xref: /openbmc/linux/arch/arm/mm/Kconfig (revision cd4d09ec)

comment "Processor Type"

# Select CPU types depending on the architecture selected.  This selects
# which CPUs we support in the kernel image, and the compiler instruction
# optimiser behaviour.

# ARM7TDMI
config CPU_ARM7TDMI
	bool
	depends on !MMU
	select CPU_32v4T
	select CPU_ABRT_LV4T
	select CPU_CACHE_V4
	select CPU_PABRT_LEGACY
	help
	  A 32-bit RISC microprocessor based on the ARM7 processor core
	  which has no memory control unit and cache.

	  Say Y if you want support for the ARM7TDMI processor.
	  Otherwise, say N.

# ARM720T
config CPU_ARM720T
	bool
	select CPU_32v4T
	select CPU_ABRT_LV4T
	select CPU_CACHE_V4
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WT if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WT if MMU
	help
	  A 32-bit RISC processor with 8kByte Cache, Write Buffer and
	  MMU built around an ARM7TDMI core.

	  Say Y if you want support for the ARM720T processor.
	  Otherwise, say N.

# ARM740T
config CPU_ARM740T
	bool
	depends on !MMU
	select CPU_32v4T
	select CPU_ABRT_LV4T
	select CPU_CACHE_V4
	select CPU_CP15_MPU
	select CPU_PABRT_LEGACY
	help
	  A 32-bit RISC processor with 8KB cache or 4KB variants,
	  write buffer and MPU(Protection Unit) built around
	  an ARM7TDMI core.

	  Say Y if you want support for the ARM740T processor.
	  Otherwise, say N.

# ARM9TDMI
config CPU_ARM9TDMI
	bool
	depends on !MMU
	select CPU_32v4T
	select CPU_ABRT_NOMMU
	select CPU_CACHE_V4
	select CPU_PABRT_LEGACY
	help
	  A 32-bit RISC microprocessor based on the ARM9 processor core
	  which has no memory control unit and cache.

	  Say Y if you want support for the ARM9TDMI processor.
	  Otherwise, say N.

# ARM920T
config CPU_ARM920T
	bool
	select CPU_32v4T
	select CPU_ABRT_EV4T
	select CPU_CACHE_V4WT
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
	help
	  The ARM920T is licensed to be produced by numerous vendors,
	  and is used in the Cirrus EP93xx and the Samsung S3C2410.

	  Say Y if you want support for the ARM920T processor.
	  Otherwise, say N.

# ARM922T
config CPU_ARM922T
	bool
	select CPU_32v4T
	select CPU_ABRT_EV4T
	select CPU_CACHE_V4WT
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
	help
	  The ARM922T is a version of the ARM920T, but with smaller
	  instruction and data caches. It is used in Altera's
	  Excalibur XA device family and Micrel's KS8695 Centaur.

	  Say Y if you want support for the ARM922T processor.
	  Otherwise, say N.

# ARM925T
config CPU_ARM925T
	bool
	select CPU_32v4T
	select CPU_ABRT_EV4T
	select CPU_CACHE_V4WT
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
 	help
 	  The ARM925T is a mix between the ARM920T and ARM926T, but with
	  different instruction and data caches. It is used in TI's OMAP
 	  device family.

 	  Say Y if you want support for the ARM925T processor.
 	  Otherwise, say N.

# ARM926T
config CPU_ARM926T
	bool
	select CPU_32v5
	select CPU_ABRT_EV5TJ
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
	help
	  This is a variant of the ARM920.  It has slightly different
	  instruction sequences for cache and TLB operations.  Curiously,
	  there is no documentation on it at the ARM corporate website.

	  Say Y if you want support for the ARM926T processor.
	  Otherwise, say N.

# FA526
config CPU_FA526
	bool
	select CPU_32v4
	select CPU_ABRT_EV4
	select CPU_CACHE_FA
	select CPU_CACHE_VIVT
	select CPU_COPY_FA if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_FA if MMU
	help
	  The FA526 is a version of the ARMv4 compatible processor with
	  Branch Target Buffer, Unified TLB and cache line size 16.

