fixeria has uploaded this change for review.
osmo-bts-trx: reset BTS GSM time on clock (re)start
trx_sched_clock_started() is called when the transceiver is powered
on, e.g. after an A-bis link re-establishment, which in ttcn3-bts-test
happens once per testcase. The transceiver restarts its TDMA frame
number from ~0, but we only reset the per-TRX clock state (tcs),
leaving bts->gsm_time.fn at the previous epoch's value.
As a result the first (low) FN reported by the transceiver is mistaken
for a huge backwards jump, e.g.:
l1sap.c:628 Invalid condition detected: Frame difference is 102-10386=2705364 > 1!
Reset bts->gsm_time to FN 0 here so each clock epoch starts clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Change-Id: Id8da126e460d3846a3be5bdb271553457fdd0590
---
M src/osmo-bts-trx/scheduler_trx.c
1 file changed, 6 insertions(+), 0 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-bts refs/changes/50/42850/1
diff --git a/src/osmo-bts-trx/scheduler_trx.c b/src/osmo-bts-trx/scheduler_trx.c
index 770a54b..d791eaf 100644
--- a/src/osmo-bts-trx/scheduler_trx.c
+++ b/src/osmo-bts-trx/scheduler_trx.c
@@ -491,6 +491,12 @@
osmo_fd_close(&tcs->fn_timer_ofd);
memset(tcs, 0, sizeof(*tcs));
tcs->fn_timer_ofd.fd = -1;
+ /* This is a fresh clock epoch: the transceiver was (re)powered on, e.g. due to
+ * A-bis link (re-)establishment, and (re)starts its TDMA frame number from 0.
+ * Reset our notion of GSM time accordingly, so that the first CLCK.ind reported
+ * by the transceiver is not mistaken for a huge backwards jump against a stale
+ * frame number left over from the previous epoch. */
+ gsm_fn2gsmtime(&bts->gsm_time, 0);
/* Set up timeout to shutdown BTS if no clock ind is received in a few
* seconds. Upon clock ind receival, fn_timer_ofd will be reused and
* timeout won't trigger.
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