linux-kernel - Re: [RFC PATCH v2 3/4] powerpc: refactor of_get_cpu_node to support other architectures

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Date:	Mon, 19 Aug 2013 08:02:52 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Mark Rutland <mark.rutland@....com>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Jonas Bonn <jonas@...thpole.se>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Michal Simek <monstr@...str.eu>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@....com>,
	Tomasz Figa <tomasz.figa@...il.com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [RFC PATCH v2 3/4] powerpc: refactor of_get_cpu_node to support
 other architectures

On 08/19/2013 05:19 AM, Mark Rutland wrote:
> On Sat, Aug 17, 2013 at 11:09:36PM +0100, Benjamin Herrenschmidt wrote:
>> On Sat, 2013-08-17 at 12:50 +0200, Tomasz Figa wrote:
>>> I wonder how would this handle uniprocessor ARM (pre-v7) cores, for
>>> which 
>>> the updated bindings[1] define #address-cells = <0> and so no reg 
>>> property.
>>>
>>> [1] - http://thread.gmane.org/gmane.linux.ports.arm.kernel/260795
>>
>> Why did you do that in the binding ? That sounds like looking to create
>> problems ... 
>>
>> Traditionally, UP setups just used "0" as the "reg" property on other
>> architectures, why do differently ?
> 
> The decision was taken because we defined our reg property to refer to
> the MPIDR register's Aff{2,1,0} bitfields, and on UP cores before v7
> there's no MPIDR register at all. Given there can only be a single CPU
> in that case, describing a register that wasn't present didn't seem
> necessary or helpful.

What exactly reg represents is up to the binding definition, but it
still should be present IMO. I don't see any issue with it being
different for pre-v7.

Rob

> 
> Thanks,
> Mark.
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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