	  Say Y if you want support for the FA526 processor.
	  Otherwise, say N.

# ARM940T
config CPU_ARM940T
	bool
	depends on !MMU
	select CPU_32v4T
	select CPU_ABRT_NOMMU
	select CPU_CACHE_VIVT
	select CPU_CP15_MPU
	select CPU_PABRT_LEGACY
	help
	  ARM940T is a member of the ARM9TDMI family of general-
	  purpose microprocessors with MPU and separate 4KB
	  instruction and 4KB data cases, each with a 4-word line
	  length.

	  Say Y if you want support for the ARM940T processor.
	  Otherwise, say N.

# ARM946E-S
config CPU_ARM946E
	bool
	depends on !MMU
	select CPU_32v5
	select CPU_ABRT_NOMMU
	select CPU_CACHE_VIVT
	select CPU_CP15_MPU
	select CPU_PABRT_LEGACY
	help
	  ARM946E-S is a member of the ARM9E-S family of high-
	  performance, 32-bit system-on-chip processor solutions.
	  The TCM and ARMv5TE 32-bit instruction set is supported.

	  Say Y if you want support for the ARM946E-S processor.
	  Otherwise, say N.

# ARM1020 - needs validating
config CPU_ARM1020
	bool
	select CPU_32v5
	select CPU_ABRT_EV4T
	select CPU_CACHE_V4WT
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
	help
	  The ARM1020 is the 32K cached version of the ARM10 processor,
	  with an addition of a floating-point unit.

	  Say Y if you want support for the ARM1020 processor.
	  Otherwise, say N.

# ARM1020E - needs validating
config CPU_ARM1020E
	bool
	depends on n
	select CPU_32v5
	select CPU_ABRT_EV4T
	select CPU_CACHE_V4WT
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU

# ARM1022E
config CPU_ARM1022
	bool
	select CPU_32v5
	select CPU_ABRT_EV4T
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU # can probably do better
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
	help
	  The ARM1022E is an implementation of the ARMv5TE architecture
	  based upon the ARM10 integer core with a 16KiB L1 Harvard cache,
	  embedded trace macrocell, and a floating-point unit.

	  Say Y if you want support for the ARM1022E processor.
	  Otherwise, say N.

# ARM1026EJ-S
config CPU_ARM1026
	bool
	select CPU_32v5
	select CPU_ABRT_EV5T # But need Jazelle, but EV5TJ ignores bit 10
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU # can probably do better
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
	help
	  The ARM1026EJ-S is an implementation of the ARMv5TEJ architecture
	  based upon the ARM10 integer core.

	  Say Y if you want support for the ARM1026EJ-S processor.
	  Otherwise, say N.

# SA110
config CPU_SA110
	bool
	select CPU_32v3 if ARCH_RPC
	select CPU_32v4 if !ARCH_RPC
	select CPU_ABRT_EV4
	select CPU_CACHE_V4WB
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WB if MMU
	help
	  The Intel StrongARM(R) SA-110 is a 32-bit microprocessor and
	  is available at five speeds ranging from 100 MHz to 233 MHz.
	  More information is available at
	  <http://developer.intel.com/design/strong/sa110.htm>.

	  Say Y if you want support for the SA-110 processor.
	  Otherwise, say N.

