linux-kernel - Re: [PATCH 2/7] dt-bindings: PM / OPP: add clocks per OPP node support

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Message-ID: <20170831173920.4emtr5vkgvjcx6ac@rob-hp-laptop>
Date:   Thu, 31 Aug 2017 12:39:20 -0500
From:   Rob Herring <robh@...nel.org>
To:     Dong Aisheng <aisheng.dong@....com>
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, sboyd@...eaurora.org,
        vireshk@...nel.org, nm@...com, rjw@...ysocki.net,
        shawnguo@...nel.org, Anson.Huang@....com, ping.bai@....com,
        Frank Rowand <frowand.list@...il.com>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH 2/7] dt-bindings: PM / OPP: add clocks per OPP node
 support

On Thu, Aug 24, 2017 at 12:10:05AM +0800, Dong Aisheng wrote:
> It's used for platforms where different OPPs may use different clocks.
> With this extended binding, user could specify the correct clock for each
> OPP node.
> 
> Cc: Viresh Kumar <vireshk@...nel.org>
> Cc: Nishanth Menon <nm@...com>
> Cc: Stephen Boyd <sboyd@...eaurora.org>
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: Frank Rowand <frowand.list@...il.com>
> Cc: devicetree@...r.kernel.org
> Signed-off-by: Dong Aisheng <aisheng.dong@....com>
> ---
>  Documentation/devicetree/bindings/opp/opp.txt | 52 +++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
> index e36d261..40a4340 100644
> --- a/Documentation/devicetree/bindings/opp/opp.txt
> +++ b/Documentation/devicetree/bindings/opp/opp.txt
> @@ -152,6 +152,11 @@ Optional properties:
>    hierarchy can be contained in multiple 32 bit values. i.e. <X Y Z1 Z2> in the
>    above example, Z1 & Z2 refer to the version hierarchy Z.
>  
> +- clocks: Clock phandle and specifier used for this opp.
> +
> +- clock-names: clock names for this opp. The valid clock names are platform
> +	       specific.

You don't need -names if there's only 1 clock. But then how long until 
we have a list of any random clocks some how associated with an OPP.

I think this should really be solved within the clock framework. What 
you really need is "set my parent clock to the source that can provide X 
Hz". Could the assigned-clocks property work here (in the OPP nodes 
rather than the cpu nodes)?

> +
>  - status: Marks the node enabled/disabled.
>  
>  Example 1: Single cluster Dual-core ARM cortex A9, switch DVFS states together.
> @@ -528,3 +533,50 @@ Example 6: opp-microvolt-<name>, opp-microamp-<name>:
>  		};
>  	};
>  };
> +
> +Example 7: Single core ARM cortex A7, switch separate clocks for each OPP:

Can't you add this to an existing example? We don't need to enumerate 
every possible option.

Rob