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-rw-r--r--Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt84
-rw-r--r--Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt58
2 files changed, 142 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
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+QCOM Idle States for cpuidle driver
+
+ARM provides idle-state node to define the cpuidle states, as defined in [1].
+cpuidle-qcom is the cpuidle driver for Qualcomm SoCs and uses these idle
+states. Idle states have different enter/exit latency and residency values.
+The idle states supported by the QCOM SoC are defined as -
+
+ * Standby
+ * Retention
+ * Standalone Power Collapse (Standalone PC or SPC)
+ * Power Collapse (PC)
+
+Standby: Standby does a little more in addition to architectural clock gating.
+When the WFI instruction is executed the ARM core would gate its internal
+clocks. In addition to gating the clocks, QCOM cpus use this instruction as a
+trigger to execute the SPM state machine. The SPM state machine waits for the
+interrupt to trigger the core back in to active. This triggers the cache
+hierarchy to enter standby states, when all cpus are idle. An interrupt brings
+the SPM state machine out of its wait, the next step is to ensure that the
+cache hierarchy is also out of standby, and then the cpu is allowed to resume
+execution. This state is defined as a generic ARM WFI state by the ARM cpuidle
+driver and is not defined in the DT. The SPM state machine should be
+configured to execute this state by default and after executing every other
+state below.
+
+Retention: Retention is a low power state where the core is clock gated and
+the memory and the registers associated with the core are retained. The
+voltage may be reduced to the minimum value needed to keep the processor
+registers active. The SPM should be configured to execute the retention
+sequence and would wait for interrupt, before restoring the cpu to execution
+state. Retention may have a slightly higher latency than Standby.
+
+Standalone PC: A cpu can power down and warmboot if there is a sufficient time
+between the time it enters idle and the next known wake up. SPC mode is used
+to indicate a core entering a power down state without consulting any other
+cpu or the system resources. This helps save power only on that core. The SPM
+sequence for this idle state is programmed to power down the supply to the
+core, wait for the interrupt, restore power to the core, and ensure the
+system state including cache hierarchy is ready before allowing core to
+resume. Applying power and resetting the core causes the core to warmboot
+back into Elevation Level (EL) which trampolines the control back to the
+kernel. Entering a power down state for the cpu, needs to be done by trapping
+into a EL. Failing to do so, would result in a crash enforced by the warm boot
+code in the EL for the SoC. On SoCs with write-back L1 cache, the cache has to
+be flushed in s/w, before powering down the core.
+
+Power Collapse: This state is similar to the SPC mode, but distinguishes
+itself in that the cpu acknowledges and permits the SoC to enter deeper sleep
+modes. In a hierarchical power domain SoC, this means L2 and other caches can
+be flushed, system bus, clocks - lowered, and SoC main XO clock gated and
+voltages reduced, provided all cpus enter this state. Since the span of low
+power modes possible at this state is vast, the exit latency and the residency
+of this low power mode would be considered high even though at a cpu level,
+this essentially is cpu power down. The SPM in this state also may handshake
+with the Resource power manager (RPM) processor in the SoC to indicate a
+complete application processor subsystem shut down.
+
+The idle-state for QCOM SoCs are distinguished by the compatible property of
+the idle-states device node.
+
+The devicetree representation of the idle state should be -
+
+Required properties:
+
+- compatible: Must be one of -
+ "qcom,idle-state-ret",
+ "qcom,idle-state-spc",
+ "qcom,idle-state-pc",
+ and "arm,idle-state".
+
+Other required and optional properties are specified in [1].
+
+Example:
+
+ idle-states {
+ CPU_SPC: spc {
+ compatible = "qcom,idle-state-spc", "arm,idle-state";
+ entry-latency-us = <150>;
+ exit-latency-us = <200>;
+ min-residency-us = <2000>;
+ };
+ };
+
+[1]. Documentation/devicetree/bindings/cpu/idle-states.yaml
diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt b/Documentation/devicetree/bindings/arm/msm/qcom,saw2.txt
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+SPM AVS Wrapper 2 (SAW2)
+
+The SAW2 is a wrapper around the Subsystem Power Manager (SPM) and the
+Adaptive Voltage Scaling (AVS) hardware. The SPM is a programmable
+power-controller that transitions a piece of hardware (like a processor or
+subsystem) into and out of low power modes via a direct connection to
+the PMIC. It can also be wired up to interact with other processors in the
+system, notifying them when a low power state is entered or exited.
+
+Multiple revisions of the SAW hardware are supported using these Device Nodes.
+SAW2 revisions differ in the register offset and configuration data. Also, the
+same revision of the SAW in different SoCs may have different configuration
+data due the differences in hardware capabilities. Hence the SoC name, the
+version of the SAW hardware in that SoC and the distinction between cpu (big
+or Little) or cache, may be needed to uniquely identify the SAW register
+configuration and initialization data. The compatible string is used to
+indicate this parameter.
+
+PROPERTIES
+
+- compatible:
+ Usage: required
+ Value type: <string>
+ Definition: Must have
+ "qcom,saw2"
+ A more specific value could be one of:
+ "qcom,apq8064-saw2-v1.1-cpu"
+ "qcom,msm8226-saw2-v2.1-cpu"
+ "qcom,msm8974-saw2-v2.1-cpu"
+ "qcom,apq8084-saw2-v2.1-cpu"
+
+- reg:
+ Usage: required
+ Value type: <prop-encoded-array>
+ Definition: the first element specifies the base address and size of
+ the register region. An optional second element specifies
+ the base address and size of the alias register region.
+
+- regulator:
+ Usage: optional
+ Value type: boolean
+ Definition: Indicates that this SPM device acts as a regulator device
+ device for the core (CPU or Cache) the SPM is attached
+ to.
+
+Example 1:
+
+ power-controller@2099000 {
+ compatible = "qcom,saw2";
+ reg = <0x02099000 0x1000>, <0x02009000 0x1000>;
+ regulator;
+ };
+
+Example 2:
+ saw0: power-controller@f9089000 {
+ compatible = "qcom,apq8084-saw2-v2.1-cpu", "qcom,saw2";
+ reg = <0xf9089000 0x1000>, <0xf9009000 0x1000>;
+ };