linux-kernel - Re: [PATCH v2 3/3] dt-bindings: mfd: stpmic1: add fsl,pmic-poweroff property

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Date:   Tue, 23 May 2023 18:29:15 +0100
From:   Conor Dooley <conor@...nel.org>
To:     Sean Nyekjær <sean@...nix.com>
Cc:     robh+dt@...nel.org, Lee Jones <lee@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        pascal Paillet <p.paillet@...s.st.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/3] dt-bindings: mfd: stpmic1: add fsl,pmic-poweroff
 property

On Tue, May 23, 2023 at 11:55:50AM +0200, Sean Nyekjær wrote:
> > On 16 May 2023, at 20.06, Conor Dooley <conor@...nel.org> wrote:
> > On Tue, May 16, 2023 at 03:22:24PM +0200, Sean Nyekjaer wrote:
> >> Document the new optional "fsl,pmic-poweroff" property.
> >> 
> >> Signed-off-by: Sean Nyekjaer <sean@...nix.com>
> >> ---
> >> Documentation/devicetree/bindings/mfd/st,stpmic1.yaml | 8 ++++++++
> >> 1 file changed, 8 insertions(+)
> >> 
> >> diff --git a/Documentation/devicetree/bindings/mfd/st,stpmic1.yaml b/Documentation/devicetree/bindings/mfd/st,stpmic1.yaml
> >> index 9573e4af949e..5183a7c660d2 100644
> >> --- a/Documentation/devicetree/bindings/mfd/st,stpmic1.yaml
> >> +++ b/Documentation/devicetree/bindings/mfd/st,stpmic1.yaml
> >> @@ -26,6 +26,14 @@ properties:
> >> 
> >>   interrupt-controller: true
> >> 
> >> +  st,pmic-poweroff:
> >> +    $ref: /schemas/types.yaml#/definitions/flag
> >> +    description: |
> >> +      if present, configure the PMIC to shutdown all power rails when
> >> +      power off sequence have finished.
> >> +      Use this option if the SoC should be powered off by external power management
> >> +      IC (PMIC).
> > 
> > Just reading this description, this is sounding quite like a "software
> > behaviour" type of property, which are not permitted, rather than
> > describing some element of the hardware. Clearly you are trying to solve
> > an actual problem though, so try re-phrasing the description (and
> > property name) to focus on what exact hardware configuration it is that
> > you are trying to special-case.
> > Krzysztof suggested that the samsung,s2mps11-acokb-ground property in
> > samsung,s2mps11.yaml is addressing a similar problem, so that could be
> > good to look at.
> 
> Better wording?
>       Indicates that the power management IC (PMIC) is used to power off the board.
>       So as the last step in the power off sequence set the SWOFF bit in the
>       main control register (MAIN_CR) register, to shutdown all power rails.

The description for the property that Krzysztof mentioned is
  samsung,s2mps11-acokb-ground:
    description: |
      Indicates that ACOKB pin of S2MPS11 PMIC is connected to the ground so
      the PMIC must manually set PWRHOLD bit in CTRL1 register to turn off the
      power. Usually the ACOKB is pulled up to VBATT so when PWRHOLD pin goes
      low, the rising ACOKB will trigger power off.

In other words, I am asking what (abnormal?) scenario there is that means
you need the property, rather than what setting the property does.
Or am I totally off, and this is the only way this PMIC works?

Cheers,
Conor.

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