Created attachment 289213 [details]
>>My tablet uses AP6255 wifi/bluetooth module with BCM43455 chip.
>>The bluetooth controller worked well except bluetooth headset play sound
>>glitch.It's not configuration problem in bluez or pulseaudio.
>>Some log in dmesg indicated that baud rate was not correctly configured.
>>>Bluetooth: BCM: failed to write clock (-56)
>>>Bluetooth: Failed to set baudrate.
>Steps to Reproduce:
>>1. Power on bluetooth headset.
>>2. If it was not automatically connect, connect to headset by bluetoothctl.
>>3. play sound.
>>I suspect the baud rate was too low to transmit audio.
>>It seems the chip can't support write clock HCI command. Then bluetooth
>>driver used default 115200 baud rate.
>>I tried to force configure 4Mbps baud rate to my chip after write clock
>>failed, but reset it failed. Then I hardcode baud rate to 3Mbps, it solved
>>the glitch problem.
>>And I found the commit that introduced the 4Mbsp to ACPI device:
>>It seems not all ACPI discovered devices can support write clock.
>>So maybe the driver should fallback baud rate to 3Mbps if write clock failed.
Smiles ^__________^ zech