#!/usr/bin/perl -w

# A script to measure fan response to PWM at different frequencies
# Copyright 2006-2007 Jean Delvare <khali@linux-fr.org>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, version 2.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

use vars qw($hwmon_dev $fan_file $pwm_file $freq_file @freqs $output_file);
use strict;

use constant SLEEP => 4;

@freqs = (160000, 40000, 10000, 2000, 700, 500, 300, 100, 60, 30);

$hwmon_dev = "/sys/class/hwmon/hwmon1/device";
$fan_file = "fan1_input";
$pwm_file = "pwm1";
$freq_file = "pwm1_freq";
$output_file = "/tmp/pwm_response.csv";

sub read_value($)
{
	my $filename = shift;
	my $value;

	open(local *FILE, $filename);
	$value = <FILE>;
	close(FILE);
	chomp $value;

	return $value;
}

open(CSV, ">$output_file") or die;
# Print header
for (my $pwm = 248; $pwm; $pwm -= 8) {
	print CSV ";$pwm";
}
print CSV "\n";

foreach my $freq (@freqs) {
	system("echo $freq > $hwmon_dev/$freq_file");
	sleep(1);
	print "freq = $freq\n";
	print CSV ($freq >= 1000 ? ($freq/1000)." kHz" : $freq." Hz");

	for (my $pwm = 248; $pwm; $pwm -= 8) {
		system("echo $pwm > $hwmon_dev/$pwm_file");
		sleep(SLEEP);
		my $fan1 = read_value("$hwmon_dev/$fan_file");
		sleep(1);
		my $fan2 = read_value("$hwmon_dev/$fan_file");
		sleep(1);
		my $fan3 = read_value("$hwmon_dev/$fan_file");
		print CSV ";".int(($fan1+$fan2+$fan3)/3);
	}
	print CSV "\n";
	system("echo 255 > $hwmon_dev/$pwm_file");
}

close(CSV);
system("echo 255 > $hwmon_dev/$pwm_file");