Android 9 Bluetooth Tethering Will disconnect.

[peterchao]

We have implemented bluetooth in Android tablet.
We were able to support bluetooth tethering to share wifi connection.
A PC connecte to tablet by bluetooth,
and can access tablet's wifi interenet by bluetooth tethering.

A few minutes, PC's bluetooth connection will disconnect,
then PC can not access internet by bluetooth tethering.

The BT module on our tablet is Marvell SD8997 WIFI/BT combo ,
and android 9 on i.MX8m.
The Bluetooth profile is tethering, and wifi connect to internet.

Could you help to check the reason of Bluetooth tethering disconnect?

Below is android log.

===========================================================

04-09 13:28:16.603 23262 23300 I bt_btm_sec: btm_sec_disconnected clearing pending flag handle:1 reason:8
04-09 13:28:16.603 23262 23284 I bt_btif_pan: bta_pan_callback_transfer: event = BTA_PAN_CLOSE_EVT handle 1
04-09 13:28:16.628 3176 3197 I EthernetTracker: interfaceLinkStateChanged, iface: bt-pan, up: false
04-09 13:28:16.636 3002 3035 I Netd : Destroyed 1 sockets on fe80::224e:f6ff:fe9e:a00e in 0.6 ms
04-09 13:28:16.638 3002 3035 D NetlinkEvent: Unknown ifindex 18 in RTM_DELADDR
04-09 13:28:16.638 3002 3035 I Netd : Destroyed 1 sockets on 192.168.44.1 in 0.7 ms
04-09 13:28:16.639 3029 3143 E display : threadLoop invalid uevent remove@/devices/virtual/net/bt-pan/queues/rx-0
04-09 13:28:16.640 3029 3143 E display : threadLoop invalid uevent remove@/devices/virtual/net/bt-pan/queues/tx-0
04-09 13:28:16.640 3029 3143 E display : threadLoop invalid uevent remove@/devices/virtual/net/bt-pan
04-09 13:28:16.641 3176 3334 D EthernetNetworkFactory: updateCapabilityFilter: []
04-09 13:28:16.647 3029 3143 E display : threadLoop invalid uevent change@/devices/virtual/xt_idletimer/timers
04-09 13:28:16.652 3002 3045 D TetherController: Sending update msg to dnsmasq [update_ifaces|bt-pan]
04-09 13:28:16.653 3002 3044 D TetherController: untetherInterface(bt-pan)
04-09 13:28:16.653 12346 12346 E dnsmasq : interface given in set_interfaces: 'bt-pan' has no ifindex; ignoring
04-09 13:28:16.654 12346 12346 I dnsmasq : Closing listener [fe80::224e:f6ff:fe9e:a00e%18]:53
04-09 13:28:16.654 12346 12346 I dnsmasq : Closing listener [192.168.44.1]:53
04-09 13:28:16.656 3002 3044 D CommandListener: Setting iface cfg
04-09 13:28:16.658 3176 3198 E Tethering: [bt-pan] ERROR Failed to clear IPv4 address on interface bt-pan: java.lang.IllegalStateException: command '427 interface setcfg bt-pan 0.0.0.0 0' failed with '400 427 Failed to clear address (No such device)'
04-09 13:28:16.661 3176 3176 W TelecomManager: Telecom Service not found.
04-09 13:28:16.663 3002 3044 D TetherController: Stopping tethering services
04-09 13:28:16.665 12346 12346 I dnsmasq : exiting on receipt of SIGTERM
04-09 13:28:16.666 3002 3044 D TetherController: Tethering services stopped
04-09 13:28:16.667 23262 23284 D BluetoothPanServiceJni: connection_state_callback(L82): state:2, local_role:1, remote_role:2
04-09 13:28:16.667 3002 3044 D TetherController: Setting IP forward enable = 0
04-09 13:28:16.667 23262 23284 I btif_av : btif_av_acl_disconnected: Peer 7c:d3:0a:41:a4:eb : ACL Disconnected
04-09 13:28:16.667 23262 23262 D PanService: handlePanDeviceStateChange preState: 2 state: 0
04-09 13:28:16.667 23262 23300 I btif_av : BtifAvPeer *BtifAvSource::FindOrCreatePeer(const RawAddress &, tBTA_AV_HNDL): Create peer: peer_address=7c:d3:0a:41:a4:eb bta_handle=0x41 peer_id=0
