Bluetooth: controller: Enable CIS establishment in same ACL instant

If CIS offset in LL_CIS_IND is less than EVENT_OVERHEAD_START_US, the
controller is not able to establish the CIS in the ACL connection event
specified, but needs to start setup one connection event earlier.

With this commit, if offset is larger than EVENT_OVERHEAD_START_US the
first CIS event can be prepared in due time immediately.

This enables the controller to setup first CIS, even when instant is
equal to the ACL event_counter.

Signed-off-by: Morten Priess <[email protected]>

Author: mtpr-ot

subsys/bluetooth/controller/ll_sw/isoal.c

@@ -113,7 +113,7 @@ isoal_status_t isoal_reset(void)
  * @param  time_diff Time difference (signed)
  * @return           Wrapped time after difference
  */
-static uint32_t isoal_get_wrapped_time_us(uint32_t time_now_us, int32_t time_diff_us)
+uint32_t isoal_get_wrapped_time_us(uint32_t time_now_us, int32_t time_diff_us)
 {
 	LL_ASSERT(time_now_us <= ISOAL_TIME_WRAPPING_POINT_US);
 

subsys/bluetooth/controller/ll_sw/isoal.h

@@ -419,6 +419,8 @@ struct isoal_source {
 	uint64_t context_active:1;
 };
 
+uint32_t isoal_get_wrapped_time_us(uint32_t time_now_us, int32_t time_diff_us);
+
 isoal_status_t isoal_init(void);
 
 isoal_status_t isoal_reset(void);

subsys/bluetooth/controller/ll_sw/ull_conn_iso.c

@@ -844,17 +844,25 @@ void ull_conn_iso_start(struct ll_conn *conn, uint32_t ticks_at_expire,
 		ticks_remainder = EVENT_US_FRAC_TO_REMAINDER(iso_interval_us_frac);
 
 #if defined(CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START)
-		if (instant_latency == 0U) {
-			/* Adjust CIG offset and reference point ahead one
-			 * interval
-			 */
-			cig_offset_us += conn->lll.interval * CONN_INT_UNIT_US;
-			cig->cig_ref_point += conn->lll.interval *
-					      CONN_INT_UNIT_US;
+		bool early_start = (cis->offset < EVENT_OVERHEAD_START_US);
+
+		if (early_start) {
+			if (instant_latency == 0U) {
+				/* Adjust CIG offset and reference point ahead one
+				 * interval
+				 */
+				cig_offset_us += (conn->lll.interval * CONN_INT_UNIT_US);
+				cig->cig_ref_point = isoal_get_wrapped_time_us(cig->cig_ref_point,
+							conn->lll.interval * CONN_INT_UNIT_US);
+			} else {
+				LL_ASSERT(instant_latency == 1U);
+			}
 		} else {
-			LL_ASSERT(instant_latency == 1U);
+			/* FIXME: Handle latency due to skipped ACL events around the
+			 * instant to start CIG
+			 */
+			LL_ASSERT(instant_latency == 0U);
 		}
-
 #else /* CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START */
 		/* FIXME: Handle latency due to skipped ACL events around the
 		 * instant to start CIG

subsys/bluetooth/controller/ll_sw/ull_llcp_cc.c

@@ -404,7 +404,8 @@ static void rp_cc_state_wait_rx_cis_ind(struct ll_conn *conn, struct proc_ctx *c
 	case RP_CC_EVT_CIS_IND:
 		llcp_pdu_decode_cis_ind(ctx, pdu);
 		if (!ull_peripheral_iso_setup(&pdu->llctrl.cis_ind, ctx->data.cis_create.cig_id,
-					      ctx->data.cis_create.cis_handle)) {
+					      ctx->data.cis_create.cis_handle,
+					      &ctx->data.cis_create.conn_event_count)) {
 
