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: <5DA89267.30806@linaro.org>
Date:   Thu, 17 Oct 2019 12:10:15 -0400
From:   Thara Gopinath <thara.gopinath@...aro.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     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 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>;
                                };
				
> 
> From Linux point of view, it means you can use dev_pm_domain_attach()
> to hook up the corresponding device with the PM domain.

Yes. Only the thermal framework does not populate cdev->dev->of_node.
But it should be a trivial thing to fix it. Also if I end up creating a
separate device, it should not matter.
> 
> Using "power-domain-names" is just to allow to specify a name rather
> than an index, which makes sense if there is more than one index.
> Perhaps you can state that the "power-domain-names" should be there
> anyway, to be a little bit future proof if ever multiple index
> (multiple PM domains).
> 
> Kind regards
> Uffe
> 


-- 
Warm Regards
Thara