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cpufreq: conservative: Fix sampling_down_factor functionality 

sampling_down_factor tunable is unused since commit
8e677ce83b (4 years ago).

This patch restores the original functionality and documents the
tunable.

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
hifive-unleashed-5.1
Stratos Karafotis 2013-03-05 22:06:29 +00:00 committed by Rafael J. Wysocki
parent 9366d84052
commit 7af1c0568d
2 changed files with 14 additions and 3 deletions
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6
Documentation/cpu-freq/governors.txt
View File

@ -191,6 +191,12 @@ governor but for the opposite direction. For example when set to its
default value of '20' it means that if the CPU usage needs to be below
20% between samples to have the frequency decreased.
sampling_down_factor: similar functionality as in "ondemand" governor.
But in "conservative", it controls the rate at which the kernel makes
a decision on when to decrease the frequency while running in any
speed. Load for frequency increase is still evaluated every
sampling rate.
3. The Governor Interface in the CPUfreq Core
=============================================

11
drivers/cpufreq/cpufreq_conservative.c
View File

@ -36,9 +36,9 @@ static DEFINE_PER_CPU(struct cs_cpu_dbs_info_s, cs_cpu_dbs_info);
/*
* Every sampling_rate, we check, if current idle time is less than 20%
* (default), then we try to increase frequency Every sampling_rate *
* sampling_down_factor, we check, if current idle time is more than 80%, then
* we try to decrease frequency
* (default), then we try to increase frequency. Every sampling_rate *
* sampling_down_factor, we check, if current idle time is more than 80%
* (default), then we try to decrease frequency
*
* Any frequency increase takes it to the maximum frequency. Frequency reduction
* happens at minimum steps of 5% (default) of maximum frequency
@ -81,6 +81,11 @@ static void cs_check_cpu(int cpu, unsigned int load)
return;
}
/* if sampling_down_factor is active break out early */
if (++dbs_info->down_skip < cs_tuners->sampling_down_factor)
return;
dbs_info->down_skip = 0;
/*
* The optimal frequency is the frequency that is the lowest that can
* support the current CPU usage without triggering the up policy. To be