 			/* CIS has been setup, go wait for 'instant' before starting */
 			ctx->state = RP_CC_STATE_WAIT_INSTANT;
@@ -456,29 +457,14 @@ static void rp_cc_check_instant(struct ll_conn *conn, struct proc_ctx *ctx, uint
 				void *param)
 {
 	uint16_t start_event_count;
-	uint16_t instant_latency;
 	uint16_t event_counter;
 
 	event_counter = ull_conn_event_counter(conn);
 	start_event_count = ctx->data.cis_create.conn_event_count;
 
-#if defined(CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START)
-	struct ll_conn_iso_group *cig;
-
-	cig = ll_conn_iso_group_get_by_id(ctx->data.cis_create.cig_id);
-	LL_ASSERT(cig);
-
-	if (!cig->started) {
-		/* Start ISO peripheral one event before the requested instant
-		 * for first CIS. This is done to be able to accept small CIS
-		 * offsets.
-		 */
-		start_event_count--;
-	}
-#endif /* CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START */
+	if (is_instant_reached_or_passed(start_event_count, event_counter)) {
+		uint16_t instant_latency = (event_counter - start_event_count) & 0xffff;
 
-	instant_latency = (event_counter - start_event_count) & 0xffff;
-	if (instant_latency <= 0x7fff) {
 		/* Start CIS */
 		ull_conn_iso_start(conn, conn->llcp.prep.ticks_at_expire,
 				   ctx->data.cis_create.cis_handle,

subsys/bluetooth/controller/ll_sw/ull_peripheral_iso.c

@@ -286,10 +286,12 @@ uint8_t ull_peripheral_iso_acquire(struct ll_conn *acl,
 }
 
 uint8_t ull_peripheral_iso_setup(struct pdu_data_llctrl_cis_ind *ind,
-				 uint8_t cig_id, uint16_t cis_handle)
+				 uint8_t cig_id, uint16_t cis_handle,
+				 uint16_t *conn_event_count)
 {
 	struct ll_conn_iso_stream *cis = NULL;
 	struct ll_conn_iso_group *cig;
+	uint32_t cis_offset;
 
 	/* Get CIG by id */
 	cig = ll_conn_iso_group_get_by_id(cig_id);
@@ -305,8 +307,22 @@ uint8_t ull_peripheral_iso_setup(struct pdu_data_llctrl_cis_ind *ind,
 		return BT_HCI_ERR_UNSPECIFIED;
 	}
 
+	cis_offset = sys_get_le24(ind->cis_offset);
+
+#if defined(CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START)
+	if (!cig->started) {
+		/* This is the first CIS. Make sure we can make the anchorpoint, otherwise
+		 * we need to move up the instant up by one connection interval.
+		 */
+		if (cis_offset < EVENT_OVERHEAD_START_US) {
+			/* Start one connection event earlier */
+			(*conn_event_count)--;
+		}
+	}
+#endif /* CONFIG_BT_CTLR_PERIPHERAL_ISO_EARLY_CIG_START */
+
 	cis->sync_delay = sys_get_le24(ind->cis_sync_delay);
-	cis->offset = sys_get_le24(ind->cis_offset);
+	cis->offset = cis_offset;
 	memcpy(cis->lll.access_addr, ind->aa, sizeof(ind->aa));
 	cis->lll.event_count = -1;
 	cis->lll.next_subevent = 0U;

subsys/bluetooth/controller/ll_sw/ull_peripheral_iso_internal.h

@@ -14,7 +14,8 @@ uint8_t ull_peripheral_iso_acquire(struct ll_conn *acl,
 				   uint16_t *cis_handle);
 uint8_t ull_peripheral_iso_setup(struct pdu_data_llctrl_cis_ind *ind,
 				 uint8_t cig_id,
-				 uint16_t cis_handle);
+				 uint16_t cis_handle,
+				 uint16_t *conn_event_count);
 void ull_peripheral_iso_update_peer_sca(struct ll_conn *acl);
 void ull_peripheral_iso_update_ticker(struct ll_conn_iso_group *cig,
 				      uint32_t ticks_at_expire,