linux-kernel - Re: [PATCH RFC 04/10] base: power: Add generic OF-based power domain look-up

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Date:	Mon, 20 Jan 2014 17:24:17 +0100
From:	Tomasz Figa <t.figa@...sung.com>
To:	Kevin Hilman <khilman@...aro.org>,
	Tomasz Figa <tomasz.figa@...il.com>
Cc:	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-samsung-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
	Russell King <linux@....linux.org.uk>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Kumar Gala <galak@...eaurora.org>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Mark Rutland <mark.rutland@....com>,
	Pawel Moll <pawel.moll@....com>,
	Rob Herring <robh+dt@...nel.org>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Stephen Warren <swarren@...dotorg.org>
Subject: Re: [PATCH RFC 04/10] base: power: Add generic OF-based power domain
 look-up

Hi Kevin,

On 14.01.2014 16:42, Kevin Hilman wrote:
> Tomasz Figa <tomasz.figa@...il.com> writes:
>
>> This patch introduces generic code to perform power domain look-up using
>> device tree and automatically bind devices to their power domains.
>> Generic device tree binding is introduced to specify power domains of
>> devices in their device tree nodes.
>>
>> Backwards compatibility with legacy Samsung-specific power domain
>> bindings is provided, but for now the new code is not compiled when
>> CONFIG_ARCH_EXYNOS is selected to avoid collision with legacy code. This
>> will change as soon as Exynos power domain code gets converted to use
>> the generic framework in further patch.
>>
>> Signed-off-by: Tomasz Figa <tomasz.figa@...il.com>
>
> I haven't read through this in detail yet, but wanted to make sure that
> the DT representation can handle nested power domains.  At least
> SH-mobile has a hierarchy of power domains and the genpd code can handle
> that, so wanted to make sure that the DT representation can handle it as
> well.

The representation of power domains themselves as implied by this patch 
is fully platform-specific. The only generic part is the 
#power-domain-cells property, which defines the number of cells needed 
to identify the power domain of given provider. You are free to have any 
platform-specific properties (or even generic ones, added on top of this 
patch) to let you specify the hierarchy in DT.

Best regards,
Tomasz
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