Re: [PATCH 2/3] m68k: Add support for M68040 CPU

[Kuan-Wei Chiu <visitorckw@gmail.com>]

Hi Daniel,

On Sun, Dec 21, 2025 at 01:53:40PM +0900, Daniel Palmer wrote:
> Hi Kuan-Wei
> 
> On Fri, 19 Dec 2025 at 04:06, Kuan-Wei Chiu <visitorckw@gmail.com> wrote:
> >
> > Add support for the Motorola 68040 architecture. Currently, m68k
> > support in U-Boot is primarily focused on ColdFire (MCF5xxx) variants.
> > Introduce the necessary infrastructure to support the classic M680x0
> > series, specifically targeting the M68040 as emulated by QEMU.
> 
> For all of this: It really needs to be split into the bits for all
> classic 68K and then the supplemental bits for 040 (basically the
> cache stuff that you only have stubs for).
> That way if your parts get merged I can rework my support for 000, 030
> etc on top of that.

Yeah, proper split is definitely needed for the long term.

Here is my plan for v2 to address this. Could you let me know if this
structure matches what you have in mind?

1. Create a common directory for Classic m68k (non-ColdFire):
   Possible path: arch/m68k/cpu/classic/

   I plan to move the following generic parts there:
   - start.S: The entry point, basic stack setup, and exception vector
     definitions (likely shared across 000-060).
   - bootinfo.h: Since this is standard for m68k Linux.

2. Keep 040-specific code in arch/m68k/cpu/classic/m68040/:
   - cpu.c: Containing 040-specific cache handling (or stubs for
     now) and specific initialization.

3. Refactor arch/m68k/lib/Makefile:
   Instead of using ifndef CONFIG_M68040 to exclude ColdFire files, I
   should probably restructure it to clearly distinguish between
   "ColdFire common" and "Classic m68k common" libraries.

Does this separation align with your requirements for layering 000/030
support on top of it later?

Regards,
Kuan-Wei