arch/m68k/Kconfig.cpu v5.13-rc1

Processor Type

None

CPU family support

The Freescale (was Motorola) M68K family of processors implements
the full 68000 processor instruction set.
The Freescale ColdFire family of processors is a modern derivative
of the 68000 processor family. They are mainly targeted at embedded
applications, and are all System-On-Chip (SOC) devices, as opposed
to stand alone CPUs. They implement a subset of the original 68000
processor instruction set.
If you anticipate running this kernel on a computer with a classic
MC68xxx processor, select M68KCLASSIC.
If you anticipate running this kernel on a computer with a ColdFire
processor, select COLDFIRE.

M68000

The Freescale (was Motorola) 68000 CPU is the first generation of
the well known M68K family of processors. The CPU core as well as
being available as a stand alone CPU was also used in many
System-On-Chip devices (eg 68328, 68302, etc). It does not contain
a paging MMU.

MCPU32

The Freescale (was then Motorola) CPU32 is a CPU core that is
based on the 68020 processor. For the most part it is used in
System-On-Chip parts, and does not contain a paging MMU.

M68020

68020 support

If you anticipate running this kernel on a computer with a MC68020
processor, say Y. Otherwise, say N. Note that the 68020 requires a
68851 MMU (Memory Management Unit) to run Linux/m68k, except on the
Sun 3, which provides its own version.

M68030

68030 support

If you anticipate running this kernel on a computer with a MC68030
processor, say Y. Otherwise, say N. Note that a MC68EC030 will not
work, as it does not include an MMU (Memory Management Unit).

M68040

68040 support

If you anticipate running this kernel on a computer with a MC68LC040
or MC68040 processor, say Y. Otherwise, say N. Note that an
MC68EC040 will not work, as it does not include an MMU (Memory
Management Unit).

M68060

68060 support

If you anticipate running this kernel on a computer with a MC68060
processor, say Y. Otherwise, say N.

M68328

Motorola 68328 processor support.

M68EZ328

Motorola 68EX328 processor support.

M68VZ328

Motorola 68VZ328 processor support.

M68VZ328

ColdFire SoC type

Select the type of ColdFire System-on-Chip (SoC) that you want
to build for.

M5206

MCF5206

Motorola ColdFire 5206 processor support.

M5206e

MCF5206e

Motorola ColdFire 5206e processor support.

M520x

MCF520x

Freescale Coldfire 5207/5208 processor support.

M523x

MCF523x

Freescale Coldfire 5230/1/2/4/5 processor support

M5249

MCF5249

Motorola ColdFire 5249 processor support.

M525x

MCF525x

Freescale (Motorola) Coldfire 5251/5253 processor support.

M5271

MCF5271

Freescale (Motorola) ColdFire 5270/5271 processor support.

M5272

MCF5272

Motorola ColdFire 5272 processor support.

M5275

MCF5275

Freescale (Motorola) ColdFire 5274/5275 processor support.

M528x

MCF528x

Motorola ColdFire 5280/5282 processor support.

M5307

MCF5307

Motorola ColdFire 5307 processor support.

M532x

MCF532x

Freescale (Motorola) ColdFire 532x processor support.

M537x

MCF537x

Freescale ColdFire 537x processor support.

M5407

MCF5407

Motorola ColdFire 5407 processor support.

M547x

MCF547x

Freescale ColdFire 5470/5471/5472/5473/5474/5475 processor support.

M548x

MCF548x

Freescale ColdFire 5480/5481/5482/5483/5484/5485 processor support.

M5441x

MCF5441x

Freescale Coldfire 54410/54415/54416/54417/54418 processor support.

Processor Specific Options

M68KFPU_EMU

Math emulation support

At some point in the future, this will cause floating-point math
instructions to be emulated by the kernel on machines that lack a
floating-point math coprocessor.  Thrill-seekers and chronically
sleep-deprived psychotic hacker types can say Y now, everyone else
should probably wait a while.

