Re: [PATCH 03/13] ARM: remove riscpc

[Ethan Nelson-Moore]

Hi, everyone,

On Tue, Sep 8, 2026 at 8:29 AM Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
> The main limitation here is the CPU bus that does not allow 16-bit
> wide data transfers and hence requires the kernel to be built with the
> -march=armv3 compiler option that was discontinued in gcc-9.
>
> As gcc-8 is barely supported for compiling the kernel, this one
> will not see another LTS kernel release, so remove it now.

Because I think it's cool that the kernel still supports actual Acorn
hardware, I patched gcc 16.2 to restore ARMv3m support:
https://github.com/EthanNelson-Moore/gcc-arm-retro

This ended up being surprisingly straightforward - only a couple
hundred lines changed - and it would be even fewer lines had I not
reverted a commit that adds a use of ldrh instead of fixing it.

It is able to compile a kernel successfully (once you update the GCC
version check to check for -march=armv3m support instead - I can send
my patch). I haven't tested it, but I am fairly confident that it
would run, because the assembler will reject code the compiler
generates with unsupported instructions - this is how I found the
commit I needed to revert.

I am working on a clocksource driver, which uses both timers (to
hopefully fix the awful time drift), and removes the dependency on
LEGACY_TIMER_TICK.

I also have patches for several cleanups to Risc PC-related code.

I am aware that this has no actual use case, but it was fun. No LLM
was used for any part of the work.

Ethan