04-09 13:28:16.667 23262 23262 I PanService: remote(PANU) is disconnected, Remaining connected PANU devices: 0
04-09 13:28:16.667 23262 23262 I PanService: configureBtIface: bt-pan enable: false
04-09 13:28:16.667 23262 23300 W bt_btif : btif_av_get_peer_sep: No active peer found
04-09 13:28:16.667 23262 23300 I bt_btif_a2dp: btif_a2dp_on_idle: ## ON A2DP IDLE ## peer_sep = 1
04-09 13:28:16.667 23262 23300 W bt_btif : btif_av_get_peer_sep: No active peer found
04-09 13:28:16.667 23262 23300 I bt_btif_a2dp_source: btif_a2dp_source_on_idle: state=STATE_OFF
04-09 13:28:16.667 23262 23300 W bt_btif : btif_av_get_peer_sep: No active peer found
04-09 13:28:16.667 23262 23300 I bt_btif_a2dp: btif_a2dp_on_idle: ## ON A2DP IDLE ## peer_sep = 1
04-09 13:28:16.667 23262 23300 W bt_btif : btif_av_get_peer_sep: No active peer found
04-09 13:28:16.667 23262 23300 I bt_btif_a2dp_source: btif_a2dp_source_on_idle: state=STATE_OFF
04-09 13:28:16.667 23262 23300 I btif_av : DeleteIdlePeers: Deleting idle peer: 7c:d3:0a:41:a4:eb bta_handle=0x41
04-09 13:28:16.668 3176 3313 D ConnectivityService: releasing NetworkRequest [ REQUEST id=70, [ Capabilities: INTERNET&NOT_RESTRICTED&TRUSTED&NOT_VPN Unwanted: ] ] (release request)
04-09 13:28:16.672 23262 23262 D PanService: Pan Device state : device: 7C:D3:0A:41:A4:EB State:2->0
04-09 13:28:16.673 23262 23262 D BluetoothMapService: onReceive
04-09 13:28:16.673 23262 23262 D BluetoothMapService: onReceive: android.bluetooth.device.action.ACL_DISCONNECTED
04-09 13:28:16.674 3520 3520 D CachedBluetoothDevice: onProfileStateChanged: profile PAN, device=7C:D3:0A:41:A4:EB, newProfileState 0
04-09 13:28:16.675 23262 23262 D AdapterProperties: PROFILE_CONNECTION_STATE_CHANGE: profile=5, device=7C:D3:0A:41:A4:EB, 2 -> 0
04-09 13:28:16.676 23262 23262 W AdapterProperties: PROFILE_CONNECTION_STATE_CHANGE: unexpected transition for profile=5, device=7C:D3:0A:41:A4:EB, 2 -> 0
04-09 13:28:16.676 3381 3535 D CachedBluetoothDevice: onProfileStateChanged: profile PAN, device=7C:D3:0A:41:A4:EB, newProfileState 0
04-09 13:28:16.676 23262 23262 D AdapterProperties: ADAPTER_CONNECTION_STATE_CHANGE: 7C:D3:0A:41:A4:EB: 2 -> 0
04-09 13:28:16.676 23262 23262 W AdapterProperties: ADAPTER_CONNECTION_STATE_CHANGE: unexpected transition for profile=5, device=7C:D3:0A:41:A4:EB, 2 -> 0
04-09 13:28:16.678 23196 23196 I wpa_supplicant: the mrvl nl80211 driver cmd is BTCOEXSCAN-STOP
04-09 13:28:16.678 23196 23196 I wpa_supplicant: the nl80211 driver cmd len is 15
04-09 13:28:16.678 23196 23196 I wpa_supplicant: Use private command =====
04-09 13:28:25.084 3029 3143 E display : threadLoop invalid uevent change@/devices/platform/30a40000.i2c/i2c-2/2-006a/power_supply/battery
04-09 13:28:35.324 3029 3143 E display : threadLoop invalid uevent change@/devices/platform/30a40000.i2c/i2c-2/2-006a/power_supply/battery
04-09 13:28:42.980 3029 3143 E display : threadLoop invalid uevent change@/devices/virtual/xt_idletimer/timers
04-09 13:28:45.564 3029 3143 E display : threadLoop invalid uevent change@/devices/platform/30a40000.i2c/i2c-2/2-006a/power_supply/battery
04-09 13:28:55.804 3029 3143 I chatty : uid=1000(system) HWC-UEvent-Thre identical 1 line
04-09 13:29:06.044 3029 3143 E display : threadLoop invalid uevent change@/devices/platform/30a40000.i2c/i2c-2/2-006a/power_supply/battery
04-09 13:29:07.184 3029 3143 E display : threadLoop invalid uevent change@/devices/virtual/xt_idletimer/timers

Best Regards, 

Peter