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| author | Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> | 2015-10-15 12:34:21 -0700 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2015-10-15 22:46:33 +0200 |
| commit | 8e601a9f97a00bab031980de34f9a81891c1f82f (patch) | |
| tree | 9116b294513ac173b61dffe4c8daa05802072d68 /drivers/cpufreq/intel_pstate.c | |
| parent | 25cb62b76430a91cc6195f902e61c2cb84ade622 (diff) | |
| download | lwn-8e601a9f97a00bab031980de34f9a81891c1f82f.tar.gz lwn-8e601a9f97a00bab031980de34f9a81891c1f82f.zip | |
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>
Diffstat (limited to 'drivers/cpufreq/intel_pstate.c')
| -rw-r--r-- | drivers/cpufreq/intel_pstate.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 3af9dd7332e6..aa33b92b3e3e 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); |