RISC-V CPU Idle Support

This series adds RISC-V CPU Idle support using SBI HSM suspend function.
The RISC-V SBI CPU idle driver added by this series is highly inspired
from the ARM PSCI CPU idle driver.

Special thanks Sandeep Tripathy for providing early feeback on SBI HSM
support in all above projects (RISC-V SBI specification, OpenSBI, and
Linux RISC-V).

* palmer/riscv-idle:
  RISC-V: Enable RISC-V SBI CPU Idle driver for QEMU virt machine
  dt-bindings: Add common bindings for ARM and RISC-V idle states
  cpuidle: Add RISC-V SBI CPU idle driver
  cpuidle: Factor-out power domain related code from PSCI domain driver
  RISC-V: Add SBI HSM suspend related defines
  RISC-V: Add arch functions for non-retentive suspend entry/exit
  RISC-V: Rename relocate() and make it global
  RISC-V: Enable CPU_IDLE drivers

4 files changed, 219 insertions, 19 deletions

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
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