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Subject[PATCH 02/11] dt-bindings: Add an enable method to RISC-V
From: Palmer Dabbelt <>

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. Future systems may have an explicit mechanism for putting a CPU
to sleep, so we're standardizing the device tree entry for when that

We're not defining a spin-table based interface to the firmware, as the
plan is to handle this entirely within the kernel instead.

Signed-off-by: Palmer Dabbelt <>
Signed-off-by: Christoph Hellwig <>
Documentation/devicetree/bindings/riscv/cpus.txt | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/Documentation/devicetree/bindings/riscv/cpus.txt b/Documentation/devicetree/bindings/riscv/cpus.txt
index b0b038d6c406..6aa9cd075a5b 100644
--- a/Documentation/devicetree/bindings/riscv/cpus.txt
+++ b/Documentation/devicetree/bindings/riscv/cpus.txt
@@ -82,6 +82,15 @@ 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: optional
+ Value type: <stringlist>
+ Definition: When absent, default is either "always-disabled"
+ "always-enabled", depending on the current state
+ of the CPU.
+ Must be one of:
+ * "always-disabled": This CPU cannot be enabled.
+ * "always-enabled": This CPU cannot be disabled.

Example: SiFive Freedom U540G Development Kit
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