Bluetooth: Controller: BT_CTLR_ISO_TX_BUFFER_SIZE from BT_ISO_TX_MTU

Derive BT_CTLR_ISO_TX_BUFFER_SIZE from BT_ISO_TX_MTU to have optimal Controller memory allocations. BT_CTLR_ISO_TX_BUFFER_SIZE can be set lower than BT_ISO_TX_MTU in which case upper layer can send fragmented SDU to the Controller. Signed-off-by: Vinayak Kariappa Chettimada <vich@nordicsemi.no>
zephyrproject-rtos · May 10, 2024 · 2c6306d · 2c6306d
1 parent 3997479
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Showing 31 changed files with 136 additions and 86 deletions.
diff --git a/samples/bluetooth/broadcast_audio_source/overlay-bt_ll_sw_split.conf b/samples/bluetooth/broadcast_audio_source/overlay-bt_ll_sw_split.conf
@@ -14,11 +14,7 @@ CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=155
 CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
-# FIXME: Host needs CONFIG_BT_ISO_TX_MTU + 4 bytes for sequence number, and  optionally
-# additional + 4 bytes for timestamp when not using BT_ISO_TIMESTAMP_NONE in bt_iso_chan_send(),
-# otherwise Host tries to fragment ISO data.
-# When Host is fixed, CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE can inherit the
-# CONFIG_BT_ISO_TX_MTU value.
-#
-# Supports the highest SDU size required by any BAP LC3 presets (155)
+# Support the highest SDU size required by any BAP LC3 presets (155) + 8 bytes of HCI ISO Data
+# packet overhead (the Packet_Sequence_Number, ISO_SDU_Length, Packet_Status_Flag fields; and
+# the optional Time_Stamp field, if supplied)
 CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=163
diff --git a/samples/bluetooth/central_iso/overlay-bt_ll_sw_split.conf b/samples/bluetooth/central_iso/overlay-bt_ll_sw_split.conf
@@ -0,0 +1,33 @@
+# Zephyr Bluetooth Controller
+CONFIG_BT_LL_SW_SPLIT=y
+
+# Zephyr Bluetooth LE Controller needs 16 event buffers to generate Extended
+# Advertising Report for receiving the complete 1650 bytes of data
+CONFIG_BT_BUF_EVT_RX_COUNT=16
+
+# Set maximum scan data length for Extended Scanning in Bluetooth LE Controller
+CONFIG_BT_CTLR_SCAN_DATA_LEN_MAX=1650
+
+# Increase Zephyr Bluetooth LE Controller Rx buffer to receive complete chain
+# of PDUs
+CONFIG_BT_CTLR_RX_BUFFERS=9
+
+# Sufficient ISO SDU and PDU length for this sample with ISO_TX_MTU of 247
+CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=247
+CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX=251
+
+# Number of supported streami sources and sinks
+CONFIG_BT_CTLR_ISOAL_SOURCES=2
+CONFIG_BT_CTLR_ISOAL_SINKS=1
+
+# Support the highest SDU size required by this sample 247 + 8 bytes of HCI ISO Data
+# packet overhead (timestamp and HCI ISO Data packet header)
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
+CONFIG_BT_CTLR_ISO_TX_BUFFERS=4
+
+# Use Low Latency Connected ISO policy
+CONFIG_BT_CTLR_ADVANCED_FEATURES=y
+CONFIG_BT_CTLR_CONN_ISO_LOW_LATENCY_POLICY=y
+
+# Use the below if the sample is sending stale packet sequence number
+# CONFIG_BT_CTLR_ISOAL_SN_STRICT=n
diff --git a/samples/bluetooth/central_iso/sample.yaml b/samples/bluetooth/central_iso/sample.yaml
@@ -8,3 +8,14 @@ tests:
     integration_platforms:
       - qemu_x86
     tags: bluetooth
+  sample.bluetooth.central_iso.bt_ll_sw_split:
+    harness: bluetooth
+    platform_allow:
+      - qemu_cortex_m3
+      - qemu_x86
+      - nrf52_bsim
+      - nrf52833dk/nrf52833
+    integration_platforms:
+      - nrf52833dk/nrf52833
+    extra_args: OVERLAY_CONFIG=overlay-bt_ll_sw_split.conf
+    tags: bluetooth
diff --git a/samples/bluetooth/hci_ipc/nrf5340_cpunet_bis-bt_ll_sw_split.conf b/samples/bluetooth/hci_ipc/nrf5340_cpunet_bis-bt_ll_sw_split.conf
@@ -77,7 +77,7 @@ CONFIG_BT_CTLR_LLCP_LOCAL_PROC_CTX_BUF_NUM=6
 CONFIG_BT_CTLR_ADV_EXT=y
 CONFIG_BT_CTLR_ADV_PERIODIC=y
 CONFIG_BT_CTLR_ADV_ISO=y
-CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=251
+CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=247
 CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 
 # ISO Receive Controller
@@ -89,7 +89,7 @@ CONFIG_BT_CTLR_SYNC_ISO_STREAM_MAX=2
 
