linux-kernel - Re: [PATCH] arm64: dts: qcom: lemans-evk: Enable Bluetooth support

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Message-ID: <5a8d75a3-b20e-4de4-b15d-a56af503324d@oss.qualcomm.com>
Date: Thu, 13 Nov 2025 20:38:04 +0800
From: Wei Deng <wei.deng@....qualcomm.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        stable@...r.kernel.org, cheng.jiang@....qualcomm.com,
        quic_jiaymao@...cinc.com, quic_chezhou@...cinc.com,
        quic_shuaz@...cinc.com
Subject: Re: [PATCH] arm64: dts: qcom: lemans-evk: Enable Bluetooth support

Hi Konrad，
Thanks for your comments.

On 11/12/2025 5:49 PM, Konrad Dybcio wrote:
> On 11/11/25 1:24 PM, Wei Deng wrote:
>> Hi Konrad,
>>
>> Thanks for your comments.
>>
>> On 11/10/2025 7:49 PM, Konrad Dybcio wrote:
>>> On 11/10/25 6:57 AM, Wei Deng wrote:
>>>> There's a WCN6855 WiFi/Bluetooth module on an M.2 card. To make
>>>> Bluetooth work, we need to define the necessary device tree nodes,
>>>> including UART configuration and power supplies.
>>>>
>>>> Since there is no standard M.2 binding in the device tree at present,
>>>> the PMU is described using dedicated PMU nodes to represent the
>>>> internal regulators required by the module.
>>>>
>>>> The 3.3V supply for the module is assumed to come directly from the
>>>> main board supply, which is 12V. To model this in the device tree, we
>>>> add a fixed 12V regulator node as the DC-IN source and connect it to
>>>> the 3.3V regulator node.
>>>>
>>>> Signed-off-by: Wei Deng <wei.deng@....qualcomm.com>
>>>> ---
>>>
>>> [...]
>>>
>>>>  &apps_rsc {
>>>> @@ -627,6 +708,22 @@ &qupv3_id_2 {
>>>>  	status = "okay";
>>>>  };
>>>>  
>>>> +&qup_uart17_cts {
>>>> +	bias-disable;
>>>> +};
>>>> +
>>>> +&qup_uart17_rts {
>>>> +	bias-pull-down;
>>>> +};
>>>> +
>>>> +&qup_uart17_tx {
>>>> +	bias-pull-up;
>>>> +};
>>>> +
>>>> +&qup_uart17_rx {
>>>> +	bias-pull-down;
>>>> +};
>>>
>>> This is notably different than all other platforms' bluetooth pin
>>> settings - for example pulling down RX sounds odd, since UART signal
>>> is supposed to be high at idle
>>>
>>> see hamoa.dtsi : qup_uart14_default as an example
>>>
>>
>> I followed the qup_uart17 settings from lemans-ride-common.dtsi. Since these configurations are not required for Bluetooth functionality. I will remove this configuration in the next patch.
> 
> This feels like you're essentially saying you don't know/care why you
> did this before and don't know why you're changing it again. This
> doesn't give me a lot of confidence. Are you testing your changes on
> real hw, running an upstream kernel with some distro userland?
> 

We add qup_uart17 config followed the changes referenced in the below 
link and validated them on the hardware platform. Bluetooth functionality
works fine before and after the removal.
https://lore.kernel.org/all/20250509090443.4107378-1-quic_vdadhani@quicinc.com/

> Konrad

-- 
Best Regards,
Wei Deng