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. # ARM610 config CPU_ARM610 bool "Support ARM610 processor" if ARCH_RPC select CPU_32v3 select CPU_CACHE_V3 select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V3 if MMU select CPU_TLB_V3 if MMU select CPU_PABRT_LEGACY help The ARM610 is the successor to the ARM3 processor and was produced by VLSI Technology Inc. Say Y if you want support for the ARM610 processor. Otherwise, say N. # ARM7TDMI config CPU_ARM7TDMI bool "Support ARM7TDMI processor" depends on !MMU select CPU_32v4T select CPU_ABRT_LV4T select CPU_PABRT_LEGACY select CPU_CACHE_V4 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. # ARM710 config CPU_ARM710 bool "Support ARM710 processor" if ARCH_RPC select CPU_32v3 select CPU_CACHE_V3 select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V3 if MMU select CPU_TLB_V3 if MMU select CPU_PABRT_LEGACY help A 32-bit RISC microprocessor based on the ARM7 processor core designed by Advanced RISC Machines Ltd. The ARM710 is the successor to the ARM610 processor. It was released in July 1994 by VLSI Technology Inc. Say Y if you want support for the ARM710 processor. Otherwise, say N. # ARM720T config CPU_ARM720T bool "Support ARM720T processor" if ARCH_INTEGRATOR select CPU_32v4T select CPU_ABRT_LV4T select CPU_PABRT_LEGACY select CPU_CACHE_V4 select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WT if MMU 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 "Support ARM740T processor" if ARCH_INTEGRATOR depends on !MMU select CPU_32v4T select CPU_ABRT_LV4T select CPU_PABRT_LEGACY select CPU_CACHE_V3 # although the core is v4t select CPU_CP15_MPU 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 "Support ARM9TDMI processor" depends on !MMU select CPU_32v4T select CPU_ABRT_NOMMU select CPU_PABRT_LEGACY select CPU_CACHE_V4 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 "Support ARM920T processor" if ARCH_INTEGRATOR select CPU_32v4T select CPU_ABRT_EV4T select CPU_PABRT_LEGACY select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU 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 "Support ARM922T processor" if ARCH_INTEGRATOR select CPU_32v4T select CPU_ABRT_EV4T select CPU_PABRT_LEGACY select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU 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 "Support ARM925T processor" if ARCH_OMAP1 select CPU_32v4T select CPU_ABRT_EV4T select CPU_PABRT_LEGACY select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU 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 "Support ARM926T processor" if ARCH_INTEGRATOR || MACH_REALVIEW_EB select CPU_32v5 select CPU_ABRT_EV5TJ select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU 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_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_CACHE_FA select CPU_COPY_FA if MMU 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 "Support ARM940T processor" if ARCH_INTEGRATOR depends on !MMU select CPU_32v4T select CPU_ABRT_NOMMU select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MPU 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 "Support ARM946E-S processor" if ARCH_INTEGRATOR depends on !MMU select CPU_32v5 select CPU_ABRT_NOMMU select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MPU 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 "Support ARM1020T (rev 0) processor" if ARCH_INTEGRATOR select CPU_32v5 select CPU_ABRT_EV4T select CPU_PABRT_LEGACY select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU 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 "Support ARM1020E processor" if ARCH_INTEGRATOR select CPU_32v5 select CPU_ABRT_EV4T select CPU_PABRT_LEGACY select CPU_CACHE_V4WT select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU select CPU_TLB_V4WBI if MMU depends on n # ARM1022E config CPU_ARM1022 bool "Support ARM1022E processor" if ARCH_INTEGRATOR select CPU_32v5 select CPU_ABRT_EV4T select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU # can probably do better 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 "Support ARM1026EJ-S processor" if ARCH_INTEGRATOR select CPU_32v5 select CPU_ABRT_EV5T # But need Jazelle, but EV5TJ ignores bit 10 select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU # can probably do better 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 "Support StrongARM(R) SA-110 processor" if ARCH_RPC select CPU_32v3 if ARCH_RPC select CPU_32v4 if !ARCH_RPC select CPU_ABRT_EV4 select CPU_PABRT_LEGACY select CPU_CACHE_V4WB select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_V4WB if MMU 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 . 