[PATCH v11 7/8] dt-bindings: Add common bindings for ARM and RISC-V idle states

Anup Patel
2022-02-10T05:51:36Z

From: Anup Patel <anup.patel@wdc.com>

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@wdc.com>
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Guo Ren <guoren@kernel.org>
---
.../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@arm.com>
+ - Anup Patel <anup@brainfault.org>

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