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authorPrakash, Prashanth <pprakash@codeaurora.org>2017-05-11 16:39:44 -0600
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-06-27 02:19:39 +0200
commit73808d0fd26b3d3f0f44cc7c469ad1d3c1b570b8 (patch)
tree3099d7f581101eebeb06cebc9245daf0c9f78ff5 /drivers/cpufreq
parent0370f0f975e5561c658aa86e2c372079e6a425eb (diff)
downloadlinux-73808d0fd26b3d3f0f44cc7c469ad1d3c1b570b8.tar.bz2
cpufreq / CPPC: Initialize policy->min to lowest nonlinear performance
Description of Lowest Perfomance in ACPI 6.1 specification states: "Lowest Performance is the absolute lowest performance level of the platform. Selecting a performance level lower than the lowest nonlinear performance level may actually cause an efficiency penalty, but should reduce the instantaneous power consumption of the processor. In traditional terms, this represents the T-state range of performance levels." Set the default value of policy->min to Lowest Nonlinear Performance to avoid any potential efficiency penalty. Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org> Acked-by: Viresh Kumar <viresh.kumar@linaro.org> Acked-by: Alexey Klimov <alexey.klimov@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/cpufreq')
-rw-r--r--drivers/cpufreq/cppc_cpufreq.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/drivers/cpufreq/cppc_cpufreq.c b/drivers/cpufreq/cppc_cpufreq.c
index e82bb3c30b92..10be285c9055 100644
--- a/drivers/cpufreq/cppc_cpufreq.c
+++ b/drivers/cpufreq/cppc_cpufreq.c
@@ -144,10 +144,23 @@ static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
cppc_dmi_max_khz = cppc_get_dmi_max_khz();
- policy->min = cpu->perf_caps.lowest_perf * cppc_dmi_max_khz / cpu->perf_caps.highest_perf;
+ /*
+ * Set min to lowest nonlinear perf to avoid any efficiency penalty (see
+ * Section 8.4.7.1.1.5 of ACPI 6.1 spec)
+ */
+ policy->min = cpu->perf_caps.lowest_nonlinear_perf * cppc_dmi_max_khz /
+ cpu->perf_caps.highest_perf;
policy->max = cppc_dmi_max_khz;
- policy->cpuinfo.min_freq = policy->min;
- policy->cpuinfo.max_freq = policy->max;
+
+ /*
+ * Set cpuinfo.min_freq to Lowest to make the full range of performance
+ * available if userspace wants to use any perf between lowest & lowest
+ * nonlinear perf
+ */
+ policy->cpuinfo.min_freq = cpu->perf_caps.lowest_perf * cppc_dmi_max_khz /
+ cpu->perf_caps.highest_perf;
+ policy->cpuinfo.max_freq = cppc_dmi_max_khz;
+
policy->cpuinfo.transition_latency = cppc_get_transition_latency(cpu_num);
policy->shared_type = cpu->shared_type;