linux-kernel - Re: [PATCH 2/5] arm64: dts: qcom: qcm6490-fairphone-fp5: Add VTOF_LDO

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Message-Id: <DDDPKMMSAMJR.1JIQMK3W2Y40V@fairphone.com>
Date: Thu, 09 Oct 2025 12:10:33 +0200
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: "Konrad Dybcio" <konrad.dybcio@....qualcomm.com>, "Luca Weiss"
 <luca.weiss@...rphone.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>, "Marijn Suijten" <marijn.suijten@...ainline.org>
Cc: <~postmarketos/upstreaming@...ts.sr.ht>, <phone-devel@...r.kernel.org>,
 <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] arm64: dts: qcom: qcm6490-fairphone-fp5: Add
 VTOF_LDO_2P8 regulator

On Thu Oct 9, 2025 at 11:22 AM CEST, Konrad Dybcio wrote:
> On 10/9/25 11:16 AM, Luca Weiss wrote:
>> Hi Konrad,
>> 
>> On Wed Oct 1, 2025 at 10:30 AM CEST, Konrad Dybcio wrote:
>>> On 9/30/25 3:57 PM, Luca Weiss wrote:
>>>> Describe yet another regulator-fixed on this board, powering the ToF
>>>> sensor.
>>>>
>>>> Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
>>>> ---
>>>>  arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts | 13 +++++++++++++
>>>>  1 file changed, 13 insertions(+)
>>>>
>>>> diff --git a/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts b/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
>>>> index 36d5750584831d66b4c2faf6042e4cbb3274eca7..0a64e5721e092d1f3e4bb7329335704eee567761 100644
>>>> --- a/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
>>>> +++ b/arch/arm64/boot/dts/qcom/qcm6490-fairphone-fp5.dts
>>>> @@ -195,6 +195,19 @@ vreg_usb_redrive_1v8: regulator-usb-redrive-1v8 {
>>>>  		pinctrl-names = "default";
>>>>  	};
>>>>  
>>>> +	vreg_vtof_ldo_2p8: regulator-vtof-ldo-2p8 {
>>>> +		compatible = "regulator-fixed";
>>>> +		regulator-name = "VTOF_LDO_2P8";
>>>> +		regulator-min-microvolt = <2800000>;
>>>> +		regulator-max-microvolt = <2800000>;
>>>> +		regulator-enable-ramp-delay = <233>;
>>>> +
>>>> +		gpio = <&tlmm 141 GPIO_ACTIVE_HIGH>;
>>>
>>> You may want to define the pincfg/mux config for this gpio too
>> 
>> While I wouldn't say it's not good to have it, there's plenty of GPIOs
>> that have no pinctrl for it. Downstream doesn't set anything for gpio141
>> either.
>> 
>> I honestly wouldn't even know what the 'default' for a GPIO is in the
>> first place, or could I query the runtime state from the kernel? Is
>> /sys/kernel/debug/pinctrl/f100000.pinctrl/pinconf-groups trustworthy to
>> solidify this in the dts?
>
> I normally use /sys/kernel/debug/gpios

Oh, if that works at least the path is a bit more memorable. I needed to
check quite some files in this directory to find the correct one.

>
>> 
>> 141 (gpio141): input bias disabled, output drive strength (2 mA), output enabled, pin output (0 level)
>
> but this seems to be formatted very similarly if not identically
>
> Generally it reads out HW state, via (among other things)
> msm_config_group_get()

So, you recommend setting a pinctrl for every single GPIO that's
referenced in the dts? Shall I send a patch to add all the missing ones?

Regards
Luca

>
> Konrad