 # ISO Transmissions
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=8
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=251
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
 # ISO Receptions

diff --git a/samples/bluetooth/hci_ipc/nrf5340_cpunet_cis-bt_ll_sw_split.conf b/samples/bluetooth/hci_ipc/nrf5340_cpunet_cis-bt_ll_sw_split.conf
@@ -77,12 +77,12 @@ CONFIG_BT_CTLR_LLCP_LOCAL_PROC_CTX_BUF_NUM=6
 # ISO Connection Oriented
 CONFIG_BT_CTLR_CENTRAL_ISO=y
 CONFIG_BT_CTLR_PERIPHERAL_ISO=y
-CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=251
+CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=247
 CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX=251
 
 # ISO Transmissions
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=8
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=251
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
 # ISO Receptions

diff --git a/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso-bt_ll_sw_split.conf b/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso-bt_ll_sw_split.conf
@@ -82,7 +82,7 @@ CONFIG_BT_CTLR_LLCP_LOCAL_PROC_CTX_BUF_NUM=6
 CONFIG_BT_CTLR_ADV_EXT=y
 CONFIG_BT_CTLR_ADV_PERIODIC=y
 CONFIG_BT_CTLR_ADV_ISO=y
-CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=251
+CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=247
 CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 
 # ISO Receive Controller
@@ -95,12 +95,12 @@ CONFIG_BT_CTLR_SYNC_ISO_STREAM_MAX=2
 # ISO Connection Oriented
 CONFIG_BT_CTLR_CENTRAL_ISO=y
 CONFIG_BT_CTLR_PERIPHERAL_ISO=y
-CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=251
+CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=247
 CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX=251
 
 # ISO Transmissions
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=8
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=251
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
 # ISO Receptions

diff --git a/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso_broadcast-bt_ll_sw_split.conf b/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso_broadcast-bt_ll_sw_split.conf
@@ -31,8 +31,8 @@ CONFIG_BT_CTLR_ADV_PERIODIC=y
 CONFIG_BT_CTLR_ADV_DATA_LEN_MAX=191
 CONFIG_BT_CTLR_ADV_ISO=y
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=16
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=251
-CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=251
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
+CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=247
 CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 

diff --git a/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso_central-bt_ll_sw_split.conf b/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso_central-bt_ll_sw_split.conf
@@ -44,12 +44,12 @@ CONFIG_BT_CTLR_SCAN_DATA_LEN_MAX=191
 # ISO Connection Oriented
 CONFIG_BT_CTLR_CENTRAL_ISO=y
 CONFIG_BT_CTLR_PERIPHERAL_ISO=n
-CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=251
+CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=247
 CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX=251
 
 # ISO Transmissions
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=16
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=251
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
 # ISO Receptions

diff --git a/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso_peripheral-bt_ll_sw_split.conf b/samples/bluetooth/hci_ipc/nrf5340_cpunet_iso_peripheral-bt_ll_sw_split.conf
@@ -44,12 +44,12 @@ CONFIG_BT_CTLR_ADV_DATA_LEN_MAX=191
 # ISO Connection Oriented
 CONFIG_BT_CTLR_CENTRAL_ISO=n
 CONFIG_BT_CTLR_PERIPHERAL_ISO=y
-CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=251
+CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=247
 CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX=251
 
 # ISO Transmissions
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=16
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=251
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
 # ISO Receptions

diff --git a/samples/bluetooth/hci_uart/overlay-all-bt_ll_sw_split.conf b/samples/bluetooth/hci_uart/overlay-all-bt_ll_sw_split.conf
@@ -80,7 +80,7 @@ CONFIG_BT_CTLR_DF_CONN_CTE_REQ=y
 CONFIG_BT_CTLR_ADV_EXT=y
 CONFIG_BT_CTLR_ADV_PERIODIC=y
 CONFIG_BT_CTLR_ADV_ISO=y
-CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=251
+CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=247
 CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 
 # ISO Receive Controller
@@ -93,12 +93,12 @@ CONFIG_BT_CTLR_SYNC_ISO_STREAM_MAX=2
 # ISO Connection Oriented
 CONFIG_BT_CTLR_CENTRAL_ISO=y
 CONFIG_BT_CTLR_PERIPHERAL_ISO=y
-CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=251
+CONFIG_BT_CTLR_CONN_ISO_SDU_LEN_MAX=247
 CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX=251
 
