linux-kernel - Re: [PATCH] ARM: dts: msm8974: Move arch-timer out of soc node

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Message-ID: <53273566.20208@codeaurora.org>
Date:	Mon, 17 Mar 2014 13:48:22 -0400
From:	Christopher Covington <cov@...eaurora.org>
To:	Kumar Gala <galak@...eaurora.org>
CC:	Stephen Boyd <sboyd@...eaurora.org>,
	David Brown <davidb@...eaurora.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] ARM: dts: msm8974: Move arch-timer out of soc node

Hi Kumar,

On 03/17/2014 01:33 PM, Kumar Gala wrote:
> 
> On Mar 17, 2014, at 12:31 PM, Christopher Covington <cov@...eaurora.org> wrote:
> 
>> Hi Stephen,
>>
>> On 03/11/2014 05:24 PM, Stephen Boyd wrote:
>>> The architected timer is not a register addressable piece of
>>> hardware. Instead it's accessed through cp15 accessors. Move it
>>> to the root of the devicetree to reflect this.
>>
>> I find this confusing, perhaps due to overloading of the word "register".
>> Aren't CP15's a class of coprocessor _registers_? Could it perhaps be clearer
>> to talk about memory-mapped versus CP15-mapped timers?
>>
>> Is "soc" documented somewhere or is it just a name for a container? Assuming
>> the latter, it's not obvious to me why being a child of a system on chip node
>> would imply having memory mapped registers.
> 
> “soc” is a container, since its compatible = "simple-bus”, this implies
> memory mapped register access for nodes inside of it.

That makes sense. Thanks for explaining it.

Christopher

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