Bluetooth: Controller: Fix BT_CTLR_SCAN_AUX_SYNC_RESERVE_MIN

Fix BT_CTLR_SCAN_AUX_SYNC_RESERVE_MIN such that event is not
aborted when near supervision timeout conditions.

Relates to commit ddf0499 ("Bluetooth: Controller: Add
abort fairness in overlapping Periodic Sync").

Signed-off-by: Vinayak Kariappa Chettimada <[email protected]>

Author: cvinayak

subsys/bluetooth/controller/ll_sw/lll_sync.h

@@ -27,6 +27,7 @@ struct lll_sync {
 	uint8_t filter_policy:1;
 	uint8_t is_rx_enabled:1;
 	uint8_t is_aux_sched:1;
+	uint8_t forced:1;
 
 #if defined(CONFIG_BT_CTLR_SYNC_ISO)
 	uint8_t sca:3;

subsys/bluetooth/controller/ll_sw/nordic/lll/lll_sync.c

@@ -562,6 +562,13 @@ static int is_abort_cb(void *next, void *curr, lll_prepare_cb_t *resume_cb)
 
 		lll_sync_next = ull_sync_lll_is_valid_get(next);
 		if (!lll_sync_next) {
+			lll_sync_curr = curr;
+
+			/* Do not abort if near supervision timeout */
+			if (lll_sync_curr->forced) {
+				return 0;
+			}
+
 			/* Abort current event as next event is not a
 			 * scan and not a scan aux event.
 			 */

subsys/bluetooth/controller/ll_sw/ull_sync.c

@@ -722,6 +722,7 @@ void ull_sync_setup(struct ll_scan_set *scan, struct ll_scan_aux_set *aux,
 	memcpy(lll->crc_init, si->crc_init, sizeof(lll->crc_init));
 	lll->event_counter = sys_le16_to_cpu(si->evt_cntr);
 	lll->phy = aux->lll.phy;
+	lll->forced = 0U;
 
 	interval = sys_le16_to_cpu(si->interval);
 	interval_us = interval * PERIODIC_INT_UNIT_US;
@@ -1020,6 +1021,7 @@ void ull_sync_done(struct node_rx_event_done *done)
 	struct ll_sync_set *sync;
 	uint16_t elapsed_event;
 	uint16_t skip_event;
+	uint8_t force_lll;
 	uint16_t lazy;
 	uint8_t force;
 
@@ -1100,14 +1102,19 @@ void ull_sync_done(struct node_rx_event_done *done)
 
 		/* check timeout */
 		force = 0U;
+		force_lll = 0U;
 		if (sync->timeout_expire) {
 			if (sync->timeout_expire > elapsed_event) {
 				sync->timeout_expire -= elapsed_event;
 
 				/* break skip */
 				lll->skip_event = 0U;
 
-				if (skip_event) {
+				if (sync->timeout_expire <= 6U) {
+					force_lll = 1U;
+
+					force = 1U;
+				} else if (skip_event) {
 					force = 1U;
 				}
 			} else {
@@ -1117,6 +1124,8 @@ void ull_sync_done(struct node_rx_event_done *done)
 			}
 		}
 
+		lll->forced = force_lll;
+
 		/* Check if skip needs update */
 		lazy = 0U;
 		if ((force) || (skip_event != lll->skip_event)) {