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Bluetooth: Controller: Fix periodic sync Skip value vs Sync_Timeout

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Adjust skip value so that there is minimum of 6 events that can be
listened to before Sync_Timeout occurs.

Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>
This commit is contained in:
Vinayak Kariappa Chettimada 2022-11-23 14:06:13 +05:30 • committed by Carles Cufí
commit 668505e778
1 changed files with 20 additions and 0 deletions
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20
subsys/bluetooth/controller/ll_sw/ull_sync.c
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@ -719,6 +719,26 @@ void ull_sync_setup(struct ll_scan_set *scan, struct ll_scan_aux_set *aux,
sync->timeout_reload = RADIO_SYNC_EVENTS((sync->timeout * 10U *
USEC_PER_MSEC), interval_us);
/* Adjust Skip value so that there is minimum of 6 events that can be
* listened to before Sync_Timeout occurs.
* The adjustment of the skip value is controller implementation
* specific and not specified by the Bluetooth Core Specification v5.3.
* The Controller `may` use the Skip value, and the implementation here
* covers a case where Skip value could lead to less events being
* listened to until Sync_Timeout. Listening to more consecutive events
* before Sync_Timeout increases probability of retaining the Periodic
* Synchronization.
*/
if (sync->timeout_reload > CONN_ESTAB_COUNTDOWN) {
uint16_t skip_max = sync->timeout_reload - CONN_ESTAB_COUNTDOWN;
if (sync->skip > skip_max) {
sync->skip = skip_max;
}
} else {
sync->skip = 0U;
}
sync->sync_expire = CONN_ESTAB_COUNTDOWN;
/* Extract the SCA value from the sca_chm field of the sync_info