#!/bin/bash

# A wrapper for cpupower to set the appropriate governor for frequency 
# scaling. Sets 'ondemand', 'powersave' or 'performance' if available
# (checks availablility in this order).
# The user can override this behaviour by specifying the governor in 
# CPUPOWER_GOVERNOR variable.
# 
# CPUPOWER_OTHER_ARGS can be used to provide additional arguments to
# cpupower.

AVAIL_FILE=/sys/devices/system/cpu/cpu0/cpufreq/scaling_available_governors
USE_GOVERNOR=""

if ! test -e "${AVAIL_FILE}"; then
	printf "CPU frequency scaling is not supported.\n"
	exit 1
fi

if test -n "${CPUPOWER_GOVERNOR}"; then
	if grep "${CPUPOWER_GOVERNOR}" "${AVAIL_FILE}" >/dev/null 2>&1; then
		USE_GOVERNOR="${CPUPOWER_GOVERNOR}"
	else
		printf "Unknown governor: ${CPUPOWER_GOVERNOR}.\n"
		printf "Available governors: " 
		cat "${AVAIL_FILE}"
		printf "\n"
		exit 1
	fi
elif grep "ondemand" "${AVAIL_FILE}" >/dev/null 2>&1; then
	USE_GOVERNOR=ondemand
elif grep "powersave" "${AVAIL_FILE}" >/dev/null 2>&1; then
	USE_GOVERNOR=powersave
elif grep "performance" "${AVAIL_FILE}" >/dev/null 2>&1; then
	USE_GOVERNOR=performance
else
	printf "Failed to select the governor automatically, "
	printf "please specify it explicitly in CPUPOWER_GOVERNOR variable.\n"
	printf "Available governors: " 
	cat "${AVAIL_FILE}"
	printf "\n"
	exit 1
fi

# Set the governor at last.
printf "Using \"${USE_GOVERNOR}\" governor.\n"
/usr/bin/cpupower frequency-set -g ${USE_GOVERNOR} ${CPUPOWER_OTHER_ARGS}