Re: [PATCH v1] arm64: dts: qcom: hamoa-iot-evk: support Bluetooth over both USB and UART

[Konrad Dybcio]

On 3/13/26 7:37 AM, Shuai Zhang wrote:
> Hi Konrad
> 
> On 3/11/2026 9:07 PM, Konrad Dybcio wrote:
>> On 3/11/26 10:09 AM, Shuai Zhang wrote:
>>> When Bluetooth supports both USB and UART, the BT UART driver is
>>> always loaded, while USB is hot-pluggable. As a result, when Bluetooth
>>> is used over USB, the UART driver still be probed and drive BT_EN low,
>>> which causes the Bluetooth device on USB to be disconnected.
>> Is bluetooth connected over UART *and* USB simultaneously?
> BT uses either UART or USB, never both at the same time.
> 
> On platforms supporting both, the UART driver is always probed, while USB is hot‑pluggable.
> 
> As a result, when BT runs over USB, the UART driver still probes and pulls BT_EN low,
> 
> unintentionally powering off the USB BT device.

Please describe in more detail how that difference can appear in practice.

Is there an M.2 slot, into which different kinds of cards (i.e. ones with
BT-over-USB vs BT-over-UART) may be plugged in?

Konrad