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

[Tomasz Figa]

Hi SÃren,

On 20.03.2014 00:13, SÃren Brinkmann wrote:
> 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@xxxxxxxxx>
> > ---
> >   .../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@12340000 {
> > +		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@12350000 {
> > +		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.

These are client-side bindings only, i.e. power domain providers and 
consumers. Registering power domains and relations between them are up 
to platform-specific code, e.g. power controller driver.

Best regards,
Tomasz
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