linux-kernel - Re: [PATCH 1/2] PM / OPP: add support to specify phandle of another node for OPP

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Message-ID: <519110DF.9070403@arm.com>
Date:	Mon, 13 May 2013 17:12:15 +0100
From:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>
To:	Nishanth Menon <nm@...com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>
CC:	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Rob Landley <rob@...dley.net>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Shawn Guo <shawn.guo@...aro.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>
Subject: Re: [PATCH 1/2] PM / OPP: add support to specify phandle of another
 node for OPP

Hi device-tree folks,

On 01/05/13 15:41, Nishanth Menon wrote:
> On 12:11-20130501, Sudeep.KarkadaNagesha@....com wrote:
>> From: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
>>
>> If more than one similar devices share the same OPPs, currently we
>> need to replicate the OPP entries in all the nodes.
> Nice, thanks.
>>
>> Few drivers like cpufreq depend on physical cpu0 node to specify the
> cpufreq-cpu0?
>> OPPs and only that node is referred irrespective of the logical cpu
>> accessing it. Alternatively to support cpuhotplug path, few drivers
>> parse all the cpu nodes for OPPs. Instead we can specify the phandle
>> of the node with which the current node shares the operating points.
>>
>> This patch adds support to specify the phandle in the operating points
>> of any device node, where the node specified by the phandle holds the
>> actual OPPs.
>>
>> Signed-off-by: Sudeep KarkadaNagesha <sudeep.karkadanagesha@....com>
>> ---
>>  Documentation/devicetree/bindings/power/opp.txt |   41 +++++++++++++++++++++++
>>  drivers/base/power/opp.c                        |   30 ++++++++++++-----
>>  2 files changed, 63 insertions(+), 8 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/power/opp.txt b/Documentation/devicetree/bindings/power/opp.txt
>> index 74499e5..a659da4 100644
>> --- a/Documentation/devicetree/bindings/power/opp.txt
>> +++ b/Documentation/devicetree/bindings/power/opp.txt
>> @@ -23,3 +23,44 @@ cpu@0 {
>>              198000  850000
>>      >;
>>  };
>> +
> Definition of operating-points is now a little different in the
> original description - it still indicates tuple {freq,voltage}, where
> as, this patch allows phandle to a different device's operating-points
> to be used. - we might want to rephrase the description.
>
> btw, to device-tree folks, I am not sure if it is OK to have different formats
> for the same property like operating-points. At least I don't seem to
> quickly be able to find any precedence.
>
Any directions on this to proceed ? Is proposed option of phandle for
OPP acceptable ?

Regards,
Sudeep

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