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_PABRT_LEGACY select CPU_CACHE_V4WB select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_TLB_V4WB if MMU # XScale config CPU_XSCALE bool select CPU_32v5 select CPU_ABRT_EV5T select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_TLB_V4WBI if MMU # XScale Core Version 3 config CPU_XSC3 bool select CPU_32v5 select CPU_ABRT_EV5T select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU 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_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_TLB_V4WBI if MMU select CPU_COPY_V4WB if MMU # Feroceon config CPU_FEROCEON bool select CPU_32v5 select CPU_ABRT_EV5T select CPU_PABRT_LEGACY select CPU_CACHE_VIVT select CPU_CP15_MMU select CPU_COPY_FEROCEON if MMU 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 CPU_V7 select ARM_THUMBEE # ARMv6 config CPU_V6 bool "Support ARM V6 processor" if ARCH_INTEGRATOR || MACH_REALVIEW_EB || MACH_REALVIEW_PBX select CPU_32v6 select CPU_ABRT_EV6 select CPU_PABRT_V6 select CPU_CACHE_V6 select CPU_CACHE_VIPT select CPU_CP15_MMU select CPU_HAS_ASID if MMU select CPU_COPY_V6 if MMU select CPU_TLB_V6 if MMU # ARMv6k config CPU_V6K bool "Support ARM V6K processor" if ARCH_INTEGRATOR || MACH_REALVIEW_EB || MACH_REALVIEW_PBX select CPU_32v6 select CPU_32v6K select CPU_ABRT_EV6 select CPU_PABRT_V6 select CPU_CACHE_V6 select CPU_CACHE_VIPT select CPU_CP15_MMU select CPU_HAS_ASID if MMU select CPU_COPY_V6 if MMU select CPU_TLB_V6 if MMU # ARMv7 config CPU_V7 bool "Support ARM V7 processor" if ARCH_INTEGRATOR || MACH_REALVIEW_EB || MACH_REALVIEW_PBX select CPU_32v6K select CPU_32v7 select CPU_ABRT_EV7 select CPU_PABRT_V7 select CPU_CACHE_V7 select CPU_CACHE_VIPT select CPU_CP15_MMU select CPU_HAS_ASID if MMU select CPU_COPY_V6 if MMU select CPU_TLB_V7 if MMU # 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 TLS_REG_EMUL if SMP || !MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select CPU_USE_DOMAINS if MMU config CPU_32v4 bool select TLS_REG_EMUL if SMP || !MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select CPU_USE_DOMAINS if MMU config CPU_32v4T bool select TLS_REG_EMUL if SMP || !MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select CPU_USE_DOMAINS if MMU config CPU_32v5 bool select TLS_REG_EMUL if SMP || !MMU select NEEDS_SYSCALL_FOR_CMPXCHG if SMP select CPU_USE_DOMAINS if MMU config CPU_32v6 bool select TLS_REG_EMUL if !CPU_32v6K && !MMU select CPU_USE_DOMAINS if CPU_V6 && MMU config CPU_32v6K bool config CPU_32v7 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_V3 bool 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_VIVT bool config CPU_CACHE_VIPT bool config CPU_CACHE_FA bool if MMU # The copy-page model config CPU_COPY_V3 bool 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_V3 bool help ARM Architecture Version 3 TLB. 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. # # CPU supports 36-bit I/O # config IO_36 bool comment "Processor Features" config ARM_THUMB bool "Support Thumb user binaries" 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 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 SWP_EMULATE bool "Emulate SWP/SWPB instructions" depends on CPU_V7 select HAVE_PROC_CPU if PROC_FS default y if SMP 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 be 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_ARM610 || CPU_ARM710 || 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 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 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 NEEDS_SYSCALL_FOR_CMPXCHG bool help SMP on a pre-ARMv6 processor? Well OK then. Forget about fast user space cmpxchg support. It is just not possible. 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 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_KIRKWOOD || ARCH_MV78XX0 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 CACHE_L2X0 bool "Enable the L2x0 outer cache controller" depends on REALVIEW_EB_ARM11MP || MACH_REALVIEW_PB11MP || MACH_REALVIEW_PB1176 || \ REALVIEW_EB_A9MP || ARCH_MX35 || ARCH_MX31 || MACH_REALVIEW_PBX || \ ARCH_NOMADIK || ARCH_OMAP4 || ARCH_S5PV310 || ARCH_TEGRA || \ ARCH_U8500 || ARCH_VEXPRESS_CA9X4 || ARCH_SHMOBILE default y select OUTER_CACHE select OUTER_CACHE_SYNC help This option enables the L2x0 PrimeCell. config CACHE_PL310 bool depends on CACHE_L2X0 default y if CPU_V7 && !(CPU_V6 || CPU_V6K) help This option enables optimisations for the PL310 cache controller. 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_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 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 depends on !(MACH_REALVIEW_PB1176 || REALVIEW_EB_ARM11MP || \ MACH_REALVIEW_PB11MP) 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.