# SA1100
config CPU_SA1100
	bool
	select CPU_32v4
	select CPU_ABRT_EV4
	select CPU_CACHE_V4WB
	select CPU_CACHE_VIVT
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WB if MMU

# XScale
config CPU_XSCALE
	bool
	select CPU_32v5
	select CPU_ABRT_EV5T
	select CPU_CACHE_VIVT
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU

# XScale Core Version 3
config CPU_XSC3
	bool
	select CPU_32v5
	select CPU_ABRT_EV5T
	select CPU_CACHE_VIVT
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU
	select IO_36

# Marvell PJ1 (Mohawk)
config CPU_MOHAWK
	bool
	select CPU_32v5
	select CPU_ABRT_EV5T
	select CPU_CACHE_VIVT
	select CPU_COPY_V4WB if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_V4WBI if MMU

# Feroceon
config CPU_FEROCEON
	bool
	select CPU_32v5
	select CPU_ABRT_EV5T
	select CPU_CACHE_VIVT
	select CPU_COPY_FEROCEON if MMU
	select CPU_CP15_MMU
	select CPU_PABRT_LEGACY
	select CPU_TLB_FEROCEON if MMU

config CPU_FEROCEON_OLD_ID
	bool "Accept early Feroceon cores with an ARM926 ID"
	depends on CPU_FEROCEON && !CPU_ARM926T
	default y
	help
	  This enables the usage of some old Feroceon cores
	  for which the CPU ID is equal to the ARM926 ID.
	  Relevant for Feroceon-1850 and early Feroceon-2850.

# Marvell PJ4
config CPU_PJ4
	bool
	select ARM_THUMBEE
	select CPU_V7

config CPU_PJ4B
	bool
	select CPU_V7

# ARMv6
config CPU_V6
	bool
	select CPU_32v6
	select CPU_ABRT_EV6
	select CPU_CACHE_V6
	select CPU_CACHE_VIPT
	select CPU_COPY_V6 if MMU
	select CPU_CP15_MMU
	select CPU_HAS_ASID if MMU
	select CPU_PABRT_V6
	select CPU_TLB_V6 if MMU

# ARMv6k
config CPU_V6K
	bool
	select CPU_32v6
	select CPU_32v6K
	select CPU_ABRT_EV6
	select CPU_CACHE_V6
	select CPU_CACHE_VIPT
	select CPU_COPY_V6 if MMU
	select CPU_CP15_MMU
	select CPU_HAS_ASID if MMU
	select CPU_PABRT_V6
	select CPU_TLB_V6 if MMU

# ARMv7
config CPU_V7
	bool
	select CPU_32v6K
	select CPU_32v7
	select CPU_ABRT_EV7
	select CPU_CACHE_V7
	select CPU_CACHE_VIPT
	select CPU_COPY_V6 if MMU
	select CPU_CP15_MMU if MMU
	select CPU_CP15_MPU if !MMU
	select CPU_HAS_ASID if MMU
	select CPU_PABRT_V7
	select CPU_TLB_V7 if MMU

# ARMv7M
config CPU_V7M
	bool
	select CPU_32v7M
	select CPU_ABRT_NOMMU
	select CPU_CACHE_NOP
	select CPU_PABRT_LEGACY
	select CPU_THUMBONLY

config CPU_THUMBONLY
	bool
	# There are no CPUs available with MMU that don't implement an ARM ISA:
	depends on !MMU
	help
	  Select this if your CPU doesn't support the 32 bit ARM instructions.

# Figure out what processor architecture version we should be using.
# This defines the compiler instruction set which depends on the machine type.
config CPU_32v3
	bool
	select CPU_USE_DOMAINS if MMU
	select NEED_KUSER_HELPERS
	select TLS_REG_EMUL if SMP || !MMU

config CPU_32v4
	bool
	select CPU_USE_DOMAINS if MMU
	select NEED_KUSER_HELPERS
	select TLS_REG_EMUL if SMP || !MMU

config CPU_32v4T
	bool
	select CPU_USE_DOMAINS if MMU
	select NEED_KUSER_HELPERS
	select TLS_REG_EMUL if SMP || !MMU

config CPU_32v5
	bool
	select CPU_USE_DOMAINS if MMU
	select NEED_KUSER_HELPERS
	select TLS_REG_EMUL if SMP || !MMU