 # ISO Transmissions
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=8
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=251
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=255
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
 # ISO Receptions

diff --git a/samples/bluetooth/iso_broadcast/overlay-bt_ll_sw_split.conf b/samples/bluetooth/iso_broadcast/overlay-bt_ll_sw_split.conf
@@ -1,13 +1,20 @@
+# Zephyr Bluetooth Controller
+CONFIG_BT_LL_SW_SPLIT=y
+
+# Zephyr Controller tested maximum advertising data that can be set in a single HCI command
+CONFIG_BT_CTLR_ADV_DATA_LEN_MAX=191
+
+# Enable support for Broadcast ISO in Zephyr Bluetooth Controller
 CONFIG_BT_CTLR_ADV_ISO=y
+
+# Sufficient ISO PDU length for this sample
 CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=4
-CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 
+# Number of supported streams
+CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
-# FIXME: Host needs CONFIG_BT_ISO_TX_MTU + 4 bytes for sequence number, and
-# optionally additional + 4 bytes for timestamp when not using
-# BT_ISO_TIMESTAMP_NONE in bt_iso_chan_send(), otherwise Host tries to fragment
-# ISO data.
-# When Host is fixed, CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE can inherit the
-# CONFIG_BT_ISO_TX_MTU value.
+# Support the highest SDU size required by any BAP LC3 presets (155) + 8 bytes of HCI ISO Data
+# packet overhead (the Packet_Sequence_Number, ISO_SDU_Length, Packet_Status_Flag fields; and
+# the optional Time_Stamp field, if supplied)
 CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=12
diff --git a/samples/bluetooth/iso_broadcast/sample.yaml b/samples/bluetooth/iso_broadcast/sample.yaml
@@ -17,8 +17,8 @@ tests:
       - qemu_cortex_m3
       - qemu_x86
       - nrf52_bsim
-      - nrf52dk/nrf52832
+      - nrf52833dk/nrf52833
     integration_platforms:
-      - nrf52dk/nrf52832
+      - nrf52833dk/nrf52833
     extra_args: OVERLAY_CONFIG=overlay-bt_ll_sw_split.conf
     tags: bluetooth
diff --git a/samples/bluetooth/public_broadcast_source/overlay-bt_ll_sw_split.conf b/samples/bluetooth/public_broadcast_source/overlay-bt_ll_sw_split.conf
@@ -14,11 +14,7 @@ CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX=155
 CONFIG_BT_CTLR_ADV_ISO_STREAM_MAX=2
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 
-# FIXME: Host needs CONFIG_BT_ISO_TX_MTU + 4 bytes for sequence number, and  optionally
-# additional + 4 bytes for timestamp when not using BT_ISO_TIMESTAMP_NONE in bt_iso_chan_send(),
-# otherwise Host tries to fragment ISO data.
-# When Host is fixed, CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE can inherit the
-# CONFIG_BT_ISO_TX_MTU value.
-#
-# Supports the highest SDU size required by any BAP LC3 presets (155)
+# Support the highest SDU size required by any BAP LC3 presets (155) + 8 bytes of HCI ISO Data
+# packet overhead (the Packet_Sequence_Number, ISO_SDU_Length, Packet_Status_Flag fields; and
+# the optional Time_Stamp field, if supplied)
 CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=163
diff --git a/samples/bluetooth/tmap_bmr/boards/nrf52840dk_nrf52840.conf b/samples/bluetooth/tmap_bmr/boards/nrf52840dk_nrf52840.conf
diff --git a/samples/bluetooth/tmap_bms/boards/nrf52840dk_nrf52840.conf b/samples/bluetooth/tmap_bms/boards/nrf52840dk_nrf52840.conf
diff --git a/samples/bluetooth/tmap_central/boards/nrf52840dk_nrf52840.conf b/samples/bluetooth/tmap_central/boards/nrf52840dk_nrf52840.conf
diff --git a/samples/bluetooth/tmap_peripheral/boards/nrf52840dk_nrf52840.conf b/samples/bluetooth/tmap_peripheral/boards/nrf52840dk_nrf52840.conf
diff --git a/samples/bluetooth/unicast_audio_client/boards/nrf52840dk_nrf52840.conf b/samples/bluetooth/unicast_audio_client/boards/nrf52840dk_nrf52840.conf
diff --git a/samples/bluetooth/unicast_audio_client/overlay-bt_ll_sw_split.conf b/samples/bluetooth/unicast_audio_client/overlay-bt_ll_sw_split.conf
@@ -1,9 +1,14 @@
 CONFIG_BT_LL_SW_SPLIT=y
 CONFIG_BT_CTLR_SCAN_DATA_LEN_MAX=1650
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=4
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=155
 CONFIG_BT_CTLR_ISOAL_SOURCES=2
 CONFIG_BT_CTLR_ISOAL_SINKS=1
+
+# Support the highest SDU size required by any BAP LC3 presets (155) + 8 bytes of HCI ISO Data
+# packet overhead (the Packet_Sequence_Number, ISO_SDU_Length, Packet_Status_Flag fields; and
+# the optional Time_Stamp field, if supplied)
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=163
+
 CONFIG_BT_CTLR_ADVANCED_FEATURES=y
 CONFIG_BT_CTLR_CONN_ISO_LOW_LATENCY_POLICY=y
 

