| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.1 75/86] cpufreq: intel_pstate: Fix divide by zero on Knights Landing (KNL) | Date | Fri, 6 Nov 2015 11:23:14 -0800 |
| |
4.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
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 <srinivas.pandruvada@linux.intel.com> Acked-by: Kristen Carlson Accardi <kristen@linux.intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/cpufreq/intel_pstate.c | 5 +++++ 1 file changed, 5 insertions(+)
--- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -761,6 +761,11 @@ static inline void intel_pstate_sample(s 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;
|