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

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Message-ID: <PAXPR04MB91851302EAB989EC8261AEFD89E0A@PAXPR04MB9185.eurprd04.prod.outlook.com>
Date:   Mon, 28 Aug 2023 19:23:46 +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: [EXT] 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 2:12 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...
> >>
> >
> > When you talk about the chip, can you please be more specific?
> 
> What to say more? The device node you quoted above is the regulator. You
> brought specific example and now claim this is not a regulator, but just GPIO.
> Please fix your DTS.
> 

The fixed-regulator is a virtual regulator driver that uses the GPIO pin. You claimed this 
as a hardware chip.

The regulator-pd driver also uses the same GPIO pin. You now claimed this as a software layer.

What's your standard?

Thanks,
Shenwei

> >
> > Regarding the dts node, how about the example in the fixed-regulator.yaml
> under the bindings directory.
> 
> That's an example, how is it related to anything?
> 
> >
> >     reg_1v8: regulator-1v8 {
> >       compatible = "regulator-fixed";
> >       regulator-name = "1v8";
> >       regulator-min-microvolt = <1800000>;
> >       regulator-max-microvolt = <1800000>;
> >       gpio = <&gpio1 16 0>;
> >       startup-delay-us = <70000>;
> >       enable-active-high;
> >       regulator-boot-on;
> >       gpio-open-drain;
> >       vin-supply = <&parent_reg>;
> >     };
> >
> > If you take a look at the fixed regulator driver (fixed.c), I don't
> > think you'll find anything related to a hardware component (chip) other than
> the GPIO Pin.
> 
> That's a driver. How is it related to this discussion? Bindings are not about
> drivers.
> 
> 
> Best regards,
> Krzysztof