linux-kernel - Re: [PATCH v4 1/4] dt-bindings/opp: Update documentation for opp-shared

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Message-ID: <bfb6a380-645e-d721-4610-be73ab4f2dcd@arm.com>
Date:   Tue, 8 Dec 2020 07:15:30 +0000
From:   Nicola Mazzucato <nicola.mazzucato@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-pm@...r.kernel.org, devicetree@...r.kernel.org,
        sudeep.holla@....com, rjw@...ysocki.net, vireshk@...nel.org,
        robh+dt@...nel.org, sboyd@...nel.org, nm@...com,
        daniel.lezcano@...aro.org, morten.rasmussen@....com,
        chris.redpath@....com
Subject: Re: [PATCH v4 1/4] dt-bindings/opp: Update documentation for
 opp-shared

Hi Viresh,

thanks for your comments. I will update subject and content as you suggested.

Regards,
Nicola

On 12/8/20 4:29 AM, Viresh Kumar wrote:
> Subject should rather be:
> 
> dt-bindings: opp: Allow empty OPP tables
> 
> On 02-12-20, 17:23, Nicola Mazzucato wrote:
>> Currently the optional property opp-shared is used within an opp table
>> to tell that a set of devices share their clock/voltage lines (and the
>> opp points).
>> It is therefore possible to use an empty opp table to convey only that
>> information, useful in situations where the opp points are provided via
>> other means (hardware. firmware, etc).
>>
>> Update the documentation to remark this additional case and provide an
>> example.
>>
>> Signed-off-by: Nicola Mazzucato <nicola.mazzucato@....com>
>> ---
>>  Documentation/devicetree/bindings/opp/opp.txt | 53 +++++++++++++++++++
>>  1 file changed, 53 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
>> index 9847dfeeffcb..a5f1f993eab9 100644
>> --- a/Documentation/devicetree/bindings/opp/opp.txt
>> +++ b/Documentation/devicetree/bindings/opp/opp.txt
>> @@ -72,6 +72,9 @@ Optional properties:
>>    switch their DVFS state together, i.e. they share clock/voltage/current lines.
>>    Missing property means devices have independent clock/voltage/current lines,
>>    but they share OPP tables.
>> +  This optional property can be used without any OPP nodes when its only purpose
>> +  is to describe a dependency of clock/voltage/current lines among a set of
>> +  devices.
> 
> And instead of this, we should rather update "OPP nodes:" section like
> this:
> 
> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
> index 9847dfeeffcb..28077ce3a845 100644
> --- a/Documentation/devicetree/bindings/opp/opp.txt
> +++ b/Documentation/devicetree/bindings/opp/opp.txt
> @@ -63,11 +63,13 @@ This describes the OPPs belonging to a device. This node can have following
>  - compatible: Allow OPPs to express their compatibility. It should be:
>    "operating-points-v2".
>  
> +Optional properties:
>  - OPP nodes: One or more OPP nodes describing voltage-current-frequency
>    combinations. Their name isn't significant but their phandle can be used to
> -  reference an OPP.
> +  reference an OPP. These are mandatory except for the case where the OPP table
> +  is present only to indicate dependency between devices using the opp-shared
> +  property.
>  
> -Optional properties:
>  - opp-shared: Indicates that device nodes using this OPP Table Node's phandle
>    switch their DVFS state together, i.e. they share clock/voltage/current lines.
>    Missing property means devices have independent clock/voltage/current lines,
>