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authorSrinivas Pandruvada <srinivas.pandruvada@linux.intel.com>2015-10-15 12:34:21 -0700
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-10-15 22:46:33 +0200
commit8e601a9f97a00bab031980de34f9a81891c1f82f (patch)
tree9116b294513ac173b61dffe4c8daa05802072d68
parent25cb62b76430a91cc6195f902e61c2cb84ade622 (diff)
downloadop-kernel-dev-8e601a9f97a00bab031980de34f9a81891c1f82f.zip
op-kernel-dev-8e601a9f97a00bab031980de34f9a81891c1f82f.tar.gz
cpufreq: intel_pstate: Fix divide by zero on Knights Landing (KNL)
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 <srinivas.pandruvada@linux.intel.com> Acked-by: Kristen Carlson Accardi <kristen@linux.intel.com> Cc: 4.1+ <stable@vger.kernel.org> # 4.1+ Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
-rw-r--r--drivers/cpufreq/intel_pstate.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 3af9dd7..aa33b92 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -776,6 +776,11 @@ 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;
+ }
+
tsc = rdtsc();
local_irq_restore(flags);
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