On Thu, Aug 2, 2018 at 5:50 AM Christoph Hellwig <hch@xxxxxx> wrote: > > From: Palmer Dabbelt <palmer@xxxxxxxxxx> > > 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 > happens. > > 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 <palmer@xxxxxxxxxx> > Signed-off-by: Christoph Hellwig <hch@xxxxxx> > --- > 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: Something wrong with "enable-method" as defined in the DT spec[1]? > + 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. To follow the spec, 'enable-method' should simply not be present in the always-enabled case. I think the always disabled case should be handled with: status = "disabled"; enable-method = "none"; With "none" needing to be added to the spec. [1] https://github.com/devicetree-org/devicetree-specification/blob/master/source/devicenodes.rst#general-properties-of-cpuscpu-nodes -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