config CPU_32v6
	bool
	select TLS_REG_EMUL if !CPU_32v6K && !MMU

config CPU_32v6K
	bool

config CPU_32v7
	bool

config CPU_32v7M
	bool

# The abort model
config CPU_ABRT_NOMMU
	bool

config CPU_ABRT_EV4
	bool

config CPU_ABRT_EV4T
	bool

config CPU_ABRT_LV4T
	bool

config CPU_ABRT_EV5T
	bool

config CPU_ABRT_EV5TJ
	bool

config CPU_ABRT_EV6
	bool

config CPU_ABRT_EV7
	bool

config CPU_PABRT_LEGACY
	bool

config CPU_PABRT_V6
	bool

config CPU_PABRT_V7
	bool

# The cache model
config CPU_CACHE_V4
	bool

config CPU_CACHE_V4WT
	bool

config CPU_CACHE_V4WB
	bool

config CPU_CACHE_V6
	bool

config CPU_CACHE_V7
	bool

config CPU_CACHE_NOP
	bool

config CPU_CACHE_VIVT
	bool

config CPU_CACHE_VIPT
	bool

config CPU_CACHE_FA
	bool

if MMU
# The copy-page model
config CPU_COPY_V4WT
	bool

config CPU_COPY_V4WB
	bool

config CPU_COPY_FEROCEON
	bool

config CPU_COPY_FA
	bool

config CPU_COPY_V6
	bool

# This selects the TLB model
config CPU_TLB_V4WT
	bool
	help
	  ARM Architecture Version 4 TLB with writethrough cache.

config CPU_TLB_V4WB
	bool
	help
	  ARM Architecture Version 4 TLB with writeback cache.

config CPU_TLB_V4WBI
	bool
	help
	  ARM Architecture Version 4 TLB with writeback cache and invalidate
	  instruction cache entry.

config CPU_TLB_FEROCEON
	bool
	help
	  Feroceon TLB (v4wbi with non-outer-cachable page table walks).

config CPU_TLB_FA
	bool
	help
	  Faraday ARM FA526 architecture, unified TLB with writeback cache
	  and invalidate instruction cache entry. Branch target buffer is
	  also supported.

config CPU_TLB_V6
	bool

config CPU_TLB_V7
	bool

config VERIFY_PERMISSION_FAULT
	bool
endif

config CPU_HAS_ASID
	bool
	help
	  This indicates whether the CPU has the ASID register; used to
	  tag TLB and possibly cache entries.

config CPU_CP15
	bool
	help
	  Processor has the CP15 register.

config CPU_CP15_MMU
	bool
	select CPU_CP15
	help
	  Processor has the CP15 register, which has MMU related registers.

config CPU_CP15_MPU
	bool
	select CPU_CP15
	help
	  Processor has the CP15 register, which has MPU related registers.

config CPU_USE_DOMAINS
	bool
	help
	  This option enables or disables the use of domain switching
	  via the set_fs() function.

config CPU_V7M_NUM_IRQ
	int "Number of external interrupts connected to the NVIC"
	depends on CPU_V7M
	default 90 if ARCH_STM32
	default 38 if ARCH_EFM32
	default 112 if SOC_VF610
	default 240
	help
	  This option indicates the number of interrupts connected to the NVIC.
	  The value can be larger than the real number of interrupts supported
	  by the system, but must not be lower.
	  The default value is 240, corresponding to the maximum number of
	  interrupts supported by the NVIC on Cortex-M family.

	  If unsure, keep default value.

#
# CPU supports 36-bit I/O
#
config IO_36
	bool

comment "Processor Features"

config ARM_LPAE
	bool "Support for the Large Physical Address Extension"
	depends on MMU && CPU_32v7 && !CPU_32v6 && !CPU_32v5 && \
		!CPU_32v4 && !CPU_32v3
	help
	  Say Y if you have an ARMv7 processor supporting the LPAE page
	  table format and you would like to access memory beyond the
	  4GB limit. The resulting kernel image will not run on
	  processors without the LPA extension.

