nimble/ll: Fix calculations for aux scheduling
We need to take scheduling offset into account when calculating
advertising event duration.
@@ -1674,28 +1674,18 @@ ble_ll_adv_aux_set_start_time(struct ble_ll_adv_sm *advsm)
chans = bits[advsm->adv_chanmask];
- /*
- * We want to schedule auxiliary packet as soon as possible after the end
- * of advertising event, but no sooner than T_MAFS. The interval between
- * advertising packets is 250 usecs (8.19 ticks) on LE Coded and a bit less
- * on 1M, but it can vary a bit due to scheduling which we can't really
- * control. Since we round ticks up for both interval and T_MAFS, we still
- * have some margin here. The worst thing that can happen is that we skip
- * last advertising packet which is not a bit problem so leave it as-is, no
- * need to make code more complicated.
- */
-
- /*
- * XXX: this could be improved if phy has TX-TX transition with controlled
- * or predefined interval, but since it makes advertising code even
- * more complicated let's skip it for now...
- */
-
adv_pdu_dur = (int32_t)(sched->end_time - sched->start_time) -
g_ble_ll_sched_offset_ticks;
- /* 9 is 8.19 ticks rounded up - see comment above */
- adv_event_dur = (adv_pdu_dur * chans) + (9 * (chans - 1));
+ /* The interval between advertising PDUs may vary due to scheduling, but in
+ * general we reserve 3 ticks for end-to-schedule time and add scheduler
+ * offset. That should be more that enough to make sure there's at least
+ * T_mafs delay between last advertising PDU and auxiliary PDU.
+ *
+ * TODO we can make this much more efficient with TX-TX transition
+ */
+ adv_event_dur = (adv_pdu_dur * chans) +
+ ((3 + g_ble_ll_sched_offset_ticks) * (chans - 1));
advsm->aux[0].start_time = advsm->adv_event_start_time + adv_event_dur +
ble_ll_tmr_u2t_up(BLE_LL_MAFS +
