From: Srinivas Pandruvada Date: Thu, 15 Oct 2015 19:34:21 +0000 (-0700) Subject: cpufreq: intel_pstate: Fix divide by zero on Knights Landing (KNL) X-Git-Tag: v4.1.12-92~201^2~68 X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=0bba0b7bd50d0e1d46c5eec25ace72711df4dc01;p=users%2Fjedix%2Flinux-maple.git cpufreq: intel_pstate: Fix divide by zero on Knights Landing (KNL) Orabug: 22623827 commit 8e601a9f97a00bab031980de34f9a81891c1f82f upstream. This is a workaround for KNL platform, where in some cases MPERF counter will not have updated value before next read of MSR_IA32_MPERF. In this case divide by zero will occur. This change ignores current sample for busy calculation in this case. Fixes: b34ef932d79a (intel_pstate: Knights Landing support) Signed-off-by: Srinivas Pandruvada Acked-by: Kristen Carlson Accardi Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman (cherry picked from commit 82696471b9c72e4b996e009bb6b4ee432c175582) Signed-off-by: Dan Duval --- diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index e8d16997c5cbc..1ee2ab58e37d6 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -761,6 +761,11 @@ static inline void intel_pstate_sample(struct cpudata *cpu) local_irq_save(flags); rdmsrl(MSR_IA32_APERF, aperf); rdmsrl(MSR_IA32_MPERF, mperf); + if (cpu->prev_mperf == mperf) { + local_irq_restore(flags); + return; + } + local_irq_restore(flags); cpu->last_sample_time = cpu->sample.time;