Re: [PATCH v10 7/8] dt-bindings: Add common bindings for ARM and RISC-V idle states

[Guo Ren]

Acked-by: Guo Ren <guoren@xxxxxxxxxx>

On Wed, Jan 26, 2022 at 7:50 PM Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:
>
> From: Anup Patel <anup.patel@xxxxxxx>
>
> The RISC-V CPU idle states will be described in under the
> /cpus/idle-states DT node in the same way as ARM CPU idle
> states.
>
> This patch adds common bindings documentation for both ARM
> and RISC-V idle states.
>
> Signed-off-by: Anup Patel <anup.patel@xxxxxxx>
> Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> ---
>  .../bindings/arm/msm/qcom,idle-state.txt      |   2 +-
>  .../devicetree/bindings/arm/psci.yaml         |   2 +-
>  .../bindings/{arm => cpu}/idle-states.yaml    | 228 ++++++++++++++++--
>  .../devicetree/bindings/riscv/cpus.yaml       |   6 +
>  4 files changed, 219 insertions(+), 19 deletions(-)
>  rename Documentation/devicetree/bindings/{arm => cpu}/idle-states.yaml (74%)
>
> diff --git a/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
> index 6ce0b212ec6d..606b4b1b709d 100644
> --- a/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
> +++ b/Documentation/devicetree/bindings/arm/msm/qcom,idle-state.txt
> @@ -81,4 +81,4 @@ Example:
>                 };
>         };
>
> -[1]. Documentation/devicetree/bindings/arm/idle-states.yaml
> +[1]. Documentation/devicetree/bindings/cpu/idle-states.yaml
> diff --git a/Documentation/devicetree/bindings/arm/psci.yaml b/Documentation/devicetree/bindings/arm/psci.yaml
> index 8b77cf83a095..dd83ef278af0 100644
> --- a/Documentation/devicetree/bindings/arm/psci.yaml
> +++ b/Documentation/devicetree/bindings/arm/psci.yaml
> @@ -101,7 +101,7 @@ properties:
>        bindings in [1]) must specify this property.
>
>        [1] Kernel documentation - ARM idle states bindings
> -        Documentation/devicetree/bindings/arm/idle-states.yaml
> +        Documentation/devicetree/bindings/cpu/idle-states.yaml
>
>  patternProperties:
>    "^power-domain-":
> diff --git a/Documentation/devicetree/bindings/arm/idle-states.yaml b/Documentation/devicetree/bindings/cpu/idle-states.yaml
> similarity index 74%
> rename from Documentation/devicetree/bindings/arm/idle-states.yaml
> rename to Documentation/devicetree/bindings/cpu/idle-states.yaml
> index 52bce5dbb11f..95506ffb816c 100644
> --- a/Documentation/devicetree/bindings/arm/idle-states.yaml
> +++ b/Documentation/devicetree/bindings/cpu/idle-states.yaml
> @@ -1,25 +1,30 @@
>  # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>  %YAML 1.2
>  ---
> -$id: http://devicetree.org/schemas/arm/idle-states.yaml#
> +$id: http://devicetree.org/schemas/cpu/idle-states.yaml#
>  $schema: http://devicetree.org/meta-schemas/core.yaml#
>
> -title: ARM idle states binding description
> +title: Idle states binding description
>
>  maintainers:
>    - Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> +  - Anup Patel <anup@xxxxxxxxxxxxxx>
>
>  description: |+
>    ==========================================
>    1 - Introduction
>    ==========================================
>
> -  ARM systems contain HW capable of managing power consumption dynamically,
> -  where cores can be put in different low-power states (ranging from simple wfi
> -  to power gating) according to OS PM policies. The CPU states representing the
> -  range of dynamic idle states that a processor can enter at run-time, can be
> -  specified through device tree bindings representing the parameters required to
> -  enter/exit specific idle states on a given processor.
> +  ARM and RISC-V systems contain HW capable of managing power consumption
> +  dynamically, where cores can be put in different low-power states (ranging
> +  from simple wfi to power gating) according to OS PM policies. The CPU states
> +  representing the range of dynamic idle states that a processor can enter at
> +  run-time, can be specified through device tree bindings representing the
> +  parameters required to enter/exit specific idle states on a given processor.
> +
> +  ==========================================
> +  2 - ARM idle states
> +  ==========================================
>
>    According to the Server Base System Architecture document (SBSA, [3]), the
>    power states an ARM CPU can be put into are identified by the following list:
> @@ -43,8 +48,23 @@ description: |+
>    The device tree binding definition for ARM idle states is the subject of this
>    document.
>
> +  ==========================================
> +  3 - RISC-V idle states
> +  ==========================================
> +
> +  On RISC-V systems, the HARTs (or CPUs) [6] can be put in platform specific
> +  suspend (or idle) states (ranging from simple WFI, power gating, etc). The
> +  RISC-V SBI v0.3 (or higher) [7] hart state management extension provides a
> +  standard mechanism for OS 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 registers and CSR values for all privilege modes whereas
> +  a non-retentive suspend state will not preserve HART registers and CSR
> +  values.
> +
>    ===========================================
