linux-kernel - Re: [PATCH v2 01/11] base: power: Add generic OF-based power domain look-up

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Message-ID: <7e54f23f-1e11-4e17-ad29-13b497d7055a@TX2EHSMHS041.ehs.local>
Date:	Wed, 19 Mar 2014 16:13:41 -0700
From:	Sören Brinkmann <soren.brinkmann@...inx.com>
To:	Tomasz Figa <tomasz.figa@...il.com>
CC:	<linux-pm@...r.kernel.org>, Mark Rutland <mark.rutland@....com>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Len Brown <len.brown@...el.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Tomasz Figa <t.figa@...sung.com>, Pavel Machek <pavel@....cz>,
	Kukjin Kim <kgene.kim@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	<linux-samsung-soc@...r.kernel.org>,
	Russell King <linux@....linux.org.uk>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	<devicetree@...r.kernel.org>, Pawel Moll <pawel.moll@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Rob Herring <robh+dt@...nel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	<linux-kernel@...r.kernel.org>, Mark Brown <broonie@...nel.org>,
	Kumar Gala <galak@...eaurora.org>
Subject: Re: [PATCH v2 01/11] base: power: Add generic OF-based power domain
 look-up

On Mon, 2014-03-03 at 05:02PM +0100, 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.
> 
> Signed-off-by: Tomasz Figa <tomasz.figa@...il.com>
> ---
>  .../devicetree/bindings/power/power_domain.txt     |  51 ++++
>  drivers/base/power/domain.c                        | 298 +++++++++++++++++++++
>  include/linux/pm_domain.h                          |  46 ++++
>  kernel/power/Kconfig                               |   4 +
>  4 files changed, 399 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/power/power_domain.txt
> 
> diff --git a/Documentation/devicetree/bindings/power/power_domain.txt b/Documentation/devicetree/bindings/power/power_domain.txt
> new file mode 100644
> index 0000000..93be5d9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/power/power_domain.txt
> @@ -0,0 +1,51 @@
> +* Generic power domains
> +
> +System on chip designs are often divided into multiple power domains that
> +can be used for power gating of selected IP blocks for power saving by
> +reduced leakage current.
> +
> +This device tree binding can be used to bind power domain consumer devices
> +with their power domains provided by power domain providers. A power domain
> +provider can be represented by any node in the device tree and can provide
> +one or more power domains. A consumer node can refer to the provider by
> +a phandle and a set of phandle arguments (so called power domain specifier)
> +of length specified by #power-domain-cells property in the power domain
> +provider node.
> +
> +==Power domain providers==
> +
> +Required properties:
> + - #power-domain-cells : Number of cells in a power domain specifier;
> +   Typically 0 for nodes representing a single power domain and 1 for nodes
> +   providing multiple power domains (e.g. power controllers), but can be
> +   any value as specified by device tree binding documentation of particular
> +   provider.
> +
> +Example:
> +
> +	power: power-controller@...40000 {
> +		compatible = "foo,power-controller";
> +		reg = <0x12340000 0x1000>;
> +		#power-domain-cells = <1>;
> +	};
> +
> +The node above defines a power controller that is a power domain provider
> +and expects one cell as its phandle argument.
> +
> +==Power domain consumers==
> +
> +Required properties:
> + - power-domain : A phandle and power domain specifier as defined by bindings
> +                  of power controller specified by phandle.
> +
> +Example:
> +
> +	leaky-device@...50000 {
> +		compatible = "foo,i-leak-current";
> +		reg = <0x12350000 0x1000>;
> +		power-domain = <&power 0>;
> +	};
> +
> +The node above defines a typical power domain consumer device, which is located
> +inside power domain with index 0 of power controller represented by node with
> +label "power".

Does this allow nesting of power domains? E.g. you have a PD which is
represented by some programmable power supply, and within this domain
smaller islands/domains that can be gated independently.

	Thanks,
	Sören


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