Re: [PATCH v3 1/3] base: power: Add generic OF-based power domain look-up

From: Ulf Hansson <ulf.hansson@linaro.org>
To: Stephen Warren <swarren@wwwdotorg.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Philipp Zabel <philipp.zabel@gmail.com>,
	Len Brown <len.brown@intel.com>,
	Stephen Boyd <sboyd@codeaurora.org>,
	Tomasz Figa <t.figa@samsung.com>,
	Tomasz Figa <tomasz.figa@gmail.com>, Pavel Machek <pavel@ucw.cz>,
	Kukjin Kim <kgene.kim@samsung.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	linux-samsung-soc <linux-samsung-soc@vger.kernel.org>,
	Russell King <linux@arm.linux.org.uk>,
	Ian Campbell <ijc+devicetree@hellion.org.uk>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	Kevin Hilman <khilman@linaro.org>,
	Pawel Moll <pawel.moll@arm.com>,
	"linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Rafael J. Wysocki
Subject: Re: [PATCH v3 1/3] base: power: Add generic OF-based power domain look-up
Date: Tue, 6 May 2014 10:22:42 +0200	[thread overview]
Message-ID: <CAPDyKFoGOcScsaGWkw9bVh=gpGTApRK48AczaMiSmLah+YOSXQ@mail.gmail.com> (raw)
In-Reply-To: <535E9163.3070305@wwwdotorg.org>

On 28 April 2014 19:35, Stephen Warren <swarren@wwwdotorg.org> wrote:
> On 04/23/2014 10:46 AM, Tomasz Figa wrote:
>> 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.
>
>> diff --git a/Documentation/devicetree/bindings/power/power_domain.txt b/Documentation/devicetree/bindings/power/power_domain.txt
>
>> +==Power domain consumers==
>> +
>> +Required properties:
>> + - power-domain : A phandle and power domain specifier as defined by bindings
>> +                  of power controller specified by phandle.
>
> It seems quite likely that a single logical device could have components
> in multiple power domains. Consider an HDMI controller with different
> power domains for the HDMI core, CEC communication, DDC/I2C
> communication, and the I/O pads, with no clear separation between those
> two components of the module (no separate register spaces, but the
> bits/registers are interleaved all together).
>
> As such, I think that rather than a "power-domain" property, we need a
> pair of "power-domains", and "power-domain-names" properties, and
> preferably with mandatory usage of name-based lookups, rather than
> allowing a random mix of name-based and index-based lookups like we have
> with some existing resource bindings.

Each struct device have only one dev_pm_domain pointer, thus a device
are not able to reside in more than one power domain.

Therefore I doubt this will be very useful, unless I missed your point. :-)

Kind regards
Ulf Hansson