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test: timer: behavior: Enhancement for running this test

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Zephyr timer is based on system ticks, there usually exists some time drift
due to round up/down errors between cycles, ticks and time delay, we
need to add those expected time drift into the bound calculation for
running this test.
Add a new config TIMER_TEST_PERIOD_MAX_DRIFT_PERCENT for users to set
expected maximum drift percentage for the timer period.

Signed-off-by: Chen Peng1 <peng1.chen@intel.com>
This commit is contained in:
Chen Peng1 2022-09-19 15:02:17 +08:00 • committed by Fabio Baltieri
commit 02f5e14b65
2 changed files with 37 additions and 11 deletions
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6
tests/kernel/timer/timer_behavior/Kconfig
View file

@ -20,3 +20,9 @@ config TIMER_TEST_MAX_STDDEV
config TIMER_TEST_MAX_DRIFT
int "Maximum drift in microseconds allowed (should be about 1 period allowance)"
default 1000
config TIMER_TEST_PERIOD_MAX_DRIFT_PERCENT
int "Maximum drift percentage for the timer period"
default 10
help
A value of 10 means 10%.

42
tests/kernel/timer/timer_behavior/src/main.c
View file

@ -133,17 +133,30 @@ ZTEST(timer_behavior, test_periodic_behavior)
double expected_time_us =
(double)CONFIG_TIMER_TEST_PERIOD * (double)CONFIG_TIMER_TEST_SAMPLES;
double actual_time_us = cycles_to_us((double)periodic_end - (double)periodic_start);
double time_diff_us = actual_time_us - expected_time_us;
/* While this could be non-integer, the mean should be very close to it over time */
double expected_period =
((double)CONFIG_TIMER_TEST_PERIOD * (double)CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC) /
1000000.0;
/*
* Expected period drift(us) due to round up/down errors during the
* conversion between ticks, cycles and delay.
*/
k_timeout_t actual_timeout = K_USEC(CONFIG_TIMER_TEST_PERIOD);
uint64_t cyc_per_tick = CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC
/ CONFIG_SYS_CLOCK_TICKS_PER_SEC;
double expected_period_drift = ((double)actual_timeout.ticks * cyc_per_tick
- expected_period) / CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC * 1000000;
double expected_time_drift_us = expected_period_drift
* CONFIG_TIMER_TEST_SAMPLES;
double time_diff_us = actual_time_us - expected_time_us
- expected_time_drift_us;
TC_PRINT("timer clock rate %d, kernel tick rate %d, expected period %d us, samples %d, "
"period %f cycles\n",
CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC, CONFIG_SYS_CLOCK_TICKS_PER_SEC,
CONFIG_TIMER_TEST_PERIOD, CONFIG_TIMER_TEST_SAMPLES, expected_period);
"period %f cycles, expected period drift %f us\n",
CONFIG_SYS_CLOCK_HW_CYCLES_PER_SEC, CONFIG_SYS_CLOCK_TICKS_PER_SEC,
CONFIG_TIMER_TEST_PERIOD, CONFIG_TIMER_TEST_SAMPLES, expected_period,
expected_period_drift);
TC_PRINT("statistics samples %d, rollovers %u, mean %f us, variance %f us, stddev %f us, "
"min %f us, max %f us\n",
CONFIG_TIMER_TEST_SAMPLES - periodic_rollovers, periodic_rollovers, mean_us,
@ -152,19 +165,26 @@ ZTEST(timer_behavior, test_periodic_behavior)
"%f cycles, min %llu cycles, max %llu cycles\n",
CONFIG_TIMER_TEST_SAMPLES - periodic_rollovers, periodic_rollovers, mean_cyc,
variance_cyc, stddev_cyc, min_cyc, max_cyc);
TC_PRINT("timer start cycle %llu, end cycle %llu, total time %f, expected time %f, "
"difference %f\n",
periodic_start, periodic_end, actual_time_us, expected_time_us, time_diff_us);
TC_PRINT("timer start cycle %llu, end cycle %llu, total time %f, "
"expected time %f, expected time drift %f, difference %f\n",
periodic_start, periodic_end, actual_time_us, expected_time_us,
expected_time_drift_us, time_diff_us);
/* Validate the maximum/minimum timer period is off by no more than 10% */
double test_period = (double)CONFIG_TIMER_TEST_PERIOD;
double min_us_bound = test_period - 0.10 * test_period;
double max_us_bound = test_period + 0.10 * test_period;
double period_max_drift_percentage =
(double)CONFIG_TIMER_TEST_PERIOD_MAX_DRIFT_PERCENT / 100;
double min_us_bound = test_period - period_max_drift_percentage * test_period
+ expected_period_drift;
double max_us_bound = test_period + period_max_drift_percentage * test_period
+ expected_period_drift;
zassert_true(min_us >= min_us_bound,
"Shortest timer period too short (off by more than 10%)");
"Shortest timer period too short (off by more than expected %d%)",
CONFIG_TIMER_TEST_PERIOD_MAX_DRIFT_PERCENT);
zassert_true(max_us <= max_us_bound,
"Longest timer period too long (off by more than 10%)");
"Longest timer period too long (off by more than expected %d%)",
CONFIG_TIMER_TEST_PERIOD_MAX_DRIFT_PERCENT);
/* Validate the timer deviation (precision/jitter of the timer) is within a configurable
* bound