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

stable inclusion
from stable-v5.10.121
commit a67a1661cf8a79797f85043d73ebd4df16ebca06
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5L6CQ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=a67a1661cf8a79797f85043d73ebd4df16ebca06

--------------------------------

[ Upstream commit ed6bc6bf ]

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: 1f7034b9 ("m68k: allow ColdFire 547x and 548x CPUs to be built with MMU enabled")
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: NGreg Ungerer <gerg@linux-m68k.org>
Link: https://lore.kernel.org/r/18c34695b7c95107f60ccca82a4ff252f3edf477.1652446117.git.geert@linux-m68k.orgSigned-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>

arch/m68k/Kconfig.cpu

@@ -312,7 +312,7 @@ 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