Hello there,

I am working on an embedded system to support USB Bluetooth dongles.
* Soc: Altera Cyclone V SoC FPGA
* Linux: Ångström distribution with kernel version is 4.17 and 4.19
* USB Bluetooth dongle: Broadcom chip, connected as USB1.1

I have a problem of that an USB Bluetooth dongle seems to stop 
responding to host's HCI commands suddenly.
These are example error messages I got when it stops response.
[  145.046503] Bluetooth: hci0: command 0x1002 tx timeout
[  147.086503] Bluetooth: hci0: command 0x0c52 tx timeout
[  149.121499] Bluetooth: hci0: command 0x0c45 tx timeout
[  151.166503] Bluetooth: hci0: command 0x0c58 tx timeout

I do not find out what is the trigger of this problem.
Sometimes the dongle is working (used as a Bluetooth PAN server) 
initially but suddenly gives the timeout error then stop responding.
Sometimes the error happens just immediately after I insert the dongle.
There does not seem to be specific HCI commands to cause the error. The 
command in the error messages varies.

The attached dmesg log (dmesg_log.txt) and USB packet dump 
(USB_Dump.pcapng can be opened by Wireshark) have been taken while the 
system cold boot, inserting the dongle and the error happens.

In frame no. 161 of the packet dump, the host sent HCI command 0x1002 
(Read Local Supported Commands).
Then the USB dongle tried to respond to that from frame no. 163 but it 
did not sent all fragment packets. It seems to stop response in the middle.
Finally, "[  145.046503] Bluetooth: hci0: command 0x1002 tx timeout" 
happened (Please refer dmesg_log.txt attached).

As for frame no. 165, the host sent 0x0c52 (Write Extended Inquiry 
Response) but there was no response to it then "[  147.086503] 
Bluetooth: hci0: command 0x0c52 tx timeout" happened.


I disabled the following kernel options related to power management but 
the error still happening.
* CPU Frequency scaling
* CPU idle PM support
* Suspend to RAM and standby
* Hibernation (aka 'suspend to disk')
* Device power management core functionality
* Advanced Power Management Emulation

I also disabled kernel options under "Bluetooth subsystem support" (so 
only "Bluetooth subsystem support" is enabled) but still it is happening.

I tried to reduce some USB kernel options and enabled just only the 
following stuff but it did not make any difference.
* Support for Host-side USB
* USB announce new devices
* DesignWare USB2 DRD Core Support

The dongle is detected in hardware level even when this problem is 
happening as I can see it on "hciconfig".


It would be great if you would give me your thoughts.

Thank you in advance,

Mori