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

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Date:   Mon, 28 Aug 2023 18:39:41 +0000
From:   Shenwei Wang <shenwei.wang@....com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        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



> -----Original Message-----
> From: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> Sent: Monday, August 28, 2023 12:11 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
> On 28/08/2023 16:04, Shenwei Wang wrote:
> 
> >>> 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. 
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.

Thanks,
Shenwei

> > Similarly, "regulator-pd" provides a software abstraction layer for
> > virtual PD devices built on top of existing regulator drivers.
> 
> This is not related to regulator-fixed at all.
> 
> > When looking at the conceptual purpose, regulator-fixed and
> > regulator-pd are comparable in that they both offer software abstraction
> layers for virtual devices."
> 
> No. regulator-fixed is a real device. Yours is not.
> 
> 
> Best regards,
> Krzysztof