Refer to Intel SDM Jan 2019 Vol 3B Section 18.7.3
*/
static unsigned long get_freq_from_cpuid16h(void)
{
if (cpuid_get_max_func() < 0x16)
return 0;
return cpuid_eax(0x16);
}
unsigned long tsc_freq_mhz(void)
{
unsigned long tsc_freq;
tsc_freq = calculate_tsc_freq_from_core_crystal();
if (tsc_freq)
return tsc_freq;
/*
* Some Intel SoCs like Skylake, Kabylake and Cometlake don't report
* the crystal clock, in that case return bus frequency using CPUID.16h
*/
return get_freq_from_cpuid16h();
}
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