Bluetooth: controller: fix time-wrapping of cig_ref_point

Time wrapping was omitted at some points. These were corrected or clarified. Signed-off-by: Nirosharn Amarasinghe <[email protected]>
zephyrproject-rtos · Jun 6, 2023 · 40dde5b · 40dde5b
1 parent f043425
commit 40dde5b
Show file tree

Hide file tree

Showing 2 changed files with 13 additions and 6 deletions.
diff --git a/subsys/bluetooth/controller/ll_sw/ull_central_iso.c b/subsys/bluetooth/controller/ll_sw/ull_central_iso.c
@@ -761,11 +761,18 @@ uint8_t ull_central_iso_setup(uint16_t cis_handle,
 
 		/* CIG is started. Use the CIG reference point and latest ticks_at_expire
 		 * for associated ACL, to calculate the offset.
+		 * NOTE: The following calculations are done in a 32-bit time
+		 * range with full consideration and expectation that the
+		 * controller clock does not support the full 32-bit range in
+		 * microseconds. However it is valid as the purpose is to
+		 * calculate the difference and the spare higher order bits will
+		 * ensure that no wrapping can occur before the termination
+		 * condition of the while loop is met. Using time wrapping will
+		 * complicate this.
 		 */
-		time_of_intant = isoal_get_wrapped_time_us(
-			HAL_TICKER_TICKS_TO_US(conn->llcp.prep.ticks_at_expire),
-			EVENT_OVERHEAD_START_US +
-			(instant - event_counter) * conn->lll.interval * CONN_INT_UNIT_US);
+		time_of_intant = HAL_TICKER_TICKS_TO_US(conn->llcp.prep.ticks_at_expire) +
+				EVENT_OVERHEAD_START_US +
+				((instant - event_counter) * conn->lll.interval * CONN_INT_UNIT_US);
 
 		cig_ref_point = cig->cig_ref_point;
 		while (cig_ref_point < time_of_intant) {

diff --git a/subsys/bluetooth/controller/ll_sw/ull_iso.c b/subsys/bluetooth/controller/ll_sw/ull_iso.c
@@ -1410,8 +1410,8 @@ static void iso_rx_cig_ref_point_update(struct ll_conn_iso_group *cig,
 			/* Update the CIG reference point based on the CIS
 			 * anchor point
 			 */
-			cig->cig_ref_point = meta->timestamp + cis_sync_delay -
-					     cig_sync_delay;
+			cig->cig_ref_point = isoal_get_wrapped_time_us(meta->timestamp,
+						cis_sync_delay - cig_sync_delay);
 		}
 	}
 }