[PATCH] cpufreq: intel_pstate: divide by zero on Knights Landing (KNL)
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From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Date: 2015-10-15 18:33:34
Subsystem:
cpu frequency scaling framework, intel pstate driver, the rest · Maintainers:
"Rafael J. Wysocki", Viresh Kumar, Srinivas Pandruvada, Len Brown, Linus Torvalds
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. Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> --- 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 3af9dd7..d4126e1 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c@@ -776,6 +776,9 @@ 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) + return; + tsc = rdtsc(); local_irq_restore(flags);
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1.9.3