	  If unsure, say N.

config ARM_PV_FIXUP
	def_bool y
	depends on ARM_LPAE && ARM_PATCH_PHYS_VIRT && ARCH_KEYSTONE

config ARCH_PHYS_ADDR_T_64BIT
	def_bool ARM_LPAE

config ARCH_DMA_ADDR_T_64BIT
	bool

config ARM_THUMB
	bool "Support Thumb user binaries" if !CPU_THUMBONLY
	depends on CPU_ARM720T || CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || \
		CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || \
		CPU_ARM1020 || CPU_ARM1020E || CPU_ARM1022 || CPU_ARM1026 || \
		CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_V6 || CPU_V6K || \
		CPU_V7 || CPU_FEROCEON || CPU_V7M
	default y
	help
	  Say Y if you want to include kernel support for running user space
	  Thumb binaries.

	  The Thumb instruction set is a compressed form of the standard ARM
	  instruction set resulting in smaller binaries at the expense of
	  slightly less efficient code.

	  If you don't know what this all is, saying Y is a safe choice.

config ARM_THUMBEE
	bool "Enable ThumbEE CPU extension"
	depends on CPU_V7
	help
	  Say Y here if you have a CPU with the ThumbEE extension and code to
	  make use of it. Say N for code that can run on CPUs without ThumbEE.

config ARM_VIRT_EXT
	bool
	depends on MMU
	default y if CPU_V7
	help
	  Enable the kernel to make use of the ARM Virtualization
	  Extensions to install hypervisors without run-time firmware
	  assistance.

	  A compliant bootloader is required in order to make maximum
	  use of this feature.  Refer to Documentation/arm/Booting for
	  details.

config SWP_EMULATE
	bool "Emulate SWP/SWPB instructions" if !SMP
	depends on CPU_V7
	default y if SMP
	select HAVE_PROC_CPU if PROC_FS
	help
	  ARMv6 architecture deprecates use of the SWP/SWPB instructions.
	  ARMv7 multiprocessing extensions introduce the ability to disable
	  these instructions, triggering an undefined instruction exception
	  when executed. Say Y here to enable software emulation of these
	  instructions for userspace (not kernel) using LDREX/STREX.
	  Also creates /proc/cpu/swp_emulation for statistics.

	  In some older versions of glibc [<=2.8] SWP is used during futex
	  trylock() operations with the assumption that the code will not
	  be preempted. This invalid assumption may be more likely to fail
	  with SWP emulation enabled, leading to deadlock of the user
	  application.

	  NOTE: when accessing uncached shared regions, LDREX/STREX rely
	  on an external transaction monitoring block called a global
	  monitor to maintain update atomicity. If your system does not
	  implement a global monitor, this option can cause programs that
	  perform SWP operations to uncached memory to deadlock.

	  If unsure, say Y.

config CPU_BIG_ENDIAN
	bool "Build big-endian kernel"
	depends on ARCH_SUPPORTS_BIG_ENDIAN
	help
	  Say Y if you plan on running a kernel in big-endian mode.
	  Note that your board must be properly built and your board
	  port must properly enable any big-endian related features
	  of your chipset/board/processor.

config CPU_ENDIAN_BE8
	bool
	depends on CPU_BIG_ENDIAN
	default CPU_V6 || CPU_V6K || CPU_V7
	help
	  Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.

config CPU_ENDIAN_BE32
	bool
	depends on CPU_BIG_ENDIAN
	default !CPU_ENDIAN_BE8
	help
	  Support for the BE-32 (big-endian) mode on pre-ARMv6 processors.

config CPU_HIGH_VECTOR
	depends on !MMU && CPU_CP15 && !CPU_ARM740T
	bool "Select the High exception vector"
	help
	  Say Y here to select high exception vector(0xFFFF0000~).
	  The exception vector can vary depending on the platform
	  design in nommu mode. If your platform needs to select
	  high exception vector, say Y.
	  Otherwise or if you are unsure, say N, and the low exception
	  vector (0x00000000~) will be used.

