cpupower: Add support for setting EPP via systemd service

Extend the systemd service so that it can be used for tuning the Energy
Performance Preference (EPP) as well. Available options can be read from
/sys/devices/system/cpu/cpufreq/policy0/energy_performance_available_preferences.
The desired one can then be set in cpupower-service.conf.

Signed-off-by: Jan Kiszka <[email protected]>
Signed-off-by: Shuah Khan <[email protected]>

Author: jan-kiszka

tools/power/cpupower/cpupower-service.conf

@@ -30,3 +30,8 @@
 # its policy for the relative importance of performance versus energy savings to
 # the processor. See man CPUPOWER-SET(1) for additional details
 #PERF_BIAS=
+
+# Set the Energy Performance Preference
+# Available options can be read from
+# /sys/devices/system/cpu/cpufreq/policy0/energy_performance_available_preferences
+#EPP=

tools/power/cpupower/cpupower.sh

@@ -23,4 +23,10 @@ then
     cpupower set -b "$PERF_BIAS" > /dev/null || ESTATUS=1
 fi
 
+# apply Energy Performance Preference
+if test -n "$EPP"
+then
+    cpupower set -e "$EPP" > /dev/null || ESTATUS=1
+fi
+
 exit $ESTATUS