1* Generic PM domains
2
3System on chip designs are often divided into multiple PM domains that can be
4used for power gating of selected IP blocks for power saving by reduced leakage
5current.
6
7This device tree binding can be used to bind PM domain consumer devices with
8their PM domains provided by PM domain providers. A PM domain provider can be
9represented by any node in the device tree and can provide one or more PM
10domains. A consumer node can refer to the provider by a phandle and a set of
11phandle arguments (so called PM domain specifiers) of length specified by the
12#power-domain-cells property in the PM domain provider node.
13
14==PM domain providers==
15
16Required properties:
17 - #power-domain-cells : Number of cells in a PM domain specifier;
18   Typically 0 for nodes representing a single PM domain and 1 for nodes
19   providing multiple PM domains (e.g. power controllers), but can be any value
20   as specified by device tree binding documentation of particular provider.
21
22Optional properties:
23 - power-domains : A phandle and PM domain specifier as defined by bindings of
24                   the power controller specified by phandle.
25   Some power domains might be powered from another power domain (or have
26   other hardware specific dependencies). For representing such dependency
27   a standard PM domain consumer binding is used. When provided, all domains
28   created by the given provider should be subdomains of the domain
29   specified by this binding. More details about power domain specifier are
30   available in the next section.
31
32- domain-idle-states : A phandle of an idle-state that shall be soaked into a
33                generic domain power state. The idle state definitions are
34                compatible with domain-idle-state specified in [1]. phandles
35                that are not compatible with domain-idle-state will be
36                ignored.
37  The domain-idle-state property reflects the idle state of this PM domain and
38  not the idle states of the devices or sub-domains in the PM domain. Devices
39  and sub-domains have their own idle-states independent of the parent
40  domain's idle states. In the absence of this property, the domain would be
41  considered as capable of being powered-on or powered-off.
42
43Example:
44
45	power: power-controller@12340000 {
46		compatible = "foo,power-controller";
47		reg = <0x12340000 0x1000>;
48		#power-domain-cells = <1>;
49	};
50
51The node above defines a power controller that is a PM domain provider and
52expects one cell as its phandle argument.
53
54Example 2:
55
56	parent: power-controller@12340000 {
57		compatible = "foo,power-controller";
58		reg = <0x12340000 0x1000>;
59		#power-domain-cells = <1>;
60	};
61
62	child: power-controller@12341000 {
63		compatible = "foo,power-controller";
64		reg = <0x12341000 0x1000>;
65		power-domains = <&parent 0>;
66		#power-domain-cells = <1>;
67	};
68
69The nodes above define two power controllers: 'parent' and 'child'.
70Domains created by the 'child' power controller are subdomains of '0' power
71domain provided by the 'parent' power controller.
72
73Example 3:
74	parent: power-controller@12340000 {
75		compatible = "foo,power-controller";
76		reg = <0x12340000 0x1000>;
77		#power-domain-cells = <0>;
78		domain-idle-states = <&DOMAIN_RET>, <&DOMAIN_PWR_DN>;
79	};
80
81	child: power-controller@12341000 {
82		compatible = "foo,power-controller";
83		reg = <0x12341000 0x1000>;
84		power-domains = <&parent>;
85		#power-domain-cells = <0>;
86		domain-idle-states = <&DOMAIN_PWR_DN>;
87	};
88
89	DOMAIN_RET: state@0 {
90		compatible = "domain-idle-state";
91		reg = <0x0>;
92		entry-latency-us = <1000>;
93		exit-latency-us = <2000>;
94		min-residency-us = <10000>;
95	};
96
97	DOMAIN_PWR_DN: state@1 {
98		compatible = "domain-idle-state";
99		reg = <0x1>;
100		entry-latency-us = <5000>;
101		exit-latency-us = <8000>;
102		min-residency-us = <7000>;
103	};
104
105==PM domain consumers==
106
107Required properties:
108 - power-domains : A phandle and PM domain specifier as defined by bindings of
109                   the power controller specified by phandle.
110
111Example:
112
113	leaky-device@12350000 {
114		compatible = "foo,i-leak-current";
115		reg = <0x12350000 0x1000>;
116		power-domains = <&power 0>;
117	};
118
119The node above defines a typical PM domain consumer device, which is located
120inside a PM domain with index 0 of a power controller represented by a node
121with the label "power".
122
123[1]. Documentation/devicetree/bindings/power/domain-idle-state.txt
124