linux-kernel - Re: [PATCH v3 4/4] arm64: dts: qcom: Add base HAMOA-IOT-EVK board

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Message-ID: <c0b804e3-16ee-4e81-9aa8-4b6051b5af03@quicinc.com>
Date: Tue, 29 Jul 2025 17:39:02 +0800
From: Yingying Tang <quic_yintang@...cinc.com>
To: Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Yijie Yang
	<yijie.yang@....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>, Shuai Zhang <shuaz@....qualcomm.com>,
        <quic_miaoqing@...cinc.com>, <quic_zhichen@...cinc.com>
Subject: Re: [PATCH v3 4/4] arm64: dts: qcom: Add base HAMOA-IOT-EVK board



On 7/29/2025 4:37 PM, Konrad Dybcio wrote:
> On 7/29/25 7:51 AM, Yijie Yang wrote:
>>
>>
>> On 2025-07-29 09:32, Yijie Yang wrote:
>>> The HAMOA-IOT-EVK is an evaluation platform for IoT products, composed of
>>> the Hamoa IoT SoM and a carrier board. Together, they form a complete
>>> embedded system capable of booting to UART.
>>>
>>> This change enables and overlays the following peripherals on the carrier
>>> board:
>>> - UART
>>> - On-board regulators
>>> - USB Type-C mux
>>> - Pinctrl
>>> - Embedded USB (EUSB) repeaters
>>> - NVMe
>>> - pmic-glink
>>> - USB DisplayPorts
>>>
>>> Written with contributions from Shuai Zhang (added Bluetooth) and Yongxing
>>> Mou (added USB DisplayPorts).
>>>
>>> Signed-off-by: Yijie Yang <yijie.yang@....qualcomm.com>
>>> ---
> 
> [...]>> +    vreg_wcn_3p3: regulator-wcn-3p3 {
>>> +        compatible = "regulator-fixed";
>>> +
>>> +        regulator-name = "VREG_WCN_3P3";
>>> +        regulator-min-microvolt = <3300000>;
>>> +        regulator-max-microvolt = <3300000>;
>>> +
>>> +        gpio = <&tlmm 214 GPIO_ACTIVE_HIGH>;
>>> +        enable-active-high;
>>> +
>>> +        pinctrl-0 = <&wcn_sw_en>;
>>> +        pinctrl-names = "default";
>>> +
>>> +        regulator-boot-on;
>>
>> It should be set to 'regulator-always-on'.
> 
> Are you sure? Turning off Wi-Fi sounds like a valid usecase..

Hi Konard, It is m.2 interface on Hamoa. The PCIe power of m.2 should be always on.

Even on QCOM's B2B interface, we are unable to dynamically control the power of PCIe devices on upstream kernel.
The PCIe specification does not support dynamic power control between the PCIe device and the RC.
PCIe power should be always on here.
> 
> Konrad