konfig.nrf: Bluetooth Add SOC dependent BT_TX_PROCESSOR_STACK_SIZE

Values were derived from Thread Analyzer results.
Applying SoC-specific defaults here to avoid touching upstream Zephyr
files.
Applications can still override via prj.conf.

BT_TX_PROCESSOR_STACK_SIZE config was disabled for the
samples/applications that don't have enough RAM to support it.

Signed-off-by: Kyra Lengfeld <[email protected]>

Author: KyraLengfeld

Kconfig.nrf

@@ -121,6 +121,24 @@ config NRF_SECURITY_ENABLER
 	imply MBEDTLS_ENABLE_HEAP if BT_HOST_CRYPTO_PRNG || BT_ECC || BT_GATT_CACHING || BT_CRYPTO
 	depends on !SOC_NRF5340_CPUNET
 
+# Bluetooth TX processor thread stack Thread Analyzer measurements
+# Apply SoC-specific defaults here to avoid touching upstream Zephyr files.
+# Applications can still override via prj.conf.
+configdefault BT_TX_PROCESSOR_STACK_SIZE
+	# nRF52 variants
+	default 768 if SOC_NRF52840
+	default 696 if SOC_NRF52832
+	default 969 if SOC_NRF52833
+	# nRF53 (application core)
+	default 688 if SOC_NRF5340_CPUAPP
+	# nRF54H20 (application core)
+	default 624 if SOC_NRF54H20_CPUAPP
+	# nRF54L15 (application core)
+	default 856 if SOC_NRF54L15_CPUAPP
+	# nRF54L V10A / LM20A (currently application core EngA variants are used)
+	default 856 if SOC_NRF54LV10A_ENGA_CPUAPP
+	default 856 if SOC_NRF54LM20A_ENGA_CPUAPP
+
 if SOC_SERIES_BSIM_NRFXX && ENTROPY_GENERATOR
 config MBEDTLS_HEAP_SIZE
 	int

applications/nrf_desktop/Kconfig

@@ -13,6 +13,23 @@ rsource "src/hw_interface/Kconfig"
 rsource "src/modules/Kconfig"
 rsource "src/util/Kconfig"
 rsource "Kconfig.defaults"
+
+# RAM reduction control: allow app to disable hidden Bluetooth TX processor thread.
+# Use an app-level switch that can be set per board in prj.conf.
+
+config DESKTOP_DISABLE_BT_TX_PROCESSOR_THREAD
+	bool "Disable BT TX processor thread to reduce RAM"
+	help
+	  Enable this to force the Bluetooth host hidden symbol BT_TX_PROCESSOR_THREAD off.
+	  Use on very constrained RAM boards (e.g. nrf52833dk/nrf52820, nrf52820dongle/nrf52820).
+
+if DESKTOP_DISABLE_BT_TX_PROCESSOR_THREAD
+
+config BT_TX_PROCESSOR_THREAD
+	bool
+	def_bool n
+
+endif
 endmenu
 
 menu "Zephyr Kernel"

applications/nrf_desktop/configuration/nrf52820dongle_nrf52820/prj.conf

@@ -85,6 +85,9 @@ CONFIG_BT_CTLR_DATA_LENGTH_MAX=35
 
 CONFIG_ENTROPY_CC3XX=n
 
+# Reduce RAM usage on this constrained board
+CONFIG_DESKTOP_DISABLE_BT_TX_PROCESSOR_THREAD=y
+
 ################################################################################
 
 CONFIG_ASSERT=y

applications/nrf_desktop/configuration/nrf52833dk_nrf52820/prj.conf

@@ -86,6 +86,9 @@ CONFIG_BT_CTLR_DATA_LENGTH_MAX=35
 
 CONFIG_ENTROPY_CC3XX=n
 
+# There is not enough RAM to support using this extra thread
+CONFIG_DESKTOP_DISABLE_BT_TX_PROCESSOR_THREAD=y
+
 ################################################################################
 
 CONFIG_ASSERT=y

applications/nrf_desktop/configuration/nrf52833dongle_nrf52833/prj.conf

@@ -80,6 +80,8 @@ CONFIG_BT_BUF_ACL_TX_SIZE=35
 CONFIG_BT_CTLR_DATA_LENGTH_MAX=35
 CONFIG_BT_CTLR_SDC_MAX_CONN_EVENT_LEN_DEFAULT=3000
 
+# There is not enough RAM to support using this extra thread
+
 ################################################################################
 
 CONFIG_ASSERT=y

samples/bluetooth/direction_finding_central/Kconfig

@@ -0,0 +1,15 @@
+# Override Bluetooth host defaults for this sample to reduce RAM usage.
+# We cannot modify Zephyr, so we adjust the default of the existing symbol here.
+# BT_TX_PROCESSOR_THREAD is a hidden (no prompt) symbol that defaults to 'y' on non-nRF51.
+# Provide a sample-level switch so boards can enable the reduction via their .conf.
+
+config DF_CENTRAL_DISABLE_BT_TX_THREAD
+	bool "Disable BT TX processor thread for DF central"
+
+if DF_CENTRAL_DISABLE_BT_TX_THREAD
+
+config BT_TX_PROCESSOR_THREAD
+	bool
+	def_bool n
+
+endif

samples/bluetooth/direction_finding_central/boards/nrf52833dk_nrf52820.conf

@@ -15,3 +15,8 @@ CONFIG_BT_CTLR_DF_CONN_CTE_REQ=y
 # Ensure that there are enough control procedure contexts to queue and execute all procedures
 CONFIG_BT_CTLR_LLCP_LOCAL_PROC_CTX_BUF_NUM=6
 CONFIG_BT_CTLR_ADVANCED_FEATURES=y
+
+# There is not enough RAM to support using this extra thread.
+# Do not set hidden Kconfig symbols in .conf files.
+# This is handled by the sample's Kconfig override via a sample-level switch.
+CONFIG_DF_CENTRAL_DISABLE_BT_TX_THREAD=y

samples/bluetooth/direction_finding_peripheral/Kconfig

@@ -0,0 +1,13 @@
+# Override Bluetooth host defaults for this sample to reduce RAM usage.
+# Provide a sample-level switch so boards can enable the reduction via their .conf.
+
+config DF_PERIPHERAL_DISABLE_BT_TX_THREAD
+	bool "Disable BT TX processor thread for DF peripheral"
+
+if DF_PERIPHERAL_DISABLE_BT_TX_THREAD
+
+config BT_TX_PROCESSOR_THREAD
+	bool
+	def_bool n
+
+endif

samples/bluetooth/direction_finding_peripheral/boards/nrf52833dk_nrf52820.conf

@@ -13,3 +13,6 @@ CONFIG_BT_CTLR_DF_CONN_CTE_RSP=y
 
 # Disable AoD Feature (antenna switching) in Tx mode in Controller
 CONFIG_BT_CTLR_DF_ANT_SWITCH_TX=n
+
+# Reduce RAM usage on this constrained board
+CONFIG_DF_PERIPHERAL_DISABLE_BT_TX_THREAD=y