Bluetooth: Controller: Central maximum data PDU size time spacing

Use the maximum data PDU size time reservation space
considering the Data length could be updated from default
27 bytes to maximum support size.

If maximum time reservation is disabled then time space
reservation corresponding to the default data length at the
time of the start/enable of Central role is used.

Note, currently this value is only used to space multiple central
connections and not for actual ticker time reservations.

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

Author: cvinayak

subsys/bluetooth/controller/Kconfig.ll_sw_split

@@ -436,20 +436,40 @@ config BT_CTLR_SCHED_ADVANCED_CENTRAL_CONN_SPACING
 	depends on BT_CTLR_SCHED_ADVANCED
 	default 0
 	help
-	  The central preferred connection spacing defines an additional spacing
-	  in microseconds, added to the fixed ~1250 us spacing obtained by enabling
-	  BT_CTLR_SCHED_ADVANCED. Specifying 0 (default) will obtain a spacing of
-	  ~1250 us, whereas specifying 1250 will yield a spacing of ~2500 us.
-	  The spacing is defined as the distance in time between the anchor points
-	  of the established central role connections.
-	  The precision is determined by the resolution of the platform dependent
-	  ticker clock.
-	  When specifying values above 6.25 ms, the spacing may be unobtainable if
-	  the connection interval becomes smaller than the total spacing. In that
-	  case, modulo is applied and a total spacing of 15 ms on a 10 ms connection
-	  interval yields 5 ms spacing.
-	  For multiple connections, it may become impossible to honor the preferred
-	  spacing, in which case overlapping will occur.
+	  The preferred connection spacing between multiple simultaneous central
+	  roles in microseconds. The Controller will calculate the required time
+	  reservation using the data length and PHY currently in use. The
+	  greater of the preferred spacing and the calculated time reservation
+	  will be used.
+	  The precision is determined by the resolution of the platform
+	  dependent ticker clock.
+	  The upper range is a ceil value permitting any tuning of Controller's
+	  radio handling overheads and to allow Coded PHY S8 coding scheme PDU
+	  time, i.e. radio event overheads + 17040 (PDU Tx) + 150 (tIFS) + 4
+	  (active clock jitter) + 17040 (PDU rx) = (radio event overheads +
+	  34234) microseconds.
+
+config BT_CTLR_CENTRAL_RESERVE_MAX
+	bool "Use maximum data PDU size time reservation for Central"
+	depends on BT_CENTRAL
+	default y
+	help
+	  Use the maximum data PDU size time reservation considering the Data
+	  length could be updated from default 27 bytes to maximum support size.
+	  If maximum time reservation is disabled then time reservation
+	  corresponding to the default data length at the time of the
+	  start/enable of Central role is used.
+
+	  Note, currently this value is only used to space multiple central
+	  connections and not for actual ticker time reservations.
+
+config BT_CTLR_SLOT_RESERVATION_UPDATE
+	bool "Update event length reservation after PHY or DLE update"
+	depends on !BT_LL_SW_LLCP_LEGACY && (BT_CTLR_DATA_LENGTH || BT_CTLR_PHY)
+	default y
+	help
+	  Updates the event length reservation after a completed Data Length Update
+	  and/or PHY Update procedure to avoid overlap of radio events
 
 config BT_CTLR_LLL_PRIO
 	int "Lower Link Layer (Radio) IRQ priority" if (BT_CTLR_ULL_LLL_PRIO_SUPPORT && !BT_CTLR_ZLI)

subsys/bluetooth/controller/ll_sw/ull_sched.c

@@ -4,9 +4,8 @@
  * SPDX-License-Identifier: Apache-2.0
  */
 
-#include <zephyr/kernel.h>
-
 #include <zephyr/sys/byteorder.h>
+#include <zephyr/bluetooth/hci.h>
 
 #include "hal/ccm.h"
 #include "hal/radio.h"
@@ -48,6 +47,7 @@
 #define LOG_MODULE_NAME bt_ctlr_ull_sched
 #include "common/log.h"
 #include "hal/debug.h"
+#include "ll_feat.h"
 
 #if defined(CONFIG_BT_CTLR_CONN_PARAM_REQ)
 #if defined(CONFIG_BT_LL_SW_LLCP_LEGACY)
@@ -876,7 +876,47 @@ static struct ull_hdr *ull_hdr_get_cb(uint8_t ticker_id, uint32_t *ticks_slot)
 
 		conn = ll_conn_get(ticker_id - TICKER_ID_CONN_BASE);
 		if (conn && !conn->lll.role) {
-			*ticks_slot = conn->ull.ticks_slot;
+			uint32_t ticks_slot_conn;
+
+			if (IS_ENABLED(CONFIG_BT_CTLR_CENTRAL_RESERVE_MAX)) {
+				uint32_t ready_delay_us;
+				uint16_t max_tx_time;
+				uint16_t max_rx_time;
+				uint32_t time_us;
+
+#if defined(CONFIG_BT_CTLR_PHY)
+				ready_delay_us =
+					lll_radio_tx_ready_delay_get(conn->lll.phy_tx,
+								     conn->lll.phy_flags);
+#else
+				ready_delay_us =
+					lll_radio_tx_ready_delay_get(0U, 0U);
+#endif
+
+#if defined(CONFIG_BT_CTLR_PHY_CODED)
+				max_tx_time = PDU_DC_MAX_US(LL_LENGTH_OCTETS_TX_MAX,
+							    PHY_CODED);
+				max_rx_time = PDU_DC_MAX_US(LL_LENGTH_OCTETS_RX_MAX,
+							    PHY_CODED);
+#else /* !CONFIG_BT_CTLR_PHY_CODED */
+				max_tx_time = PDU_DC_MAX_US(LL_LENGTH_OCTETS_TX_MAX,
+							    PHY_1M);
+				max_rx_time = PDU_DC_MAX_US(LL_LENGTH_OCTETS_RX_MAX,
+							    PHY_1M);
+#endif /* !CONFIG_BT_CTLR_PHY_CODED */
+
+				time_us = EVENT_OVERHEAD_START_US +
+					  ready_delay_us +  max_rx_time +
+					  EVENT_IFS_US + max_tx_time;
+				ticks_slot_conn =
+					HAL_TICKER_US_TO_TICKS(time_us);
+			} else {
+				ticks_slot_conn = conn->ull.ticks_slot;
+			}
+
+			*ticks_slot = MAX(ticks_slot_conn,
+				    HAL_TICKER_US_TO_TICKS(
+					    CONFIG_BT_CTLR_SCHED_ADVANCED_CENTRAL_CONN_SPACING));
 
 			return &conn->ull;
 		}

tests/bluetooth/bsim_bt/bsim_test_multiple/prj.conf

@@ -43,3 +43,7 @@ CONFIG_BT_CTLR_RX_BUFFERS=6
 # accuracy, current value here is sufficient for 500ppm at 1 second interval.
 CONFIG_BT_CTLR_ADVANCED_FEATURES=y
 CONFIG_BT_CTLR_SCHED_ADVANCED_CENTRAL_CONN_SPACING=1000
+
+# Do not use max data PDU size time reservation for connection events spacing
+# instead use lesser value as supplied in CONFIG_BT_CTLR_CENTRAL_SPACING
+CONFIG_BT_CTLR_CENTRAL_RESERVE_MAX=n