m68k: math-emu: Fix dependencies of math emulation support

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 M68KCLASSIC (to rule out Coldfire) and FPU (kernel
has some type of floating-point support --- be it hardware or software
emulated, to rule out anything below 68020).

Fixes: 1f7034b9616e6f14 ("m68k: allow ColdFire 547x and 548x CPUs to be built with MMU enabled")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Geert Uytterhoeven <[email protected]>
Reviewed-by: Greg Ungerer <[email protected]>
Link: https://lore.kernel.org/r/18c34695b7c95107f60ccca82a4ff252f3edf477.1652446117.git.geert@linux-m68k.org

diff --git a/arch/m68k/Kconfig.cpu b/arch/m68k/Kconfig.cpu
index 16ea9a67723c09dcb820d933c10a146bb0d1631a..3d5da25c73b5af8aa70f5dbe745557bd6298b49b 100644 (file)
--- 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 M68KCLASSIC && FPU
        help
          At some point in the future, this will cause floating-point math
          instructions to be emulated by the kernel on machines that lack a