linux-kernel - Re: [PATCH RFC v2 07/12] PM / Domains: export pm_genpd_lookup

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Date:	Fri, 28 Nov 2014 14:22:09 +0530
From:	amit daniel kachhap <amit.daniel@...sung.com>
To:	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
	Kukjin Kim <kgene.kim@...sung.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>,
	Pankaj Dubey <pankaj.dubey@...sung.com>,
	Kevin Hilman <khilman@...nel.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH RFC v2 07/12] PM / Domains: export pm_genpd_lookup_name

On Thu, Nov 27, 2014 at 7:50 PM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
> On 25 November 2014 at 09:48, amit daniel kachhap
> <amit.daniel@...sung.com> wrote:
>> On Tue, Nov 25, 2014 at 1:05 PM, Ulf Hansson <ulf.hansson@...aro.org> wrote:
>>> On 24 November 2014 at 14:04, Amit Daniel Kachhap
>>> <amit.daniel@...sung.com> wrote:
>>>> This API may be needed to set the power domain parent/child relationship
>>>> in the power domain platform driver. The parent relationship is
>>>> generally set after the child power domain is registered with the power
>>>> domain subsystem. In this case, pm_genpd_lookup_name API might be
>>>> useful.
>>>
>>> I think this is a step in the wrong direction. Instead we should be
>>> working on removing the "name" based APIs from genpd.
>>>
>>> The proper way should be to pass the PM domain as a parameter to the
>>> APIs instead.
>> Yes i understand but i had a special requirement for using this API
>> during pd probe.
>>  I cannot use hierarchy to represent parent/child pd nodes as it will
>> break the existing SoC's. In my case all the PD nodes are linear. The
>> parent/child relationship are established in the second pass after all
>> the PD entries are registered with the help of this API.
>> Although there a way that i can always keep parent PD's before the
>> child PD's in DT in linear order. Will check this approach.
>
> I had some thinking around this, could the below approach work?
>
> I just posted a patch[1] adding a new pm_genpd_lookup() API, which is
> using a "DT device node" to fetch the genpd. The idea is to use that
> API to get the genpd handle which is needed to configure a subdomain
> through pm_genpd_add_subdomain() API.
I looked at your patch. I seems fine. i will test them and post the
new version of my series.

Regards,
Amit D
>
> In principle you will have to walk through the DT a couple of times,
> initialize those domains (and subdomains) which either don't have a
> parent domain or which parent domain already has been initialized. I
> guess you need a somewhat clever loop to do that, but I think it's
> doable.
>
> Obviously we also need to have a generic binding for a "parent
> domain". I like Geert's proposal from the other patch, which means
> using "power-domains = <&pd_xyz>".
>
> Kind regards
> Uffe
>
> [1]
> http://marc.info/?l=linux-pm&m=141709766008458&w=2
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