linux-kernel - Re: [PATCH 2/2] arm64: dts: lx2160a: add device tree for lx2162aqds board

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Message-ID: <20200921130325.GA25428@dragon>
Date:   Mon, 21 Sep 2020 21:03:27 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Meenakshi Aggarwal <meenakshi.aggarwal@....com>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Varun Sethi <V.Sethi@....com>, Leo Li <leoyang.li@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Kuldeep Singh <kuldeep.singh@....com>
Subject: Re: [PATCH 2/2] arm64: dts: lx2160a: add device tree for lx2162aqds
 board

On Mon, Sep 21, 2020 at 06:00:53AM +0000, Meenakshi Aggarwal wrote:
> 
> 
> > -----Original Message-----
> > From: Shawn Guo <shawnguo@...nel.org>
> > Sent: Saturday, September 12, 2020 3:19 PM
> > To: Meenakshi Aggarwal <meenakshi.aggarwal@....com>
> > Cc: robh+dt@...nel.org; Varun Sethi <V.Sethi@....com>; Leo Li
> > <leoyang.li@....com>; linux-arm-kernel@...ts.infradead.org;
> > devicetree@...r.kernel.org; linux-kernel@...r.kernel.org; Ioana Ciornei
> > <ioana.ciornei@....com>; Kuldeep Singh <kuldeep.singh@....com>
> > Subject: Re: [PATCH 2/2] arm64: dts: lx2160a: add device tree for lx2162aqds
> > board
> > 
> > On Wed, Sep 09, 2020 at 07:10:12AM +0000, Meenakshi Aggarwal wrote:
> > > > > +	sb_3v3: regulator-sb3v3 {
> > > > > +		compatible = "regulator-fixed";
> > > > > +		regulator-name = "MC34717-3.3VSB";
> > > > > +		regulator-min-microvolt = <3300000>;
> > > > > +		regulator-max-microvolt = <3300000>;
> > > > > +		regulator-boot-on;
> > > > > +		regulator-always-on;
> > > >
> > > > I do not see any point to have regulator-boot-on or
> > > > regulator-always-on for a regulator that doesn't have on/off control.
> > > [Meenakshi Aggarwal] Properties are added to specify that platform
> > > firmware's out of reset configuration enabled the regulator and regulator
> > should never be disabled or change its operative status.
> > 
> > What I was wondering if how this regulator is enabled by firmware, by some
> > GPIO control?  In that case, 'gpio' property should be there to describe the GPIO
> > control.
> > 
> [Meenakshi Aggarwal] Its not controlled by GPIO. Its gets power on with board.
> > >
> > > Can you help in understanding why these optional properties cannot be
> > > used together
> > 
> > It's totally fine to use these properties together.  But if the regulator doesn't
> > have on/off control, neither of them makes sense.
> [Meenakshi Aggarwal] As per documentation, we should keep " regulator-always-on " as per description, we
> Can remove " regulator-boot-on" property from dts.
> 
> regulator-always-on:
>     description: boolean, regulator should never be disabled                                  

Again, the property is only meaningful for a regulator that can possibly
be disabled.

Shawn