M68KFPU_EMU_EXTRAPREC

Math emulation extra precision

The fpu uses normally a few bit more during calculations for
correct rounding, the emulator can (often) do the same but this
extra calculation can cost quite some time, so you can disable
it here. The emulator will then "only" calculate with a 64 bit
mantissa and round slightly incorrect, what is more than enough
for normal usage.

M68KFPU_EMU_ONLY

Math emulation only kernel

This option prevents any floating-point instructions from being
compiled into the kernel, thereby the kernel doesn't save any
floating point context anymore during task switches, so this
kernel will only be usable on machines without a floating-point
math coprocessor. This makes the kernel a bit faster as no tests
needs to be executed whether a floating-point instruction in the
kernel should be executed or not.

ADVANCED

Advanced configuration options

This gives you access to some advanced options for the CPU. The
defaults should be fine for most users, but these options may make
it possible for you to improve performance somewhat if you know what
you are doing.

Note that the answer to this question won't directly affect the
kernel: saying N will just cause the configurator to skip all
the questions about these options.

Most users should say N to this question.

RMW_INSNS

Use read-modify-write instructions

This allows to use certain instructions that work with indivisible
read-modify-write bus cycles. While this is faster than the
workaround of disabling interrupts, it can conflict with DMA
( = direct memory access) on many Amiga systems, and it is also said
to destabilize other machines. It is very likely that this will
cause serious problems on any Amiga or Atari Medusa if set. The only
configuration where it should work are 68030-based Ataris, where it
apparently improves performance. But you've been warned! Unless you
really know what you are doing, say N. Try Y only if you're quite
adventurous.

SINGLE_MEMORY_CHUNK

Use one physical chunk of memory only

Ignore all but the first contiguous chunk of physical memory for VM
purposes.  This will save a few bytes kernel size and may speed up
some operations.
When this option os set to N, you may want to lower "Maximum zone
order" to save memory that could be wasted for unused memory map.
Say N if not sure.

FORCE_MAX_ZONEORDER

Maximum zone order

The kernel memory allocator divides physically contiguous memory
blocks into "zones", where each zone is a power of two number of
pages.  This option selects the largest power of two that the kernel
keeps in the memory allocator.  If you need to allocate very large
blocks of physically contiguous memory, then you may need to
increase this value.

For systems that have holes in their physical address space this
value also defines the minimal size of the hole that allows
freeing unused memory map.

This config option is actually maximum order plus one. For example,
a value of 11 means that the largest free memory block is 2^10 pages.

060_WRITETHROUGH

Use write-through caching for 68060 supervisor accesses

The 68060 generally uses copyback caching of recently accessed data.
Copyback caching means that memory writes will be held in an on-chip
cache and only written back to memory some time later.  Saying Y
here will force supervisor (kernel) accesses to use writethrough
caching.  Writethrough caching means that data is written to memory
straight away, so that cache and memory data always agree.
Writethrough caching is less efficient, but is needed for some
drivers on 68060 based systems where the 68060 bus snooping signal
is hardwired on.  The 53c710 SCSI driver is known to suffer from
this problem.

CLOCK_FREQ

Set the core clock frequency

Define the CPU clock frequency in use. This is the core clock
frequency, it may or may not be the same as the external clock
crystal fitted to your board. Some processors have an internal
PLL and can have their frequency programmed at run time, others
use internal dividers. In general the kernel won't setup a PLL
if it is fitted (there are some exceptions). This value will be
specific to the exact CPU that you are using.

OLDMASK

Old mask 5307 (1H55J) silicon

Build support for the older revision ColdFire 5307 silicon.
Specifically this is the 1H55J mask revision.

CACHE_I

Instruction

Use all of the ColdFire CPU cache memory as an instruction cache.

CACHE_D

Data

Use all of the ColdFire CPU cache memory as a data cache.

CACHE_BOTH

Both

Split the ColdFire CPU cache, and use half as an instruction cache
and half as a data cache.

CACHE_WRITETHRU

Write-through

The ColdFire CPU cache is set into Write-through mode.

CACHE_COPYBACK

Copy-back

The ColdFire CPU cache is set into Copy-back mode.