test/timer_calib.py

# Copyright 2011 The ChromiumOS Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
#
# Check timers behavior
#

import time


def one_pass(helper):
    helper.wait_output("=== Timer calibration ===")
    res = helper.wait_output(
        "back-to-back get_time : (?P<lat>[0-9]+) us", use_re=True
    )["lat"]
    minlat = int(res)
    helper.trace("get_time latency %d us\n" % minlat)

    helper.wait_output("sleep 1s")
    t0 = time.time()
    second = helper.wait_output(
        "done. delay = (?P<second>[0-9]+) us", use_re=True
    )["second"]
    t1 = time.time()
    secondreal = t1 - t0
    secondlat = int(second) - 1000000
    helper.trace(
        "1s timer latency %d us / real time %f s\n" % (secondlat, secondreal)
    )

    us = {}
    for pow2 in range(7):
        delay = 1 << (7 - pow2)
        us[delay] = helper.wait_output(
            "%d us => (?P<us>[0-9]+) us" % delay, use_re=True
        )["us"]
    helper.wait_output("Done.")

    return minlat, secondlat, secondreal


def test(helper):
    one_pass(helper)

    helper.ec_command("reboot")
    helper.wait_output("--- UART initialized")

    # get the timing results on the second pass
    # to avoid binary translation overhead
    minlat, secondlat, secondreal = one_pass(helper)

    # check that the timings somewhat make sense
    if minlat > 220 or secondlat > 500 or abs(secondreal - 1.0) > 0.200:
        helper.fail(
            "imprecise timings "
            + "(get_time %d us sleep %d us / real time %.3f s)"
            % (minlat, secondlat, secondreal)
        )

    return True  # PASS !