linux-kernel - Re: [PATCH 2/2] dt-bindings: mfd: cros-ec: add properties for thermal cooling cells

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Message-ID: <Z0Pl3muZx716QSed@google.com>
Date: Mon, 25 Nov 2024 10:50:06 +0800
From: "Sung-Chi, Li" <lschyi@...omium.org>
To: Krzysztof Kozlowski <krzk@...nel.org>
Cc: Benson Leung <bleung@...omium.org>, Guenter Roeck <groeck@...omium.org>,
	Sebastian Reichel <sre@...nel.org>, Lee Jones <lee@...nel.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, chrome-platform@...ts.linux.dev,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	devicetree@...r.kernel.org
Subject: Re: [PATCH 2/2] dt-bindings: mfd: cros-ec: add properties for
 thermal cooling cells

On Fri, Nov 22, 2024 at 08:49:14AM +0100, Krzysztof Kozlowski wrote:
> On Fri, Nov 22, 2024 at 11:47:22AM +0800, Sung-Chi Li wrote:
> > The cros_ec supports limiting the input current to act as a passive
> > thermal cooling device. Add the property '#cooling-cells' bindings, such
> > that thermal framework can recognize cros_ec as a valid thermal cooling
> > device.
> > 
> > Signed-off-by: Sung-Chi Li <lschyi@...omium.org>
> > ---
> >  Documentation/devicetree/bindings/mfd/google,cros-ec.yaml | 3 +++
> >  1 file changed, 3 insertions(+)
> > 
> > diff --git a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> > index aac8819bd00b..2b6f098057af 100644
> > --- a/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> > +++ b/Documentation/devicetree/bindings/mfd/google,cros-ec.yaml
> > @@ -96,6 +96,9 @@ properties:
> >    '#gpio-cells':
> >      const: 2
> >  
> > +  '#cooling-cells':
> > +    const: 2
> 
> This is not a cooling device. BTW, your commit msg is somehow circular.
> "Add cooling to make it a cooling device because it will be then cooling
> device."
> 
> Power supply already provides necessary framework for managing charging
> current and temperatures. If this is to stay, you need to explain why
> this is suitable to be considered a thermal zone or system cooling
> device (not power supply or input power cooling).
> 
> Best regards,
> Krzysztof
> 

Thank you, I will rephrase the commit message. The reason to not to use the
managing charging current and temperatures in the power supply framework is
that:

- The EC may not have the thermal sensor value for the charger, and there is no
  protocol for getting the thermal sensor value for the charger (there is
  command for reading thermal sensor values, but there is no specification for
  what sensor index is for the charger, if the charger provides thermal value).
- The managing mechanism only take the charger thermal value into account, and
  I would like to control the current based on the thermal condition of the
  whole device.

I will include these explanation in the following changes.