config CPU_ICACHE_DISABLE
	bool "Disable I-Cache (I-bit)"
	depends on CPU_CP15 && !(CPU_ARM720T || CPU_ARM740T || CPU_XSCALE || CPU_XSC3)
	help
	  Say Y here to disable the processor instruction cache. Unless
	  you have a reason not to or are unsure, say N.

config CPU_DCACHE_DISABLE
	bool "Disable D-Cache (C-bit)"
	depends on CPU_CP15 && !SMP
	help
	  Say Y here to disable the processor data cache. Unless
	  you have a reason not to or are unsure, say N.

config CPU_DCACHE_SIZE
	hex
	depends on CPU_ARM740T || CPU_ARM946E
	default 0x00001000 if CPU_ARM740T
	default 0x00002000 # default size for ARM946E-S
	help
	  Some cores are synthesizable to have various sized cache. For
	  ARM946E-S case, it can vary from 0KB to 1MB.
	  To support such cache operations, it is efficient to know the size
	  before compile time.
	  If your SoC is configured to have a different size, define the value
	  here with proper conditions.

config CPU_DCACHE_WRITETHROUGH
	bool "Force write through D-cache"
	depends on (CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || CPU_ARM1020 || CPU_FA526) && !CPU_DCACHE_DISABLE
	default y if CPU_ARM925T
	help
	  Say Y here to use the data cache in writethrough mode. Unless you
	  specifically require this or are unsure, say N.

config CPU_CACHE_ROUND_ROBIN
	bool "Round robin I and D cache replacement algorithm"
	depends on (CPU_ARM926T || CPU_ARM946E || CPU_ARM1020) && (!CPU_ICACHE_DISABLE || !CPU_DCACHE_DISABLE)
	help
	  Say Y here to use the predictable round-robin cache replacement
	  policy.  Unless you specifically require this or are unsure, say N.

config CPU_BPREDICT_DISABLE
	bool "Disable branch prediction"
	depends on CPU_ARM1020 || CPU_V6 || CPU_V6K || CPU_MOHAWK || CPU_XSC3 || CPU_V7 || CPU_FA526
	help
	  Say Y here to disable branch prediction.  If unsure, say N.

config TLS_REG_EMUL
	bool
	select NEED_KUSER_HELPERS
	help
	  An SMP system using a pre-ARMv6 processor (there are apparently
	  a few prototypes like that in existence) and therefore access to
	  that required register must be emulated.

config NEED_KUSER_HELPERS
	bool

config KUSER_HELPERS
	bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
	depends on MMU
	default y
	help
	  Warning: disabling this option may break user programs.

	  Provide kuser helpers in the vector page.  The kernel provides
	  helper code to userspace in read only form at a fixed location
	  in the high vector page to allow userspace to be independent of
	  the CPU type fitted to the system.  This permits binaries to be
	  run on ARMv4 through to ARMv7 without modification.

	  See Documentation/arm/kernel_user_helpers.txt for details.

	  However, the fixed address nature of these helpers can be used
	  by ROP (return orientated programming) authors when creating
	  exploits.

	  If all of the binaries and libraries which run on your platform
	  are built specifically for your platform, and make no use of
	  these helpers, then you can turn this option off to hinder
	  such exploits. However, in that case, if a binary or library
	  relying on those helpers is run, it will receive a SIGILL signal,
	  which will terminate the program.

	  Say N here only if you are absolutely certain that you do not
	  need these helpers; otherwise, the safe option is to say Y.

config VDSO
	bool "Enable VDSO for acceleration of some system calls"
	depends on AEABI && MMU && CPU_V7
	default y if ARM_ARCH_TIMER
	select GENERIC_TIME_VSYSCALL
	help
	  Place in the process address space an ELF shared object
	  providing fast implementations of gettimeofday and
	  clock_gettime.  Systems that implement the ARM architected
	  timer will receive maximum benefit.

