On Sat, Jun 3, 2023, at 11:05, Zhangjin Wu wrote:
> Both riscv64 and riscv32 have:
>
> * the same ARCH value, it is riscv
> * the same arch/riscv source code tree
>
> The only differences are:
>
> * riscv64 uses defconfig, riscv32 uses rv32_defconfig
> * riscv64 uses qemu-system-riscv64, riscv32 uses qemu-system-riscv32
> * riscv32 has different compiler options (-march= and -mabi=)
>
> So, riscv32 can share most of the settings with riscv64, there is no
> need to add it as a whole new architecture but just need a flag to
> record and reflect the difference.
>
> The 32bit mips and loongarch may be able to use the same method, so,
> let's use a meaningful flag: CONFIG_32BIT. If required in the future,
> this flag can also be automatically loaded from
> include/config/auto.conf.
If we use a CONFIG_* symbol, I think it should be the other way
round, for consistency with the kernel, which uses CONFIG_64BIT
on all architectures, but only uses CONFIG_32BIT on mips, loongarch
powerpc and riscv.
> # kernel image names by architecture
> IMAGE_i386 = arch/x86/boot/bzImage
> IMAGE_x86_64 = arch/x86/boot/bzImage
> @@ -34,7 +40,7 @@ DEFCONFIG_x86 = defconfig
> DEFCONFIG_arm64 = defconfig
> DEFCONFIG_arm = multi_v7_defconfig
> DEFCONFIG_mips = malta_defconfig
> -DEFCONFIG_riscv = defconfig
> +DEFCONFIG_riscv = $(if $(CONFIG_32BIT),rv32_defconfig,defconfig)
> DEFCONFIG_s390 = defconfig
> DEFCONFIG_loongarch = defconfig
> DEFCONFIG = $(DEFCONFIG_$(ARCH))
This feels slightly odd, as we otherwise have a fixed defconfig
per target, so doing
DEFCONFIG_riscv = defconfig
DEFCONFIG_riscv64 = defconfig
DEFCONFIG_riscv32 = rv32_defconfig
would seem more consistent with how x86 is handled, and would
probably be more easily extensible if we want to also make
this work with other sub-targets like mipseb, armv5 or ppc32
in the future.
Arnd
