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

[Shuai Zhang]

Hi Konrad

Thanks for your review.

On 3/13/2026 8:34 PM, Konrad Dybcio wrote:
> 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?

Yes, this is an M.2 slot that can accommodate different types of cards.
Additionally, the maintainer proposed option [1], which should be able 
to resolve my issue.

I am currently evaluating it.

[1]https://lore.kernel.org/r/20260224-pci-m2-e-v5-9-dd9b9501d33c@xxxxxxxxxxxxxxxx

> Konrad


Thanks,
Shuai