linux-kernel - Re: [PATCH 1/2] dt-bindings: power: Add regulator-pd yaml file

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Message-ID: <f3e89479-14ab-d1d0-ad87-6f457f313c39@linaro.org>
Date:   Mon, 28 Aug 2023 20:52:30 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Shenwei Wang <shenwei.wang@....com>,
        Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        "imx@...ts.linux.dev" <imx@...ts.linux.dev>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH 1/2] dt-bindings: power: Add regulator-pd yaml file

On 28/08/2023 20:50, Shenwei Wang wrote:
> 
> 
>> -----Original Message-----
>> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
>> Sent: Monday, August 28, 2023 1:42 PM
>> To: Shenwei Wang <shenwei.wang@....com>; Ulf Hansson
>> <ulf.hansson@...aro.org>
>> Cc: Rob Herring <robh+dt@...nel.org>; Krzysztof Kozlowski
>> <krzysztof.kozlowski+dt@...aro.org>; Conor Dooley <conor+dt@...nel.org>;
>> Liam Girdwood <lgirdwood@...il.com>; Mark Brown <broonie@...nel.org>;
>> imx@...ts.linux.dev; devicetree@...r.kernel.org; linux-kernel@...r.kernel.org;
>> dl-linux-imx <linux-imx@....com>
>> Subject: [EXT] Re: [PATCH 1/2] dt-bindings: power: Add regulator-pd yaml file
>>>>>>> Are you suggesting to move the regulator-pd to the imx directory
>>>>>>> and add a company prefix to the compatible string?
>>>>>>
>>>>>> There is no such part of iMX processor as such
>>>>>> regulator-power-domain, so I don't recommend that approach. DTS
>>>>>> nodes represent hardware, not your SW layers.
>>>>>>
>>>>>
>>>>> That's not always the case, as we do sometimes need a virtual device.
>>>>> As an example, the "regulator-fixed" acts as a software abstraction
>>>>> layer to create virtual regulator devices by interfacing with the
>>>>> underlying
>>>> GPIO drivers.
>>>>
>>>> Not true. This is a real regulator device. Real hardware on the board.
>>>> You can even see and touch it.
>>>>
>>>
>>> The physical hardware component is the GPIO pin, which is what you can only
>> touch.
>>
>> No. The regulator is the chip.
>>
> 
> In the definition of dts node below, where is the chip? The real hardware is just a GPIO Pin.
>     reg1: regulator-1 {
>     	compatible = "regulator-fixed";
>     	regulator-name = "REG1";
>     	regulator-min-microvolt = <3000000>;
>     	regulator-max-microvolt = <3000000>;
>     	gpio = <&lsio_gpio4 19 GPIO_ACTIVE_HIGH>;
>     	enable-active-high;
>     };

There is a chip. This is the chip. If you have there only GPIO pin, then
your DTS is just wrong. Drop it. If you learn from wrong DTS, then sure,
power-domain-regulator seems like great idea...

> 
>>> The regulator functions virtually through software layer above of the
>>> GPIO driver. While we may call it a "regulator" or whatever else, this
>>> cannot obscure the fact that the underlying hardware is just a GPIO pin being
>> used in a specialized way.
>>
>> The regulator is some tiny little box, you can touch and called
>> ti,tps51632 or similar.
>>
> 
> We are talking about the specific "regulator-fixed" driver, why did you bring up "ti,tps51632" here?

Just an example. Can be TPS123098.

Best regards,
Krzysztof