From 4ab60c3f32c721e46217e762bcd3e55a8f659c04 Mon Sep 17 00:00:00 2001 From: Stratos Karafotis Date: Fri, 18 Jul 2014 08:37:24 -0700 Subject: [PATCH] cpufreq: intel_pstate: Disable interrupts during MSRs reading According to Intel 64 and IA-32 Architectures SDM, Volume 3, Chapter 14.2, "Software needs to exercise care to avoid delays between the two RDMSRs (for example interrupts)". So, disable interrupts during reading MSRs IA32_APERF and IA32_MPERF. This should increase the accuracy of the calculations. Signed-off-by: Stratos Karafotis Signed-off-by: Dirk Brandewie Signed-off-by: Rafael J. Wysocki --- drivers/cpufreq/intel_pstate.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 9d75bd6faf65..ff3c5624972c 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -577,9 +577,12 @@ static inline void intel_pstate_calc_busy(struct cpudata *cpu) static inline void intel_pstate_sample(struct cpudata *cpu) { u64 aperf, mperf; + unsigned long flags; + local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); + local_irq_restore(flags); aperf = aperf >> FRAC_BITS; mperf = mperf >> FRAC_BITS; -- 2.11.0