	  You must have glibc 2.22 or later for programs to seamlessly
	  take advantage of this.

config DMA_CACHE_RWFO
	bool "Enable read/write for ownership DMA cache maintenance"
	depends on CPU_V6K && SMP
	default y
	help
	  The Snoop Control Unit on ARM11MPCore does not detect the
	  cache maintenance operations and the dma_{map,unmap}_area()
	  functions may leave stale cache entries on other CPUs. By
	  enabling this option, Read or Write For Ownership in the ARMv6
	  DMA cache maintenance functions is performed. These LDR/STR
	  instructions change the cache line state to shared or modified
	  so that the cache operation has the desired effect.

	  Note that the workaround is only valid on processors that do
	  not perform speculative loads into the D-cache. For such
	  processors, if cache maintenance operations are not broadcast
	  in hardware, other workarounds are needed (e.g. cache
	  maintenance broadcasting in software via FIQ).

config OUTER_CACHE
	bool

config OUTER_CACHE_SYNC
	bool
	select ARM_HEAVY_MB
	help
	  The outer cache has a outer_cache_fns.sync function pointer
	  that can be used to drain the write buffer of the outer cache.

config CACHE_FEROCEON_L2
	bool "Enable the Feroceon L2 cache controller"
	depends on ARCH_MV78XX0 || ARCH_MVEBU
	default y
	select OUTER_CACHE
	help
	  This option enables the Feroceon L2 cache controller.

config CACHE_FEROCEON_L2_WRITETHROUGH
	bool "Force Feroceon L2 cache write through"
	depends on CACHE_FEROCEON_L2
	help
	  Say Y here to use the Feroceon L2 cache in writethrough mode.
	  Unless you specifically require this, say N for writeback mode.

config MIGHT_HAVE_CACHE_L2X0
	bool
	help
	  This option should be selected by machines which have a L2x0
	  or PL310 cache controller, but where its use is optional.

	  The only effect of this option is to make CACHE_L2X0 and
	  related options available to the user for configuration.

	  Boards or SoCs which always require the cache controller
	  support to be present should select CACHE_L2X0 directly
	  instead of this option, thus preventing the user from
	  inadvertently configuring a broken kernel.

config CACHE_L2X0
	bool "Enable the L2x0 outer cache controller" if MIGHT_HAVE_CACHE_L2X0
	default MIGHT_HAVE_CACHE_L2X0
	select OUTER_CACHE
	select OUTER_CACHE_SYNC
	help
	  This option enables the L2x0 PrimeCell.

if CACHE_L2X0

config PL310_ERRATA_588369
	bool "PL310 errata: Clean & Invalidate maintenance operations do not invalidate clean lines"
	help
	   The PL310 L2 cache controller implements three types of Clean &
	   Invalidate maintenance operations: by Physical Address
	   (offset 0x7F0), by Index/Way (0x7F8) and by Way (0x7FC).
	   They are architecturally defined to behave as the execution of a
	   clean operation followed immediately by an invalidate operation,
	   both performing to the same memory location. This functionality
	   is not correctly implemented in PL310 prior to r2p0 (fixed in r2p0)
	   as clean lines are not invalidated as a result of these operations.

config PL310_ERRATA_727915
	bool "PL310 errata: Background Clean & Invalidate by Way operation can cause data corruption"
	help
	  PL310 implements the Clean & Invalidate by Way L2 cache maintenance
	  operation (offset 0x7FC). This operation runs in background so that
	  PL310 can handle normal accesses while it is in progress. Under very
	  rare circumstances, due to this erratum, write data can be lost when
	  PL310 treats a cacheable write transaction during a Clean &
	  Invalidate by Way operation.  Revisions prior to r3p1 are affected by
	  this errata (fixed in r3p1).

config PL310_ERRATA_753970
	bool "PL310 errata: cache sync operation may be faulty"
	help
	  This option enables the workaround for the 753970 PL310 (r3p0) erratum.

