diff options
Diffstat (limited to 'arch/x86/kernel/tsc.c')
| -rw-r--r-- | arch/x86/kernel/tsc.c | 61 |
1 files changed, 39 insertions, 22 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 0b29e58f288e..57d87f79558f 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -59,7 +59,7 @@ struct cyc2ns { static DEFINE_PER_CPU_ALIGNED(struct cyc2ns, cyc2ns); -void __always_inline cyc2ns_read_begin(struct cyc2ns_data *data) +__always_inline void cyc2ns_read_begin(struct cyc2ns_data *data) { int seq, idx; @@ -76,7 +76,7 @@ void __always_inline cyc2ns_read_begin(struct cyc2ns_data *data) } while (unlikely(seq != this_cpu_read(cyc2ns.seq.sequence))); } -void __always_inline cyc2ns_read_end(void) +__always_inline void cyc2ns_read_end(void) { preempt_enable_notrace(); } @@ -632,31 +632,38 @@ unsigned long native_calibrate_tsc(void) crystal_khz = ecx_hz / 1000; - if (crystal_khz == 0) { - switch (boot_cpu_data.x86_model) { - case INTEL_FAM6_SKYLAKE_MOBILE: - case INTEL_FAM6_SKYLAKE_DESKTOP: - case INTEL_FAM6_KABYLAKE_MOBILE: - case INTEL_FAM6_KABYLAKE_DESKTOP: - crystal_khz = 24000; /* 24.0 MHz */ - break; - case INTEL_FAM6_ATOM_GOLDMONT_X: - crystal_khz = 25000; /* 25.0 MHz */ - break; - case INTEL_FAM6_ATOM_GOLDMONT: - crystal_khz = 19200; /* 19.2 MHz */ - break; - } - } + /* + * Denverton SoCs don't report crystal clock, and also don't support + * CPUID.0x16 for the calculation below, so hardcode the 25MHz crystal + * clock. + */ + if (crystal_khz == 0 && + boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT_X) + crystal_khz = 25000; - if (crystal_khz == 0) - return 0; /* - * TSC frequency determined by CPUID is a "hardware reported" + * TSC frequency reported directly by CPUID is a "hardware reported" * frequency and is the most accurate one so far we have. This * is considered a known frequency. */ - setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); + if (crystal_khz != 0) + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); + + /* + * Some Intel SoCs like Skylake and Kabylake don't report the crystal + * clock, but we can easily calculate it to a high degree of accuracy + * by considering the crystal ratio and the CPU speed. + */ + if (crystal_khz == 0 && boot_cpu_data.cpuid_level >= 0x16) { + unsigned int eax_base_mhz, ebx, ecx, edx; + + cpuid(0x16, &eax_base_mhz, &ebx, &ecx, &edx); + crystal_khz = eax_base_mhz * 1000 * + eax_denominator / ebx_numerator; + } + + if (crystal_khz == 0) + return 0; /* * For Atom SoCs TSC is the only reliable clocksource. @@ -665,6 +672,16 @@ unsigned long native_calibrate_tsc(void) if (boot_cpu_data.x86_model == INTEL_FAM6_ATOM_GOLDMONT) setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE); +#ifdef CONFIG_X86_LOCAL_APIC + /* + * The local APIC appears to be fed by the core crystal clock + * (which sounds entirely sensible). We can set the global + * lapic_timer_period here to avoid having to calibrate the APIC + * timer later. + */ + lapic_timer_period = crystal_khz * 1000 / HZ; +#endif + return crystal_khz * ebx_numerator / eax_denominator; } |