diff --git a/samples/bluetooth/unicast_audio_server/boards/nrf52840dk_nrf52840.conf b/samples/bluetooth/unicast_audio_server/boards/nrf52840dk_nrf52840.conf
diff --git a/samples/bluetooth/unicast_audio_server/overlay-bt_ll_sw_split.conf b/samples/bluetooth/unicast_audio_server/overlay-bt_ll_sw_split.conf
@@ -1,10 +1,14 @@
 CONFIG_BT_LL_SW_SPLIT=y
 CONFIG_BT_CTLR_ADV_DATA_LEN_MAX=191
 CONFIG_BT_CTLR_ISO_TX_BUFFERS=2
-CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=155
 CONFIG_BT_CTLR_ISOAL_SOURCES=1
 CONFIG_BT_CTLR_ISOAL_SINKS=2
 
+# Support the highest SDU size required by any BAP LC3 presets (155) + 8 bytes of HCI ISO Data
+# packet overhead (the Packet_Sequence_Number, ISO_SDU_Length, Packet_Status_Flag fields; and
+# the optional Time_Stamp field, if supplied)
+CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE=163
+
 # Use the below if the sample is sending stale packet sequence number
 # CONFIG_BT_CTLR_ADVANCED_FEATURES=y
 # CONFIG_BT_CTLR_ISOAL_SN_STRICT=n
diff --git a/subsys/bluetooth/Kconfig.iso b/subsys/bluetooth/Kconfig.iso
@@ -105,14 +105,15 @@ config BT_ISO_TX_FRAG_COUNT
 
 config BT_ISO_TX_MTU
 	int "Maximum supported MTU for Isochronous TX buffers"
-	default 251
 	range 1 4095
+	default 247
 	help
 	  Maximum MTU for Isochronous channels TX buffers.
 	  This is the actual data payload. It doesn't include the optional
 	  HCI ISO Data packet fields (e.g. `struct bt_hci_iso_sdu_ts_hdr`).
 	  Set this value to 247 to fit 247 bytes of data within a single
-	  HCI ISO Data packet with a size of 255, without utilizing timestamps.
+	  HCI ISO Data packet with Data_Total_Length of 255, utilizing
+	  timestamps.
 
 config BT_ISO_RX_BUF_COUNT
 	int "Number of Isochronous RX buffers"

diff --git a/subsys/bluetooth/controller/Kconfig b/subsys/bluetooth/controller/Kconfig
@@ -202,12 +202,19 @@ config BT_CTLR_ISO_TX_BUFFERS
 config BT_CTLR_ISO_TX_BUFFER_SIZE
 	int "Isochronous Tx buffer size"
 	depends on BT_CTLR_ADV_ISO || BT_CTLR_CONN_ISO
-	range 1 4095
-	default BT_ISO_TX_MTU if BT_ISO
+	range 9 4103 if BT_LL_SW_SPLIT
+	range 1 65535
+	default 9 if BT_LL_SW_SPLIT
 	default 1
 	help
 	  Size of the Isochronous Tx buffers and the value returned in HCI LE
-	  Read Buffer Size V2 command response.
+	  Read Buffer Size V2 command response. This is the data portion of the
+	  HCI ISO Data packet, corresponding to the Data_Total_Length field.
+
+	  Currently the maximum SDU length is 4095 bytes, hence add HCI ISO
+	  Data packet overhead (the Packet_Sequence_Number, ISO_SDU_Length,
+	  Packet_Status_Flag fields; and the optional Time_Stamp field, if
+	  supplied) of 8 bytes.
 