> -  2 - idle-states definitions
> +  4 - idle-states definitions
>    ===========================================
>
>    Idle states are characterized for a specific system through a set of
> @@ -211,10 +231,10 @@ description: |+
>    properties specification that is the subject of the following sections.
>
>    ===========================================
> -  3 - idle-states node
> +  5 - idle-states node
>    ===========================================
>
> -  ARM processor idle states are defined within the idle-states node, which is
> +  The processor idle states are defined within the idle-states node, which is
>    a direct child of the cpus node [1] and provides a container where the
>    processor idle states, defined as device tree nodes, are listed.
>
> @@ -223,7 +243,7 @@ description: |+
>    just supports idle_standby, an idle-states node is not required.
>
>    ===========================================
> -  4 - References
> +  6 - References
>    ===========================================
>
>    [1] ARM Linux Kernel documentation - CPUs bindings
> @@ -238,9 +258,15 @@ description: |+
>    [4] ARM Architecture Reference Manuals
>        http://infocenter.arm.com/help/index.jsp
>
> -  [6] ARM Linux Kernel documentation - Booting AArch64 Linux
> +  [5] ARM Linux Kernel documentation - Booting AArch64 Linux
>        Documentation/arm64/booting.rst
>
> +  [6] RISC-V Linux Kernel documentation - CPUs bindings
> +      Documentation/devicetree/bindings/riscv/cpus.yaml
> +
> +  [7] RISC-V Supervisor Binary Interface (SBI)
> +      http://github.com/riscv/riscv-sbi-doc/riscv-sbi.adoc
> +
>  properties:
>    $nodename:
>      const: idle-states
> @@ -253,7 +279,7 @@ properties:
>        On ARM 32-bit systems this property is optional
>
>        This assumes that the "enable-method" property is set to "psci" in the cpu
> -      node[6] that is responsible for setting up CPU idle management in the OS
> +      node[5] that is responsible for setting up CPU idle management in the OS
>        implementation.
>      const: psci
>
> @@ -265,8 +291,8 @@ patternProperties:
>        as follows.
>
>        The idle state entered by executing the wfi instruction (idle_standby
> -      SBSA,[3][4]) is considered standard on all ARM platforms and therefore
> -      must not be listed.
> +      SBSA,[3][4]) is considered standard on all ARM and RISC-V platforms and
> +      therefore must not be listed.
>
>        In addition to the properties listed above, a state node may require
>        additional properties specific to the entry-method defined in the
> @@ -275,7 +301,27 @@ patternProperties:
>
>      properties:
>        compatible:
> -        const: arm,idle-state
> +        enum:
> +          - arm,idle-state
> +          - riscv,idle-state
> +
> +      arm,psci-suspend-param:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description: |
> +          power_state parameter to pass to the ARM PSCI suspend call.
> +
> +          Device tree nodes that require usage of PSCI CPU_SUSPEND function
> +          (i.e. idle states node with entry-method property is set to "psci")
> +          must specify this property.
> +
> +      riscv,sbi-suspend-param:
> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description: |
> +          suspend_type parameter to pass to the RISC-V SBI HSM suspend call.
> +
> +          This property is required in idle state nodes of device tree meant
> +          for RISC-V systems. For more details on the suspend_type parameter
> +          refer the SBI specifiation v0.3 (or higher) [7].
>
>        local-timer-stop:
>          description:
> @@ -317,6 +363,8 @@ patternProperties:
>          description:
>            A string used as a descriptive name for the idle state.
>
> +    additionalProperties: false
> +
>      required:
>        - compatible
>        - entry-latency-us
> @@ -658,4 +706,150 @@ examples:
>          };
>      };
>
> +  - |
> +    // Example 3 (RISC-V 64-bit, 4-cpu systems, two clusters):
> +
> +    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;
> +            };
> +        };
> +
> +        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>;
> +            };
> +        };
> +    };
> +
>  ...
> diff --git a/Documentation/devicetree/bindings/riscv/cpus.yaml b/Documentation/devicetree/bindings/riscv/cpus.yaml
> index aa5fb64d57eb..f62f646bc695 100644
> --- a/Documentation/devicetree/bindings/riscv/cpus.yaml
> +++ b/Documentation/devicetree/bindings/riscv/cpus.yaml
> @@ -99,6 +99,12 @@ properties:
>        - compatible
>        - interrupt-controller
>
> +  cpu-idle-states:
> +    $ref: '/schemas/types.yaml#/definitions/phandle-array'
> +    description: |
> +      List of phandles to idle state nodes supported
> +      by this hart (see ./idle-states.yaml).
> +
>  required:
>    - riscv,isa
>    - interrupt-controller
> --
> 2.25.1
>
>
> --
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> kvm-riscv@xxxxxxxxxxxxxxxxxxx
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-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/