summaryrefslogtreecommitdiffstats
path: root/kernel/Documentation/devicetree/bindings/arm/psci.txt
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/Documentation/devicetree/bindings/arm/psci.txt')
-rw-r--r--kernel/Documentation/devicetree/bindings/arm/psci.txt102
1 files changed, 102 insertions, 0 deletions
diff --git a/kernel/Documentation/devicetree/bindings/arm/psci.txt b/kernel/Documentation/devicetree/bindings/arm/psci.txt
new file mode 100644
index 000000000..5aa40ede0
--- /dev/null
+++ b/kernel/Documentation/devicetree/bindings/arm/psci.txt
@@ -0,0 +1,102 @@
+* Power State Coordination Interface (PSCI)
+
+Firmware implementing the PSCI functions described in ARM document number
+ARM DEN 0022A ("Power State Coordination Interface System Software on ARM
+processors") can be used by Linux to initiate various CPU-centric power
+operations.
+
+Issue A of the specification describes functions for CPU suspend, hotplug
+and migration of secure software.
+
+Functions are invoked by trapping to the privilege level of the PSCI
+firmware (specified as part of the binding below) and passing arguments
+in a manner similar to that specified by AAPCS:
+
+ r0 => 32-bit Function ID / return value
+ {r1 - r3} => Parameters
+
+Note that the immediate field of the trapping instruction must be set
+to #0.
+
+
+Main node required properties:
+
+ - compatible : should contain at least one of:
+
+ * "arm,psci" : for implementations complying to PSCI versions prior to
+ 0.2. For these cases function IDs must be provided.
+
+ * "arm,psci-0.2" : for implementations complying to PSCI 0.2. Function
+ IDs are not required and should be ignored by an OS with PSCI 0.2
+ support, but are permitted to be present for compatibility with
+ existing software when "arm,psci" is later in the compatible list.
+
+ - method : The method of calling the PSCI firmware. Permitted
+ values are:
+
+ "smc" : SMC #0, with the register assignments specified
+ in this binding.
+
+ "hvc" : HVC #0, with the register assignments specified
+ in this binding.
+
+Main node optional properties:
+
+ - cpu_suspend : Function ID for CPU_SUSPEND operation
+
+ - cpu_off : Function ID for CPU_OFF operation
+
+ - cpu_on : Function ID for CPU_ON operation
+
+ - migrate : Function ID for MIGRATE operation
+
+Device tree nodes that require usage of PSCI CPU_SUSPEND function (ie idle
+state nodes, as per bindings in [1]) must specify the following properties:
+
+- arm,psci-suspend-param
+ Usage: Required for state nodes[1] if the corresponding
+ idle-states node entry-method property is set
+ to "psci".
+ Value type: <u32>
+ Definition: power_state parameter to pass to the PSCI
+ suspend call.
+
+Example:
+
+Case 1: PSCI v0.1 only.
+
+ psci {
+ compatible = "arm,psci";
+ method = "smc";
+ cpu_suspend = <0x95c10000>;
+ cpu_off = <0x95c10001>;
+ cpu_on = <0x95c10002>;
+ migrate = <0x95c10003>;
+ };
+
+Case 2: PSCI v0.2 only
+
+ psci {
+ compatible = "arm,psci-0.2";
+ method = "smc";
+ };
+
+Case 3: PSCI v0.2 and PSCI v0.1.
+
+ A DTB may provide IDs for use by kernels without PSCI 0.2 support,
+ enabling firmware and hypervisors to support existing and new kernels.
+ These IDs will be ignored by kernels with PSCI 0.2 support, which will
+ use the standard PSCI 0.2 IDs exclusively.
+
+ psci {
+ compatible = "arm,psci-0.2", "arm,psci";
+ method = "hvc";
+
+ cpu_on = < arbitrary value >;
+ cpu_off = < arbitrary value >;
+
+ ...
+ };
+
+[1] Kernel documentation - ARM idle states bindings
+ Documentation/devicetree/bindings/arm/idle-states.txt