linux-kernel - Re: [PATCH v3 6/7] dt-bindings: soc: qcom: Extend RPMh power controller binding to describe thermal warming device

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Message-ID: <20191029013648.GB27045@bogus>
Date:   Mon, 28 Oct 2019 20:36:48 -0500
From:   Rob Herring <robh@...nel.org>
To:     Thara Gopinath <thara.gopinath@...aro.org>
Cc:     Ulf Hansson <ulf.hansson@...aro.org>,
        Eduardo Valentin <edubezval@...il.com>,
        Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>, amit.kucheria@...durent.com,
        Mark Rutland <mark.rutland@....com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 6/7] dt-bindings: soc: qcom: Extend RPMh power
 controller binding to describe thermal warming device

On Thu, Oct 17, 2019 at 12:10:15PM -0400, Thara Gopinath wrote:
> On 10/17/2019 11:43 AM, Ulf Hansson wrote:
> > On Thu, 17 Oct 2019 at 17:28, Thara Gopinath <thara.gopinath@...aro.org> wrote:
> >>
> >> Hello Ulf,
> >> Thanks for the review!
> >>
> >> On 10/17/2019 05:04 AM, Ulf Hansson wrote:
> >>> On Wed, 16 Oct 2019 at 21:37, Thara Gopinath <thara.gopinath@...aro.org> wrote:
> >>>>
> >>>> RPMh power controller hosts mx domain that can be used as thermal
> >>>> warming device. Add a sub-node to specify this.
> >>>>
> >>>> Signed-off-by: Thara Gopinath <thara.gopinath@...aro.org>
> >>>> ---
> >>>>  Documentation/devicetree/bindings/power/qcom,rpmpd.txt | 10 ++++++++++
> >>>>  1 file changed, 10 insertions(+)
> >>>>
> >>>> diff --git a/Documentation/devicetree/bindings/power/qcom,rpmpd.txt b/Documentation/devicetree/bindings/power/qcom,rpmpd.txt
> >>>> index eb35b22..fff695d 100644
> >>>> --- a/Documentation/devicetree/bindings/power/qcom,rpmpd.txt
> >>>> +++ b/Documentation/devicetree/bindings/power/qcom,rpmpd.txt
> >>>> @@ -18,6 +18,16 @@ Required Properties:
> >>>>  Refer to <dt-bindings/power/qcom-rpmpd.h> for the level values for
> >>>>  various OPPs for different platforms as well as Power domain indexes
> >>>>
> >>>> += SUBNODES
> >>>> +RPMh alsp hosts power domains that can behave as thermal warming device.
> >>>> +These are expressed as subnodes of the RPMh. The name of the node is used
> >>>> +to identify the power domain and must therefor be "mx".
> >>>> +
> >>>> +- #cooling-cells:
> >>>> +       Usage: optional
> >>>> +       Value type: <u32>
> >>>> +       Definition: must be 2
> >>>> +
> >>>
> >>> Just wanted to express a minor thought about this. In general we use
> >>> subnodes of PM domain providers to represent the topology of PM
> >>> domains (subdomains), this is something different, which I guess is
> >>> fine.
> >>>
> >>> I assume the #cooling-cells is here tells us this is not a PM domain
> >>> provider, but a "cooling device provider"?
> >> Yep.
> >>>
> >>> Also, I wonder if it would be fine to specify "power-domains" here,
> >>> rather than using "name" as I think that is kind of awkward!?
> >> Do you mean "power-domain-names" ? I am using this to match against the
> >> genpd names defined in the provider driver.
> > 
> > No. If you are using "power-domains" it means that you allow to
> > describe the specifier for the provider.
> Yep. But won't this look funny in DT ? The provider node will have a sub
> node with a power domain referencing to itself Like below: Is this ok ?
> 
> rpmhpd: power-controller {
>                                 compatible = "qcom,sdm845-rpmhpd";
>                                 #power-domain-cells = <1>;
> 
> 			...
> 			...
> 				mx_cdev: mx {
>                                         #cooling-cells = <2>;
>                                         power-domains = <&rpmhpd	SDM845_MX>;
>                                 };
> 				

The whole concept here seems all wrong to me. Isn't it what's in the 
power domain that's the cooling device. A CPU power domain is not a 
cooling device, the CPU is. Or we wouldn't make a clock a cooling 
device, but what the clock drives.

Rob