diff options
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/tsc.c | 12 |
2 files changed, 17 insertions, 1 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7bc83f3d9bdf..409ee4ae467c 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5067,6 +5067,12 @@ interruptions from clocksource watchdog are not acceptable). + tsc_early_khz= [X86] Skip early TSC calibration and use the given + value instead. Useful when the early TSC frequency discovery + procedure is not reliable, such as on overclocked systems + with CPUID.16h support and partial CPUID.15h support. + Format: <unsigned int> + tsx= [X86] Control Transactional Synchronization Extensions (TSX) feature in Intel processors that support TSX control. diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index fdd4c1078632..49d925043171 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -41,6 +41,7 @@ EXPORT_SYMBOL(tsc_khz); * TSC can be unstable due to cpufreq or due to unsynced TSCs */ static int __read_mostly tsc_unstable; +static unsigned int __initdata tsc_early_khz; static DEFINE_STATIC_KEY_FALSE(__use_tsc); @@ -59,6 +60,12 @@ struct cyc2ns { static DEFINE_PER_CPU_ALIGNED(struct cyc2ns, cyc2ns); +static int __init tsc_early_khz_setup(char *buf) +{ + return kstrtouint(buf, 0, &tsc_early_khz); +} +early_param("tsc_early_khz", tsc_early_khz_setup); + __always_inline void cyc2ns_read_begin(struct cyc2ns_data *data) { int seq, idx; @@ -1412,7 +1419,10 @@ static bool __init determine_cpu_tsc_frequencies(bool early) if (early) { cpu_khz = x86_platform.calibrate_cpu(); - tsc_khz = x86_platform.calibrate_tsc(); + if (tsc_early_khz) + tsc_khz = tsc_early_khz; + else + tsc_khz = x86_platform.calibrate_tsc(); } else { /* We should not be here with non-native cpu calibration */ WARN_ON(x86_platform.calibrate_cpu != native_calibrate_cpu); |