On Fri, Jan 4, 2019 at 4:46 PM Palmer Dabbelt <[email protected]> wrote: > > On Thu, 20 Dec 2018 13:01:41 PST (-0800), [email protected] wrote: > > On Fri, Dec 14, 2018 at 09:21:50PM -0800, Paul Walmsley wrote: > >> Add compatible strings for the SiFive E51 family of CPU cores to the > >> RISC-V CPU compatible string documentation. The E51 CPU core is > >> described in: > >> > >> https://static.dev.sifive.com/FU540-C000-v1.0.pdf > >> > >> Cc: Rob Herring <[email protected]> > >> Cc: Mark Rutland <[email protected]> > >> Cc: Palmer Dabbelt <[email protected]> > >> Cc: Albert Ou <[email protected]> > >> Cc: [email protected] > >> Cc: [email protected] > >> Cc: [email protected] > >> Signed-off-by: Paul Walmsley <[email protected]> > >> Signed-off-by: Paul Walmsley <[email protected]> > >> --- > >> Documentation/devicetree/bindings/riscv/cpus.txt | 5 +++-- > >> 1 file changed, 3 insertions(+), 2 deletions(-) > >> > >> diff --git a/Documentation/devicetree/bindings/riscv/cpus.txt > >> b/Documentation/devicetree/bindings/riscv/cpus.txt > >> index adf7b7af5dc3..fb9d4f86f41f 100644 > >> --- a/Documentation/devicetree/bindings/riscv/cpus.txt > >> +++ b/Documentation/devicetree/bindings/riscv/cpus.txt > >> @@ -68,8 +68,9 @@ described below. > >> - compatible: > >> Usage: required > >> Value type: <stringlist> > >> - Definition: must contain "riscv", may contain one of > >> - "sifive,rocket0" > >> + Definition: must contain "riscv", may contain one or > >> + more of "sifive,rocket0", "sifive,e51", > >> + "sifive,e5" > > > > I can't really tell what are valid combinations from this. It reads that > > I could list every string here and that would be valid. It is basically > > 'riscv' plus any other combinations of strings. > > I think that's actually the correct interpretation: if it's a RISC-V CPU then > it must have "riscv" listed in compatible, but it can also be anything else.
But is '"sifive,rocket0", "sifive,e51", "sifive,e5", "riscv"' valid? What about '"sifive,rocket0", "sifive,e5", "riscv"'? If they are, is there really any value in specifying all of them or different variations? I'd suggest keeping things simple because writing a json-schema gets messy when there's arbitrary combinations of compatible values. > There's some concrete examples here (a "sifive,e51" is a type of "riscv"), but > I don't think it's realistic to count on us being able to enumerate all RISC-V > implementations here. I think you'll find that "riscv" will become pointless as it is not specific enough to mean anything. It would be like having "arm" as a compatible on Arm based systems. OTOH, you only really need to enumerate what you can't discover. For example, how are optional features (SIMD inst a common example) discovered? On Arm, we generally just have the CPU model in the compatible, but it's generally not even used because that, cpu revision, instruction set features, etc. are all discoverable. Rob
