Bluetooth: Controller: Fix Central CIS SN/NESN for skipped events

Fix Central CIS SN and NESN for skipped events during CIS
setup. It is possible that CIG event may overlap the ACL or
other events at the CIS create instant, and hence have non
zero lazy value during the CIS setup events until CIS is
established.

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

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

@@ -179,9 +179,19 @@ static int prepare_cb(struct lll_prepare_param *p)
 	cig_lll->latency_prepare = 0U;
 
 	/* Adjust the SN and NESN for skipped CIG events */
-	/* sn and nesn are 1-bit, only Least Significant bit is needed */
-	cis_lll->sn += cis_lll->tx.bn * lazy;
-	cis_lll->nesn += cis_lll->rx.bn * lazy;
+	if (cis_lll->event_count) {
+		uint16_t cis_lazy;
+
+		if (lazy > cis_lll->event_count) {
+			cis_lazy = lazy - cis_lll->event_count;
+		} else {
+			cis_lazy = lazy;
+		}
+
+		/* sn and nesn are 1-bit, only Least Significant bit is needed */
+		cis_lll->sn += cis_lll->tx.bn * cis_lazy;
+		cis_lll->nesn += cis_lll->rx.bn * cis_lazy;
+	}
 
 	se_curr = 1U;
 	bn_tx = 1U;
@@ -368,9 +378,19 @@ static int prepare_cb(struct lll_prepare_param *p)
 	do {
 		cis_lll = ull_conn_iso_lll_stream_get_by_group(cig_lll, &cis_handle);
 		if (cis_lll && cis_lll->active) {
-			/* sn and nesn are 1-bit, only Least Significant bit is needed */
-			cis_lll->sn += cis_lll->tx.bn * lazy;
-			cis_lll->nesn += cis_lll->rx.bn * lazy;
+			if (cis_lll->event_count) {
+				uint16_t cis_lazy;
+
+				if (lazy > cis_lll->event_count) {
+					cis_lazy = lazy - cis_lll->event_count;
+				} else {
+					cis_lazy = lazy;
+				}
+
+				/* sn and nesn are 1-bit, only Least Significant bit is needed */
+				cis_lll->sn += cis_lll->tx.bn * cis_lazy;
+				cis_lll->nesn += cis_lll->rx.bn * cis_lazy;
+			}
 		}
 	} while (cis_lll);