linux-kernel - Re: [PATCH v10 2/6] dt-bindings: opp: v2-qcom-level: Document CPR3 open/closed loop volt adjustment

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Message-ID: <1274e18b-e35e-7997-68ea-22aa11592720@collabora.com>
Date:   Mon, 20 Feb 2023 12:27:18 +0100
From:   AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh@...nel.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        Niklas Cassel <nks@...wful.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Robert Marko <robimarko@...il.com>,
        linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-pm@...r.kernel.org
Subject: Re: [PATCH v10 2/6] dt-bindings: opp: v2-qcom-level: Document CPR3
 open/closed loop volt adjustment

Il 18/02/23 01:26, Konrad Dybcio ha scritto:
> 
> 
> On 18.02.2023 00:13, Rob Herring wrote:
>> On Fri, Feb 17, 2023 at 12:08:25PM +0100, Konrad Dybcio wrote:
>>> CPR3 and newer can be fed per-OPP voltage adjustment values for both
>>> open- and closed-loop paths to make better decisions about settling
>>> on the final voltage offset target. Document these properties.
>>>
>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@...aro.org>
>>> ---
>>>   .../devicetree/bindings/opp/opp-v2-qcom-level.yaml         | 14 ++++++++++++++
>>>   1 file changed, 14 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/opp/opp-v2-qcom-level.yaml b/Documentation/devicetree/bindings/opp/opp-v2-qcom-level.yaml
>>> index a30ef93213c0..93cc88434dfe 100644
>>> --- a/Documentation/devicetree/bindings/opp/opp-v2-qcom-level.yaml
>>> +++ b/Documentation/devicetree/bindings/opp/opp-v2-qcom-level.yaml
>>> @@ -34,6 +34,20 @@ patternProperties:
>>>           minItems: 1
>>>           maxItems: 2
>>>   
>>> +      qcom,opp-cloop-vadj:
>>> +        description: |
>>> +          A value representing the closed-loop voltage adjustment value
>>
>> A value?
>>
>>> +          associated with this OPP node.
>>> +        $ref: /schemas/types.yaml#/definitions/int32-array
>>> +        maxItems: 2
>>
>> Or 2 values?
> Right, this description doesn't make any sense if you're just
> looking at the documentation without looking at the driver..
> 
> Generally, each CPR3 instance can have multiple "threads"
> (each one of which regulates voltage for some on-SoC IP or
> part of it). The nth entry in the qcom,opp-[co]loop-vadj
> array corresponds to a voltage offset for the nth thread.
> 
> If the nth entry in the array is missing, the driver assumes
> the arr[0] one is "global" to this CPR3 instance at this OPP
> level and applies it to all threads. ...and looking at it
> again, this is sorta just bad design, especially if you
> take into account that there's no known user of CPR3 that
> employs more than 2 threads.
> 
> I'll remove that from the driver and make the description clearer.
> 

description:
   Represents the closed-loop voltage adjustment associated with
   this OPP node.

P.S.: Drop '|' here and on oloop!

This binding is intended to support either single or multiple CPR threads;
the driver's behavior is unimportant as bindings describe the hardware,
not the driver.

Regards,
Angelo

> 
> Also, only noticed now.. "qcom,sdm630-cprh" was not documented,
> so that's to be fixed for the next submission as well!
> 
> 
> Konrad
>>
>>> +
>>> +      qcom,opp-oloop-vadj:
>>> +        description: |
>>> +          A value representing the open-loop voltage adjustment value
>>> +          associated with this OPP node.
>>> +        $ref: /schemas/types.yaml#/definitions/int32-array
>>> +        maxItems: 2
>>> +
>>>       required:
>>>         - opp-level
>>>         - qcom,opp-fuse-level
>>>
>>> -- 
>>> 2.39.1
>>>