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Diffstat (limited to 'arch/x86/kernel/tsc.c')
-rw-r--r--arch/x86/kernel/tsc.c61
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;
}