On Sat, May 27, 2017 at 2:57 AM, Palmer Dabbelt <pal...@dabbelt.com> wrote:
> On Tue, 23 May 2017 04:30:50 PDT (-0700), Arnd Bergmann wrote:
>> On Tue, May 23, 2017 at 2:41 AM, Palmer Dabbelt <pal...@dabbelt.com> wrote:
>>> RISC-V has both 32-bit and 64-bit base ISAs, but they are very similar.
>>> Like some other platforms, we'd like to share one arch directory between
>>> the two of them.
>>
>> I think we mainly do the others for backwards-compatibility with ancient
>> build scripts, and we don't need that here. Instead, you could add one more
>> line to the 'SUBARCH:=' statement that interprets the uname output.
>
> I don't think that does the same thing. The desired effect of this diff is:
>
> * "uname -m" when running on a RISC-V machine returns either riscv32 or
> riscv64, as that's what tools like autoconf expect when trying to find
> tuples.
>
> * I can cross compile for riscv32 and riscv64. That's currently controlled
> by
> a Kconfig setting, but ARCH=riscv32 vs ARCH=riscv64 controlls what
> defconfig
> sets.
>
> * I can natively compile for riscv32 and riscv64. That uses the same Kconfig
> setting, and the same ARCH=riscv32 vs ARCH=riscv64 switch for defconfig.
Right, but my point is that a new architecture should not rely on 'ARCH='
to pick the defconfig, we only do that on a couple of architectures for
backwards compatibility with old scripts.
> Neither of the two Kconfig issues is a big deal, but we de need "uname -m" to
> return "riscv64" or "riscv32" not "riscv". I think the only way to do that is
> to set SRCARCH, but I'd be happy to change it if there's a better way. I
> think
> if I just do this
>
> diff --git a/Makefile b/Makefile
> index 0606f28..4adc609 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -232,7 +232,8 @@ SUBARCH := $(shell uname -m | sed -e s/i.86/x86/ -e
> s/x86_64/x86/ \
> -e s/arm.*/arm/ -e s/sa110/arm/ \
> -e s/s390x/s390/ -e s/parisc64/parisc/ \
> -e s/ppc.*/powerpc/ -e s/mips.*/mips/ \
> - -e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ )
> + -e s/sh[234].*/sh/ -e s/aarch64.*/arm64/ \
> + -e s/riscv.*/riscv/ )
>
> # Cross compiling and selecting different set of gcc/bin-utils
> # ---------------------------------------------------------------------------
> @@ -269,14 +270,6 @@ ifeq ($(ARCH),x86_64)
> SRCARCH := x86
> endif
>
> -# Additional ARCH settings for RISC-V
> -ifeq ($(ARCH),riscv32)
> - SRCARCH := riscv
> -endif
> -ifeq ($(ARCH),riscv64)
> - SRCARCH := riscv
> -endif
> -
> # Additional ARCH settings for sparc
> ifeq ($(ARCH),sparc32)
> SRCARCH := sparc
>
> then I'll end up with "uname -m" as "riscv" -- I haven't tried it, but that's
> why we ended up with this diff in the first place.
Do you mean the "uname -m" output comes from "${SRCARCH}" at
the time of the kernel build? That would be easy enough to change
by simply hardcoding it depending on CONFIG_64BIT.
Arnd
