linux-kernel - Re: [PATCH/RFC 1/5] dt-bindings: mfd: bd9571mwv: Document rohm,ddr-backup-power

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Date:   Fri, 13 Oct 2017 11:00:16 +0100
From:   Lee Jones <lee.jones@...aro.org>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Marek Vasut <marek.vasut+renesas@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Simon Horman <horms@...ge.net.au>,
        Magnus Damm <magnus.damm@...il.com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux PM list <linux-pm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH/RFC 1/5] dt-bindings: mfd: bd9571mwv: Document
 rohm,ddr-backup-power

On Fri, 13 Oct 2017, Geert Uytterhoeven wrote:

> Hi Lee,
> 
> On Fri, Oct 13, 2017 at 10:55 AM, Lee Jones <lee.jones@...aro.org> wrote:
> > On Tue, 10 Oct 2017, Geert Uytterhoeven wrote:
> >> Document the new optional "rohm,ddr-backup-power" property.
> >>
> >> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> >> ---
> >>  Documentation/devicetree/bindings/mfd/bd9571mwv.txt | 7 +++++++
> >>  1 file changed, 7 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/mfd/bd9571mwv.txt b/Documentation/devicetree/bindings/mfd/bd9571mwv.txt
> >> index 9ab216a851d5619b..7ea3f2db41d4e501 100644
> >> --- a/Documentation/devicetree/bindings/mfd/bd9571mwv.txt
> >> +++ b/Documentation/devicetree/bindings/mfd/bd9571mwv.txt
> >> @@ -25,6 +25,12 @@ Required properties:
> >>                           Each child node is defined using the standard
> >>                           binding for regulators.
> >>
> >> +Optional properties:
> >> +  - rohm,ddr-backup-power : Value to use for DDR-Backup Power.  This controls
> >> +                         which DDR rails need to be kept powered when backup
> >> +                         mode is enabled, cfr. the KEEPON_DDR* bits in the
> >
> > Perhaps it's just me, but I'm confused by this line.
> >
> > Can you word it another way?
> 
> I'll ttry... Let me think a bit about it...

I think it's just the "cfr" which is throwing me.

> >> +                         documentation for the "BKUP Mode Cnt" register.
> >> +
> >>  Example:
> >>
> >>       pmic: pmic@30 {
> >> @@ -36,6 +42,7 @@ Example:
> >>               #interrupt-cells = <2>;
> >>               gpio-controller;
> >>               #gpio-cells = <2>;
> >> +             rohm,ddr-backup-power = <15>;
> >
> > Can you explain what this means?  Is it a mask, or does line 15 need
> > to be kept on?  What is the range?  Is 0 acceptable?  Clarification
> > required please.
> 
> It's a mask (OR of (in this case all four) needed KEEPON_DDR* bits).
> Unfortunately the datasheet is not publicly available.
> 
> 0 is acceptable, but as the property is optional, you better just leave it out.

Would you mind reflecting that in the doc please?

Maybe a few more examples will help?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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