projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 65397edf WD |
1 | * Power State Coordination Interface (PSCI) |
| 2 | ||
| 3 | Firmware implementing the PSCI functions described in ARM document number | |
| 4 | ARM DEN 0022A ("Power State Coordination Interface System Software on ARM | |
| 5 | processors") can be used by Linux to initiate various CPU-centric power | |
| 6 | operations. | |
| 7 | ||
| 8 | Issue A of the specification describes functions for CPU suspend, hotplug | |
| 9 | and migration of secure software. | |
| 10 | ||
| 11 | Functions are invoked by trapping to the privilege level of the PSCI | |
| 12 | firmware (specified as part of the binding below) and passing arguments | |
| 13 | in a manner similar to that specified by AAPCS: | |
| 14 | ||
| 15 | r0 => 32-bit Function ID / return value | |
| 16 | {r1 - r3} => Parameters | |
| 17 | ||
| 18 | Note that the immediate field of the trapping instruction must be set | |
| 19 | to #0. | |
| 20 | ||
| 21 | ||
| 22 | Main node required properties: | |
| 23 | ||
| e1cd3b36 AC |
24 | - 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. | |
| 65397edf WD |
33 | |
| 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 | ||
| 43 | Main 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 | ||
| 3f8161b2 LP |
53 | Device tree nodes that require usage of PSCI CPU_SUSPEND function (ie idle |
| 54 | state 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. | |
| 65397edf WD |
63 | |
| 64 | Example: | |
| 65 | ||
| e1cd3b36 AC |
66 | Case 1: PSCI v0.1 only. |
| 67 | ||
| 65397edf WD |
68 | psci { |
| 69 | compatible = "arm,psci"; | |
| 70 | method = "smc"; | |
| 71 | cpu_suspend = <0x95c10000>; | |
| 72 | cpu_off = <0x95c10001>; | |
| 73 | cpu_on = <0x95c10002>; | |
| 74 | migrate = <0x95c10003>; | |
| 75 | }; | |
| e1cd3b36 | 76 | |
| e1cd3b36 AC |
77 | Case 2: PSCI v0.2 only |
| 78 | ||
| 79 | psci { | |
| 80 | compatible = "arm,psci-0.2"; | |
| 81 | method = "smc"; | |
| 82 | }; | |
| 83 | ||
| 84 | Case 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 | }; | |
| 3f8161b2 LP |
100 | |
| 101 | [1] Kernel documentation - ARM idle states bindings | |
| 102 | Documentation/devicetree/bindings/arm/idle-states.txt |