The RISC-V CPU idle states will be described in DT under the /cpus/riscv-idle-states DT node. This patch adds the bindings documentation for riscv-idle-states DT nodes and idle state DT nodes under it. Signed-off-by: Anup Patel <anup.patel@xxxxxxx> --- .../bindings/riscv/idle-states.yaml | 250 ++++++++++++++++++ 1 file changed, 250 insertions(+) create mode 100644 Documentation/devicetree/bindings/riscv/idle-states.yaml diff --git a/Documentation/devicetree/bindings/riscv/idle-states.yaml b/Documentation/devicetree/bindings/riscv/idle-states.yaml new file mode 100644 index 000000000000..3eff763fed23 --- /dev/null +++ b/Documentation/devicetree/bindings/riscv/idle-states.yaml @@ -0,0 +1,250 @@ +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) +%YAML 1.2 +--- +$id: http://devicetree.org/schemas/riscv/idle-states.yaml# +$schema: http://devicetree.org/meta-schemas/core.yaml# + +title: RISC-V idle states binding description + +maintainers: + - Anup Patel <anup.patel@xxxxxxx> + +description: |+ + RISC-V systems can manage power consumption dynamically, where HARTs + (or CPUs) [1] can be put in different platform specific suspend (or + idle) states (ranging from simple WFI, power gating, etc). The RISC-V + SBI [2] hart state management extension provides a standard mechanism + for OSes to request HART state transitions. + + The platform specific suspend (or idle) states of a hart can be either + retentive or non-rententive in nature. A retentive suspend state will + preserve hart register and CSR values for all privilege modes whereas + a non-retentive suspend state will not preserve hart register and CSR + values. The suspend (or idle) state entered by executing the WFI + instruction is considered standard on all RISC-V systems and therefore + must not be listed in device tree. + + The device tree binding definition for RISC-V idle states described + in this document is quite similar to the ARM idle states [3]. + + References + + [1] RISC-V Linux Kernel documentation - CPUs bindings + Documentation/devicetree/bindings/riscv/cpus.yaml + + [2] RISC-V Supervisor Binary Interface (SBI) + http://github.com/riscv/riscv-sbi-doc/riscv-sbi.adoc + + [3] ARM idle states binding description - Idle states bindings + Documentation/devicetree/bindings/arm/idle-states.yaml + +properties: + $nodename: + const: riscv-idle-states + +patternProperties: + "^(cpu|cluster)-": + type: object + description: | + Each state node represents an idle state description and must be + defined as follows. + + properties: + compatible: + const: riscv,idle-state + + local-timer-stop: + description: + If present the CPU local timer control logic is lost on state + entry, otherwise it is retained. + type: boolean + + entry-latency-us: + description: + Worst case latency in microseconds required to enter the idle state. + + exit-latency-us: + description: + Worst case latency in microseconds required to exit the idle state. + The exit-latency-us duration may be guaranteed only after + entry-latency-us has passed. + + min-residency-us: + description: + Minimum residency duration in microseconds, inclusive of preparation + and entry, for this idle state to be considered worthwhile energy + wise (refer to section 2 of this document for a complete description). + + wakeup-latency-us: + description: | + Maximum delay between the signaling of a wake-up event and the CPU + being able to execute normal code again. If omitted, this is assumed + to be equal to: + + entry-latency-us + exit-latency-us + + It is important to supply this value on systems where the duration + of PREP phase (see diagram 1, section 2) is non-neglibigle. In