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

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Date:   Wed, 24 May 2023 10:16:13 +0200
From:   Sean Nyekjær <sean@...nix.com>
To:     Conor Dooley <conor@...nel.org>
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

Hi Conor,

> On 23 May 2023, at 19.29, Conor Dooley <conor@...nel.org> wrote:
> 
> 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?

Indicates that the power management IC (PMIC) turn-off condition is met
by setting the SWOFF bit in the main control register (MAIN_CR) register.
Turn-off condition can still be reached by the PONKEY input.

?

I must admit I’m somewhat lost here :)

/Sean