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

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Message-ID: <2bde5922-6519-4b6d-9edf-94fd0e7dbc9d@oss.qualcomm.com>
Date: Wed, 12 Nov 2025 10:49:03 +0100
From: Konrad Dybcio <konrad.dybcio@....qualcomm.com>
To: Wei Deng <wei.deng@....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

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?

Konrad