Re: [RFT PATCH v1 2/4] dt-binding: cpu-topology: Move cpu-map to a common binding.

Rob Herring
2018-12-12T02:21:17Z

On Mon, Dec 03, 2018 at 09:23:42AM -0800, Atish Patra wrote:
> On 12/3/18 8:55 AM, Sudeep Holla wrote:
> > On Thu, Nov 29, 2018 at 03:28:18PM -0800, Atish Patra wrote:
> > > cpu-map binding can be used to described cpu topology for both
> > > RISC-V & ARM. It makes more sense to move the binding to document
> > > to a common place.
> > >
> > > The relevant discussion can be found here.
> > > https://lkml.org/lkml/2018/11/6/19
> > >
> >
> > Looks good to me apart from a minor query below in the example.
> >
> > Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>
> >
> > > Signed-off-by: Atish Patra <atish.patra@wdc.com>
> > > ---
> > > .../{arm/topology.txt => cpu/cpu-topology.txt} | 81 ++++++++++++++++++----
> > > 1 file changed, 67 insertions(+), 14 deletions(-)
> > > rename Documentation/devicetree/bindings/{arm/topology.txt => cpu/cpu-topology.txt} (86%)
> > >
> > > diff --git a/Documentation/devicetree/bindings/arm/topology.txt b/Documentation/devicetree/bindings/cpu/cpu-topology.txt
> > > similarity index 86%
> > > rename from Documentation/devicetree/bindings/arm/topology.txt
> > > rename to Documentation/devicetree/bindings/cpu/cpu-topology.txt
> > > index 66848355..1de6fbce 100644
> > > --- a/Documentation/devicetree/bindings/arm/topology.txt
> > > +++ b/Documentation/devicetree/bindings/cpu/cpu-topology.txt
> >
> > [...]
> >
> > > +Example 3: HiFive Unleashed (RISC-V 64 bit, 4 core system)
> > > +
> > > +cpus {
> > > + #address-cells = <2>;
> > > + #size-cells = <2>;
> > > + compatible = "sifive,fu540g", "sifive,fu500";
> > > + model = "sifive,hifive-unleashed-a00";
> > > +
> > > + ...
> > > +
> > > + cpu-map {
> > > + cluster0 {
> > > + core0 {
> > > + cpu = <&L12>;
> > > + };
> > > + core1 {
> > > + cpu = <&L15>;
> > > + };
> > > + core2 {
> > > + cpu0 = <&L18>;
> > > + };
> > > + core3 {
> > > + cpu0 = <&L21>;
> > > + };
> > > + };
> > > + };
> > > +
> > > + L12: cpu@1 {
> > > + device_type = "cpu";
> > > + compatible = "sifive,rocket0", "riscv";
> > > + reg = <0x1>;
> > > + }
> > > +
> > > + L15: cpu@2 {
> > > + device_type = "cpu";
> > > + compatible = "sifive,rocket0", "riscv";
> > > + reg = <0x2>;
> > > + }
> > > + L18: cpu@3 {
> > > + device_type = "cpu";
> > > + compatible = "sifive,rocket0", "riscv";
> > > + reg = <0x3>;
> > > + }
> > > + L21: cpu@4 {
> > > + device_type = "cpu";
> > > + compatible = "sifive,rocket0", "riscv";
> > > + reg = <0x4>;
> > > + }
> > > +};
> >
> > The labels for the CPUs drew my attention. Is it intentionally random
> > (or even specific) or just chosen to show anything can be used as labels ?
>
> SiFive generates the device tree from RTL directly. So I am not sure if they
> assign random numbers or a particular algorithm chooses the label. I tried
> to put the exact ones that is available publicly.
>
> https://github.com/riscv/riscv-device-tree-doc/blob/master/examples/sifive-hifive_unleashed-microsemi.dts

Oh, that's really terrible. I wouldn't care as this was just source
level stuff, but labels are part of the ABI with overlays.

Rob