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hwclock: drop all samples on reset

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On some HW it seems it's possible to get an occasional bad reading of
the PHC (with normal delay), or in a worse case the clock can step due
to a HW/driver bug, which triggers reset of the HW clock instance. To
avoid having a bad estimate of the frequency when the next (good) sample
is accumulated, drop also the last sample which triggered the reset.
This commit is contained in:
Miroslav Lichvar 2017-08-22 13:13:45 +02:00
parent 27cbf20d23
commit 6dad2c24bf
2 changed files with 6 additions and 6 deletions
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10
hwclock.c
View file

@ -174,12 +174,12 @@ HCL_AccumulateSample(HCL_Instance clock, struct timespec *hw_ts,
/* Drop unneeded samples */
clock->n_samples -= best_start;
/* If the fit doesn't cross the error interval of the last sample, throw away
all previous samples and keep only the frequency estimate */
/* If the fit doesn't cross the error interval of the last sample,
throw away all samples and start again */
if (fabs(clock->offset) > err) {
DEBUG_LOG("HW clock reset offset=%e", clock->offset);
clock->offset = 0.0;
clock->n_samples = 1;
DEBUG_LOG("HW clock reset");
clock->n_samples = 0;
clock->valid_coefs = 0;
}
DEBUG_LOG("HW clock samples=%d offset=%e freq=%.9e raw_freq=%.9e err=%e ref_diff=%e",

2
test/unit/hwclock.c
View file

@ -65,7 +65,7 @@ test_unit(void)
if (HCL_NeedsNewSample(clock, &local_ts))
HCL_AccumulateSample(clock, &hw_ts, &local_ts, 2.0 * jitter);
TEST_CHECK(j < 20 || clock->valid_coefs);
TEST_CHECK(clock->valid_coefs || clock->n_samples < 2);
if (!clock->valid_coefs)
continue;