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Diffstat (limited to 'dts/Bindings/arm/msm/qcom,idle-state.txt')
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diff --git a/dts/Bindings/arm/msm/qcom,idle-state.txt b/dts/Bindings/arm/msm/qcom,idle-state.txt deleted file mode 100644 index 06df04cc82..0000000000 --- a/dts/Bindings/arm/msm/qcom,idle-state.txt +++ /dev/null @@ -1,84 +0,0 @@ -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/arm/idle-states.txt |