Hi Geoff, On Fri, Aug 15, 2014 at 08:48:50PM +0100, Geoff Levand wrote: > Add a new device tree binding cpu-return-addr. This binding is required for > all ARM v8 CPUs that have an "enable-method" property value of "spin-table". The > value is a 64 bit read-only physical address that secondary CPU execution will > transfer to upon CPU shutdown. As we already have implementations of spin-table which won't necessarily be able to implement cpu-return-addr I do not think this can be required for all spin-table implementations. Given that it's probably not worth updating the topology documentation. > Signed-off-by: Geoff Levand <geoff@xxxxxxxxxxxxx> > --- > Hi All, > > We currently have no way for arm64 spin-table CPUs to re-enter the spin > table code, and some way to do so is needed to implement a hot-plug > cpu_die() for these CPUs. > > I just wanted to get this binding patch out for review now. I have other > patches that implement the spin-table hot-plug in my kexec repo [1]. > > Please consider. > > -Geoff > > [1] https://git.linaro.org/people/geoff.levand/linux-kexec.git > > Documentation/devicetree/bindings/arm/cpus.txt | 26 ++++++++++++++++++++++ > Documentation/devicetree/bindings/arm/topology.txt | 16 +++++++++++++ > 2 files changed, 42 insertions(+) > > diff --git a/Documentation/devicetree/bindings/arm/cpus.txt b/Documentation/devicetree/bindings/arm/cpus.txt > index 1fe72a0..24b98a9 100644 > --- a/Documentation/devicetree/bindings/arm/cpus.txt > +++ b/Documentation/devicetree/bindings/arm/cpus.txt > @@ -201,6 +201,16 @@ nodes to be present and contain the properties described below. > property identifying a 64-bit zero-initialised > memory location. > > + - cpu-return-addr > + Usage: required for all ARM v8 CPUs that have an "enable-method" > + property value of "spin-table". > + Value type: <prop-encoded-array> > + Definition: > + # On ARM v8 64-bit systems must be a two cell property. > + The value is a 64 bit read-only physical address that > + secondary CPU execution will transfer to upon CPU > + shutdown. I'm not sure what's meant by read-only here. We're never likely to read anything from that physical address, just branch the CPU there. Cheers, Mark. -- 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
