client/site_tests/power_Standby/power_Standby.py

# Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import logging, math, time

from autotest_lib.client.bin import test
from autotest_lib.client.common_lib import error
from autotest_lib.client.cros import power_status, rtc, sys_power

class power_Standby(test.test):
    """Measure Standby(S3) power test."""
    version = 1
    _percent_min_charge = 0.1
    _min_sample_hours = 0.1

    def run_once(self, test_hours=None, sample_hours=None,
                 percent_initial_charge_min=0.2, max_milliwatts_standby=None):

        if test_hours <= sample_hours:
            raise error.TestFail("Test hours must be greater than sample hours")

        # If we're measuring <= 6min of S3 then the S0 time is not negligible.
        # Note, reasonable rule of thumb is S0 idle is ~10-20 times S3 power.
        if sample_hours < self._min_sample_hours:
            raise error.TestFail("Must suspend more than %.2f hours" % \
                                 sample_hours)

        # Query initial power status
        power_stats = power_status.get_status()
        power_stats.assert_battery_state(percent_initial_charge_min)
        charge_avail = power_stats.battery[0].charge_now

        max_hours = charge_avail * power_stats.battery[0].voltage_min_design / \
            (max_milliwatts_standby / 1000)
        if max_hours < test_hours:
            raise error.TestFail('Battery not charged adequately for test')

        elapsed_hours = 0

        while elapsed_hours < test_hours:
            charge_before = power_stats.battery[0].charge_now
            # Set RTC for wakeup
            before_suspend_secs = rtc.get_seconds()
            alarm_secs =  before_suspend_secs + int(sample_hours * 3600)

            # flush RTC as it may not work subsequently if wake was not RTC
            rtc.set_wake_alarm(0)

            rtc.set_wake_alarm(alarm_secs)

            sys_power.suspend_to_ram()

            after_suspend_secs = rtc.get_seconds()

            power_stats.refresh()
            if power_stats.percent_current_charge() < self._percent_min_charge:
                logging.warn("Battery percent = %.2f%%.  Too low to continue")
                break

            # check that the RTC slept the correct amount of time as there could
            # potentially be another wake source that would spoil the test.
            actual_hours = (after_suspend_secs - before_suspend_secs) / 3600.0
            logging.debug("actual_hours = %.4f", actual_hours)
            percent_diff = math.fabs((actual_hours - sample_hours) /
                                     ((actual_hours + sample_hours) / 2) * 100)
            if percent_diff > 2:
                err_str = "Requested S3 time and actual varied by %.2f%%." \
                    % percent_diff
                raise error.TestFail(err_str)

            # Check resulting charge consumption
            charge_used = charge_before - power_stats.battery[0].charge_now
            logging.debug("charge_used = %.6f", charge_used)

            elapsed_hours += actual_hours
            logging.debug("elapsed_hours = %.4f", elapsed_hours)


        charge_used = charge_avail - power_stats.battery[0].charge_now
        if charge_used <= 0:
            raise error.TestFail("Charge used reading is suspect.")
        standby_hours = power_stats.battery[0].charge_full_design / \
            charge_used * elapsed_hours
        energy_used = charge_used * power_stats.battery[0].voltage_min_design
        standby_milliwatts = energy_used / standby_hours * 1000

        results = {}
        results['milliwatts_standby_power'] = standby_milliwatts
        results['hours_standby_time'] = standby_hours
        self.write_perf_keyval(results)

        # need to sleep for some time to allow network connection to return
        time.sleep(10)