 config BT_CTLR_ISOAL_SOURCES
 	int "Number of Isochronous Adaptation Layer sources"
@@ -929,7 +936,7 @@ config BT_CTLR_CONN_ISO_PDU_LEN_MAX
 config BT_CTLR_CONN_ISO_SDU_LEN_MAX
 	int "Maximum Connected Isochronous Channel SDU Length"
 	depends on BT_CTLR_CONN_ISO
-	range BT_CTLR_CONN_ISO_PDU_LEN_MAX 4095
+	range 1 4095
 	default 251
 	help
 	  Maximum Connected Isochronous Channel SDU Length.

diff --git a/subsys/bluetooth/controller/hci/hci.c b/subsys/bluetooth/controller/hci/hci.c
@@ -1398,7 +1398,7 @@ static void le_read_buffer_size_v2(struct net_buf *buf, struct net_buf **evt)
 
 	rp->acl_max_len = sys_cpu_to_le16(LL_LENGTH_OCTETS_TX_MAX);
 	rp->acl_max_num = CONFIG_BT_BUF_ACL_TX_COUNT;
-	rp->iso_max_len = sys_cpu_to_le16(CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE);
+	rp->iso_max_len = sys_cpu_to_le16(BT_CTLR_ISO_TX_BUFFER_SIZE);
 	rp->iso_max_num = CONFIG_BT_CTLR_ISO_TX_BUFFERS;
 }
 #endif /* CONFIG_BT_CTLR_ADV_ISO || CONFIG_BT_CTLR_CONN_ISO */

diff --git a/subsys/bluetooth/controller/include/ll_feat.h b/subsys/bluetooth/controller/include/ll_feat.h
@@ -189,10 +189,23 @@
 #define LL_FEAT_BIT_CIS_PERIPHERAL 0
 #endif /* !CONFIG_BT_CTLR_PERIPHERAL_ISO */
 
+#if defined(CONFIG_BT_CTLR_ADV_ISO) || defined(CONFIG_BT_CTLR_CONN_ISO)
+#if defined(CONFIG_BT_ISO_TX_MTU)
+#define BT_CTLR_ISO_TX_BUFFER_SIZE MIN((CONFIG_BT_ISO_TX_MTU + \
+					BT_HCI_ISO_SDU_TS_HDR_SIZE), \
+				       MAX(CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE, \
+					   (BT_HCI_ISO_SDU_TS_HDR_SIZE + 1U)))
+#else
+#define BT_CTLR_ISO_TX_BUFFER_SIZE MAX(CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE, \
+				       (BT_HCI_ISO_SDU_TS_HDR_SIZE + 1U))
+#endif /* CONFIG_BT_ISO_TX_MTU */
+#endif /* CONFIG_BT_CTLR_ADV_ISO || CONFIG_BT_CTLR_CONN_ISO */
+
 #if defined(CONFIG_BT_CTLR_CENTRAL_ISO) || \
 	defined(CONFIG_BT_CTLR_PERIPHERAL_ISO)
 #define LL_CIS_OCTETS_TX_MAX MIN(CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX, \
-				 CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE)
+				 (BT_CTLR_ISO_TX_BUFFER_SIZE - \
+				  BT_HCI_ISO_SDU_TS_HDR_SIZE))
 #define LL_CIS_OCTETS_RX_MAX CONFIG_BT_CTLR_CONN_ISO_PDU_LEN_MAX
 #else /* !CONFIG_BT_CTLR_CENTRAL_ISO && !CONFIG_BT_CTLR_PERIPHERAL_ISO */
 #define LL_CIS_OCTETS_TX_MAX 0
@@ -202,7 +215,8 @@
 #if defined(CONFIG_BT_CTLR_ADV_ISO)
 #define LL_FEAT_BIT_ISO_BROADCASTER BIT64(BT_LE_FEAT_BIT_ISO_BROADCASTER)
 #define LL_BIS_OCTETS_TX_MAX MIN(CONFIG_BT_CTLR_ADV_ISO_PDU_LEN_MAX, \
-				 CONFIG_BT_CTLR_ISO_TX_BUFFER_SIZE)
+				 (BT_CTLR_ISO_TX_BUFFER_SIZE - \
+				  BT_HCI_ISO_SDU_TS_HDR_SIZE))
 #else /* !CONFIG_BT_CTLR_ADV_ISO */
 #define LL_FEAT_BIT_ISO_BROADCASTER 0
 #define LL_BIS_OCTETS_TX_MAX 0