blob: 5aa40ede0e99337d9c66b4b45ccf2cb7c1cd0e93 [file] [log] [blame]
Will Deacon65397ed2012-12-11 17:28:27 +00001* Power State Coordination Interface (PSCI)
2
3Firmware implementing the PSCI functions described in ARM document number
4ARM DEN 0022A ("Power State Coordination Interface System Software on ARM
5processors") can be used by Linux to initiate various CPU-centric power
6operations.
7
8Issue A of the specification describes functions for CPU suspend, hotplug
9and migration of secure software.
10
11Functions are invoked by trapping to the privilege level of the PSCI
12firmware (specified as part of the binding below) and passing arguments
13in a manner similar to that specified by AAPCS:
14
15 r0 => 32-bit Function ID / return value
16 {r1 - r3} => Parameters
17
18Note that the immediate field of the trapping instruction must be set
19to #0.
20
21
22Main node required properties:
23
Ashwin Chaugulee1cd3b32014-03-27 11:08:57 -040024 - compatible : should contain at least one of:
25
26 * "arm,psci" : for implementations complying to PSCI versions prior to
27 0.2. For these cases function IDs must be provided.
28
29 * "arm,psci-0.2" : for implementations complying to PSCI 0.2. Function
30 IDs are not required and should be ignored by an OS with PSCI 0.2
31 support, but are permitted to be present for compatibility with
32 existing software when "arm,psci" is later in the compatible list.
Will Deacon65397ed2012-12-11 17:28:27 +000033
34 - method : The method of calling the PSCI firmware. Permitted
35 values are:
36
37 "smc" : SMC #0, with the register assignments specified
38 in this binding.
39
40 "hvc" : HVC #0, with the register assignments specified
41 in this binding.
42
43Main node optional properties:
44
45 - cpu_suspend : Function ID for CPU_SUSPEND operation
46
47 - cpu_off : Function ID for CPU_OFF operation
48
49 - cpu_on : Function ID for CPU_ON operation
50
51 - migrate : Function ID for MIGRATE operation
52
Lorenzo Pieralisi3f8161b2013-11-27 16:22:55 +000053Device tree nodes that require usage of PSCI CPU_SUSPEND function (ie idle
54state nodes, as per bindings in [1]) must specify the following properties:
55
56- arm,psci-suspend-param
57 Usage: Required for state nodes[1] if the corresponding
58 idle-states node entry-method property is set
59 to "psci".
60 Value type: <u32>
61 Definition: power_state parameter to pass to the PSCI
62 suspend call.
Will Deacon65397ed2012-12-11 17:28:27 +000063
64Example:
65
Ashwin Chaugulee1cd3b32014-03-27 11:08:57 -040066Case 1: PSCI v0.1 only.
67
Will Deacon65397ed2012-12-11 17:28:27 +000068 psci {
69 compatible = "arm,psci";
70 method = "smc";
71 cpu_suspend = <0x95c10000>;
72 cpu_off = <0x95c10001>;
73 cpu_on = <0x95c10002>;
74 migrate = <0x95c10003>;
75 };
Ashwin Chaugulee1cd3b32014-03-27 11:08:57 -040076
Ashwin Chaugulee1cd3b32014-03-27 11:08:57 -040077Case 2: PSCI v0.2 only
78
79 psci {
80 compatible = "arm,psci-0.2";
81 method = "smc";
82 };
83
84Case 3: PSCI v0.2 and PSCI v0.1.
85
86 A DTB may provide IDs for use by kernels without PSCI 0.2 support,
87 enabling firmware and hypervisors to support existing and new kernels.
88 These IDs will be ignored by kernels with PSCI 0.2 support, which will
89 use the standard PSCI 0.2 IDs exclusively.
90
91 psci {
92 compatible = "arm,psci-0.2", "arm,psci";
93 method = "hvc";
94
95 cpu_on = < arbitrary value >;
96 cpu_off = < arbitrary value >;
97
98 ...
99 };
Lorenzo Pieralisi3f8161b2013-11-27 16:22:55 +0000100
101[1] Kernel documentation - ARM idle states bindings
102 Documentation/devicetree/bindings/arm/idle-states.txt