	  Under some condition the effect of cache sync operation on
	  the store buffer still remains when the operation completes.
	  This means that the store buffer is always asked to drain and
	  this prevents it from merging any further writes. The workaround
	  is to replace the normal offset of cache sync operation (0x730)
	  by another offset targeting an unmapped PL310 register 0x740.
	  This has the same effect as the cache sync operation: store buffer
	  drain and waiting for all buffers empty.

config PL310_ERRATA_769419
	bool "PL310 errata: no automatic Store Buffer drain"
	help
	  On revisions of the PL310 prior to r3p2, the Store Buffer does
	  not automatically drain. This can cause normal, non-cacheable
	  writes to be retained when the memory system is idle, leading
	  to suboptimal I/O performance for drivers using coherent DMA.
	  This option adds a write barrier to the cpu_idle loop so that,
	  on systems with an outer cache, the store buffer is drained
	  explicitly.

endif

config CACHE_TAUROS2
	bool "Enable the Tauros2 L2 cache controller"
	depends on (ARCH_DOVE || ARCH_MMP || CPU_PJ4)
	default y
	select OUTER_CACHE
	help
	  This option enables the Tauros2 L2 cache controller (as
	  found on PJ1/PJ4).

config CACHE_UNIPHIER
	bool "Enable the UniPhier outer cache controller"
	depends on ARCH_UNIPHIER
	default y
	select OUTER_CACHE
	select OUTER_CACHE_SYNC
	help
	  This option enables the UniPhier outer cache (system cache)
	  controller.

config CACHE_XSC3L2
	bool "Enable the L2 cache on XScale3"
	depends on CPU_XSC3
	default y
	select OUTER_CACHE
	help
	  This option enables the L2 cache on XScale3.

config ARM_L1_CACHE_SHIFT_6
	bool
	default y if CPU_V7
	help
	  Setting ARM L1 cache line size to 64 Bytes.

config ARM_L1_CACHE_SHIFT
	int
	default 6 if ARM_L1_CACHE_SHIFT_6
	default 5

config ARM_DMA_MEM_BUFFERABLE
	bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
	default y if CPU_V6 || CPU_V6K || CPU_V7
	help
	  Historically, the kernel has used strongly ordered mappings to
	  provide DMA coherent memory.  With the advent of ARMv7, mapping
	  memory with differing types results in unpredictable behaviour,
	  so on these CPUs, this option is forced on.

	  Multiple mappings with differing attributes is also unpredictable
	  on ARMv6 CPUs, but since they do not have aggressive speculative
	  prefetch, no harm appears to occur.

	  However, drivers may be missing the necessary barriers for ARMv6,
	  and therefore turning this on may result in unpredictable driver
	  behaviour.  Therefore, we offer this as an option.

	  You are recommended say 'Y' here and debug any affected drivers.

config ARCH_HAS_BARRIERS
	bool
	help
	  This option allows the use of custom mandatory barriers
	  included via the mach/barriers.h file.

config ARM_HEAVY_MB
	bool

config ARCH_SUPPORTS_BIG_ENDIAN
	bool
	help
	  This option specifies the architecture can support big endian
	  operation.

config ARM_KERNMEM_PERMS
	bool "Restrict kernel memory permissions"
	depends on MMU
	help
	  If this is set, kernel memory other than kernel text (and rodata)
	  will be made non-executable. The tradeoff is that each region is
	  padded to section-size (1MiB) boundaries (because their permissions
	  are different and splitting the 1M pages into 4K ones causes TLB
	  performance problems), wasting memory.

config DEBUG_RODATA
	bool "Make kernel text and rodata read-only"
	depends on ARM_KERNMEM_PERMS
	default y
	help
	  If this is set, kernel text and rodata will be made read-only. This
	  is to help catch accidental or malicious attempts to change the
	  kernel's executable code. Additionally splits rodata from kernel
	  text so it can be made explicitly non-executable. This creates
	  another section-size padded region, so it can waste more memory
	  space while gaining the read-only protections.