Re: [PATCH] m68k: math-emu: Fix dependencies of math emulation support

[Greg Ungerer]

Hi Geert,

On 11/5/22 22:54, Geert Uytterhoeven wrote:
> On Wed, May 11, 2022 at 11:48 AM Geert Uytterhoeven
> <geert@xxxxxxxxxxxxxx> wrote:
> > If CONFIG_M54xx=y, CONFIG_MMU=y, and CONFIG_M68KFPU_EMU=y:
> >
> >      {standard input}:272: Error: invalid instruction for this architecture; needs 68000 or higher (68000 [68ec000, 68hc000, 68hc001, 68008, 68302, 68306, 68307, 68322, 68356], 68010, 68020 [68k, 68ec020], 68030 [68ec030], 68040 [68ec040], 68060 [68ec060], cpu32 [68330, 68331, 68332, 68333, 68334, 68336, 68340, 68341, 68349, 68360], fidoa [fido]) -- statement `sub.b %d1,%d3' ignored
> >      {standard input}:609: Error: invalid instruction for this architecture; needs 68020 or higher (68020 [68k, 68ec020], 68030 [68ec030], 68040 [68ec040], 68060 [68ec060]) -- statement `bfextu 4(%a1){%d0,#8},%d0' ignored
> >      {standard input}:752: Error: operands mismatch -- statement `mulu.l 4(%a0),%d3:%d0' ignored
> >      {standard input}:1155: Error: operands mismatch -- statement `divu.l %d0,%d3:%d7' ignored
> >
> > The math emulation support code is intended for 68020 and higher, and
> > uses several instructions or instruction modes not available on coldfire
> > or 68000.
> >
> > Originally, the dependency of M68KFPU_EMU on MMU was fine, as MMU
> > support was only available on 68020 or higher.  But this assumption
> > was broken by the introduction of MMU support for M547x and M548x.
> >
> > Drop the dependency on MMU, as the code should work fine on 68020 and up
> > without MMU (which are not yet supported by Linux, though).
> > Add dependencies on M68K_CLASSIC (to rule out Coldfire) and FPU (to rule
> > out 68xxx below 68020).
> >
> > Fixes: 1f7034b9616e6f14 ("m68k: allow ColdFire 547x and 548x CPUs to be built with MMU enabled")
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
> > ---
> > To be queued in the m68k for-v5.19 branch.
> >
> >   arch/m68k/Kconfig.cpu | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/m68k/Kconfig.cpu b/arch/m68k/Kconfig.cpu
> > index 16ea9a67723c09dc..9abddbbee819f1d3 100644
> > --- a/arch/m68k/Kconfig.cpu
> > +++ b/arch/m68k/Kconfig.cpu
> > @@ -327,7 +327,7 @@ comment "Processor Specific Options"
> >
> >   config M68KFPU_EMU
> >          bool "Math emulation support"
> > -       depends on MMU
> > +       depends on M68K_CLASSIC && FPU
>                        ^^^^^^^^^^^^
> Whoops, that's a silly typo...

Are you going to resend, or are you thinking of changing the way this is done?

I had thought that CONFIG_FPU enabled meant you had some type of
floating point support in the kernel - be it hardware or software emulated.
So I don't have a problem with this "as is".

Regards
Greg