linux-kernel - [PATCH] dt-bindings: Add an enable method to RISC-V

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Date:   Mon, 20 Nov 2017 11:50:22 -0800
From:   Palmer Dabbelt <palmer@...ive.com>
To:     mark.rutland@....com, robh+dt@...nel.org,
        devicetree@...r.kernel.org
Cc:     patches@...ups.riscv.org, linux-kernel@...r.kernel.org,
        Palmer Dabbelt <palmer@...ive.com>
Subject: [PATCH] dt-bindings: Add an enable method to RISC-V

RISC-V doesn't currently specify a mechanism for enabling or disabling
CPUs.  Instead, we assume that all CPUs are enabled on boot, and if
someone wants to save power we instead put a CPU to sleep via a WFI
loop.

This patch adds "enable-method" to the RISC-V CPU binding, which
currently only has the value "none".  This allows us to change the
enable method in the future.

CC: Mark Rutland <mark.rutland@....com>
Signed-off-by: Palmer Dabbelt <palmer@...ive.com>
---
 Documentation/devicetree/bindings/riscv/cpus.txt | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Documentation/devicetree/bindings/riscv/cpus.txt b/Documentation/devicetree/bindings/riscv/cpus.txt
index adf7b7af5dc3..dd9e1ae197e2 100644
--- a/Documentation/devicetree/bindings/riscv/cpus.txt
+++ b/Documentation/devicetree/bindings/riscv/cpus.txt
@@ -82,6 +82,11 @@ described below.
                 Value type: <string>
                 Definition: Contains the RISC-V ISA string of this hart.  These
                             ISA strings are defined by the RISC-V ISA manual.
+        - cpu-enable-method:
+		Usage: required
+		Value type: <stringlist>
+		Definition: Must be one of
+			"none": This CPU's state cannot be changed.
 
 Example: SiFive Freedom U540G Development Kit
 ---------------------------------------------
@@ -105,6 +110,7 @@ Linux is allowed to run on.
                         reg = <0>;
                         riscv,isa = "rv64imac";
                         status = "disabled";
+                        enable-method = "none";
                         L10: interrupt-controller {
                                 #interrupt-cells = <1>;
                                 compatible = "riscv,cpu-intc";
@@ -130,6 +136,7 @@ Linux is allowed to run on.
                         reg = <1>;
                         riscv,isa = "rv64imafdc";
                         status = "okay";
+                        enable-method = "none";
                         tlb-split;
                         L13: interrupt-controller {
                                 #interrupt-cells = <1>;
-- 
2.13.6