Bluetooth: Controller: Assertion in lll.c when using hci_uart sample for mcumgr to perform DFU

[cvinayak]

Describe the bug

mcumgr[33668]: < ACL Data TX: Handle 0 flags 0x01 dlen 16                                                                                                                               #399648 [hci1] 35513.296191
      ATT: Write Command (0x52) len 497
        Handle: 0x000e Type: Vendor specific (da2e7828-fbce-4e01-ae9e-261174997c48)
          Data[239]: 020001e700012d01a364646174615901ce616365206b6579206d6f64652e0a536f6d65207465726d696e616c7320617265206e6f742073656e64696e672073657061726174652065736361706520636f646520666f72206261636b737061636520616e642064656c65746520627574746f6e2e205468697320636f6d6d616e6420666f72636573207368656c6c20746f20696e746572707265742064656c657465206b6579206173206261636b73706163652e00636f6c6f72730000546f67676c6520636f6c6f7265642073796e7461782e00007674313030000000546f67676c6520767431303020636f6d6d616e
> HCI Event: Number of Completed Packets (0x13) plen 5                                                                                                                                  #399649 [hci1] 35513.298228
        Num handles: 1
        Handle: 0 Address: F4:81:FA:23:32:D0 (Static)
        Count: 2
        #399639: len 27 (43 Kb/s)
        Latency: 5 msec (2-20 msec ~4 msec)
        #399641: len 27 (43 Kb/s)
        Latency: 5 msec (2-20 msec ~5 msec)
mcumgr[33668]: < ACL Data TX: Handle 0 flags 0x00 dlen 27                                                                                                                               #399650 [hci1] 35513.298557
mcumgr[33668]: < ACL Data TX: Handle 0 flags 0x01 dlen 27                                                                                                                               #399651 [hci1] 35513.298575
> HCI Event: Number of Completed Packets (0x13) plen 5                                                                                                                                  #399652 [hci1] 35513.298691
        Num handles: 1
        Handle: 0 Address: F4:81:FA:23:32:D0 (Static)
        Count: 1
        #399643: len 27 (108 Kb/s)
        Latency: 2 msec (2-20 msec ~4 msec)
mcumgr[33668]: < ACL Data TX: Handle 0 flags 0x01 dlen 27                                                                                                                               #399653 [hci1] 35513.298910
> HCI Event: Number of Completed Packets (0x13) plen 5                                                                                                                                  #399654 [hci1] 35513.301236
        Num handles: 1
        Handle: 0 Address: F4:81:FA:23:32:D0 (Static)
        Count: 2
        #399644: len 27 (43 Kb/s)
        Latency: 5 msec (2-20 msec ~4 msec)
        #399646: len 27 (43 Kb/s)
        Latency: 5 msec (2-20 msec ~4 msec)
mcumgr[33668]: < ACL Data TX: Handle 0 flags 0x01 dlen 27                                                                                                                               #399655 [hci1] 35513.301558
mcumgr[33668]: < ACL Data TX: Handle 0 flags 0x01 dlen 27                                                                                                                               #399656 [hci1] 35513.301576
> HCI Event: Vendor (0xff) plen 11                                                                                                                                                      #399657 [hci1] 35513.389374
        aa 6c 6c 6c 2e 63 00 7c 03 00 00                 .lll.c.|...     

Regression

• This is a regression.

Steps to reproduce

# Build and flash uart_hci onto nRF52840-DK
west build -p auto -d build_uart_hci/ --board nrf52840dk/nrf52840 samples/bluetooth/hci_uart
west flash -d build_uart_hci

# Build device firmware A
west build -p auto -d build_A --board nrf54l15dk/nrf54l15/cpuapp samples/subsys/mgmt/mcumgr/smp_svr/ -DCONFIG_DEBUG=y -DCONFIG_MCUMGR_TRANSPORT_BT_PERM_RW=y -DCONFIG_BT_DEVICE_NAME=\"firmwareA\" -DEXTRA_CONF_FILE="overlay-bt.conf" --sysbuild
# Build and flash device firmware B onto nRF54l15-DK
west build -p auto -d build_B --board nrf54l15dk/nrf54l15/cpuapp samples/subsys/mgmt/mcumgr/smp_svr/ -DCONFIG_DEBUG=y -DCONFIG_MCUMGR_TRANSPORT_BT_PERM_RW=y -DCONFIG_BT_DEVICE_NAME=\"firmwareB\" -DEXTRA_CONF_FILE="overlay-bt.conf" --sysbuild
west flash -d build_B

# Attach HCI
sudo btattach -S 1000000 -B /dev/ttyACM1 &
# Start FOTA to firmware A
sudo mcumgr --conntype ble --hci 1 --timeout 60 --connstring peer_name=\"firmwareA\" image upload build_A/smp_svr/zephyr/zephyr.signed.bin
# Start FOTA to firmware B
sudo mcumgr --conntype ble --hci 1 --timeout 60 --connstring peer_name=\"firmwareB\" image upload build_B/smp_svr/zephyr/zephyr.signed.bin

Relevant log output

Impact

Annoyance – Minor irritation; no significant impact on usability or functionality.

Environment

• Commit SHA: 4852719

Additional Context

No response