Bug 207843 - Some ACPI discovered BRCM HCI UART chip write clock failed.
Summary: Some ACPI discovered BRCM HCI UART chip write clock failed.
Status: NEW
Alias: None
Product: Drivers
Classification: Unclassified
Component: Bluetooth (show other bugs)
Hardware: All Linux
: P1 low
Assignee: linux-bluetooth@vger.kernel.org
Depends on:
Reported: 2020-05-22 02:56 UTC by zechfox
Modified: 2020-05-22 02:56 UTC (History)
0 users

See Also:
Kernel Version: 5.6.13
Tree: Mainline
Regression: No

dmesg output (62.98 KB, text/plain)
2020-05-22 02:56 UTC, zechfox

Description zechfox 2020-05-22 02:56:53 UTC
Created attachment 289213 [details]
dmesg output

>>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.
>Actual Results:
>>sound glitches.
>Expect Results:
>>sound well.
>Additional Information: 
>>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

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