such + systems entry-latency-us + exit-latency-us will exceed + wakeup-latency-us by this duration. + + idle-state-name: + $ref: /schemas/types.yaml#/definitions/string + description: + A string used as a descriptive name for the idle state. + + required: + - compatible + - entry-latency-us + - exit-latency-us + - min-residency-us + +additionalProperties: false + +examples: + - | + + cpus { + #size-cells = <0>; + #address-cells = <1>; + + cpu@0 { + device_type = "cpu"; + compatible = "riscv"; + reg = <0x0>; + riscv,isa = "rv64imafdc"; + mmu-type = "riscv,sv48"; + cpu-idle-states = <&CPU_RET_0_0 &CPU_NONRET_0_0 + &CLUSTER_RET_0 &CLUSTER_NONRET_0>; + + cpu_intc0: interrupt-controller { + #interrupt-cells = <1>; + compatible = "riscv,cpu-intc"; + interrupt-controller; + }; + }; + + cpu@1 { + device_type = "cpu"; + compatible = "riscv"; + reg = <0x1>; + riscv,isa = "rv64imafdc"; + mmu-type = "riscv,sv48"; + cpu-idle-states = <&CPU_RET_0_0 &CPU_NONRET_0_0 + &CLUSTER_RET_0 &CLUSTER_NONRET_0>; + + cpu_intc1: interrupt-controller { + #interrupt-cells = <1>; + compatible = "riscv,cpu-intc"; + interrupt-controller; + }; + }; + + cpu@10 { + device_type = "cpu"; + compatible = "riscv"; + reg = <0x10>; + riscv,isa = "rv64imafdc"; + mmu-type = "riscv,sv48"; + cpu-idle-states = <&CPU_RET_1_0 &CPU_NONRET_1_0 + &CLUSTER_RET_1 &CLUSTER_NONRET_1>; + + cpu_intc10: interrupt-controller { + #interrupt-cells = <1>; + compatible = "riscv,cpu-intc"; + interrupt-controller; + }; + }; + + cpu@11 { + device_type = "cpu"; + compatible = "riscv"; + reg = <0x11>; + riscv,isa = "rv64imafdc"; + mmu-type = "riscv,sv48"; + cpu-idle-states = <&CPU_RET_1_0 &CPU_NONRET_1_0 + &CLUSTER_RET_1 &CLUSTER_NONRET_1>; + + cpu_intc11: interrupt-controller { + #interrupt-cells = <1>; + compatible = "riscv,cpu-intc"; + interrupt-controller; + }; + }; + + riscv-idle-states { + CPU_RET_0_0: cpu-retentive-0-0 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x10000000>; + entry-latency-us = <20>; + exit-latency-us = <40>; + min-residency-us = <80>; + }; + + CPU_NONRET_0_0: cpu-nonretentive-0-0 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x90000000>; + entry-latency-us = <250>; + exit-latency-us = <500>; + min-residency-us = <950>; + }; + + CLUSTER_RET_0: cluster-retentive-0 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x11000000>; + local-timer-stop; + entry-latency-us = <50>; + exit-latency-us = <100>; + min-residency-us = <250>; + wakeup-latency-us = <130>; + }; + + CLUSTER_NONRET_0: cluster-nonretentive-0 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x91000000>; + local-timer-stop; + entry-latency-us = <600>; + exit-latency-us = <1100>; + min-residency-us = <2700>; + wakeup-latency-us = <1500>; + }; + + CPU_RET_1_0: cpu-retentive-1-0 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x10000010>; + entry-latency-us = <20>; + exit-latency-us = <40>; + min-residency-us = <80>; + }; + + CPU_NONRET_1_0: cpu-nonretentive-1-0 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x90000010>; + entry-latency-us = <250>; + exit-latency-us = <500>; + min-residency-us = <950>; + }; + + CLUSTER_RET_1: cluster-retentive-1 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x11000010>; + local-timer-stop; + entry-latency-us = <50>; + exit-latency-us = <100>; + min-residency-us = <250>; + wakeup-latency-us = <130>; + }; + + CLUSTER_NONRET_1: cluster-nonretentive-1 { + compatible = "riscv,idle-state"; + riscv,sbi-suspend-param = <0x91000010>; + local-timer-stop; + entry-latency-us = <600>; + exit-latency-us = <1100>; + min-residency-us = <2700>; + wakeup-latency-us = <1500>; + }; + }; + }; + +... -- 2.25.1
