1 comment "Processor Type"
3 # Select CPU types depending on the architecture selected. This selects
4 # which CPUs we support in the kernel image, and the compiler instruction
9 bool "Support ARM7TDMI processor"
14 select CPU_PABRT_LEGACY
16 A 32-bit RISC microprocessor based on the ARM7 processor core
17 which has no memory control unit and cache.
19 Say Y if you want support for the ARM7TDMI processor.
24 bool "Support ARM720T processor" if (ARCH_MULTI_V4T && ARCH_INTEGRATOR)
29 select CPU_COPY_V4WT if MMU
31 select CPU_PABRT_LEGACY
32 select CPU_TLB_V4WT if MMU
34 A 32-bit RISC processor with 8kByte Cache, Write Buffer and
35 MMU built around an ARM7TDMI core.
37 Say Y if you want support for the ARM720T processor.
42 bool "Support ARM740T processor" if (ARCH_MULTI_V4T && ARCH_INTEGRATOR)
48 select CPU_PABRT_LEGACY
50 A 32-bit RISC processor with 8KB cache or 4KB variants,
51 write buffer and MPU(Protection Unit) built around
54 Say Y if you want support for the ARM740T processor.
59 bool "Support ARM9TDMI processor"
64 select CPU_PABRT_LEGACY
66 A 32-bit RISC microprocessor based on the ARM9 processor core
67 which has no memory control unit and cache.
69 Say Y if you want support for the ARM9TDMI processor.
74 bool "Support ARM920T processor" if (ARCH_MULTI_V4T && ARCH_INTEGRATOR)
79 select CPU_COPY_V4WB if MMU
81 select CPU_PABRT_LEGACY
82 select CPU_TLB_V4WBI if MMU
84 The ARM920T is licensed to be produced by numerous vendors,
85 and is used in the Cirrus EP93xx and the Samsung S3C2410.
87 Say Y if you want support for the ARM920T processor.
92 bool "Support ARM922T processor" if (ARCH_MULTI_V4T && ARCH_INTEGRATOR)
97 select CPU_COPY_V4WB if MMU
99 select CPU_PABRT_LEGACY
100 select CPU_TLB_V4WBI if MMU
102 The ARM922T is a version of the ARM920T, but with smaller
103 instruction and data caches. It is used in Altera's
104 Excalibur XA device family and Micrel's KS8695 Centaur.
106 Say Y if you want support for the ARM922T processor.
111 bool "Support ARM925T processor" if ARCH_OMAP1
114 select CPU_CACHE_V4WT
115 select CPU_CACHE_VIVT
116 select CPU_COPY_V4WB if MMU
118 select CPU_PABRT_LEGACY
119 select CPU_TLB_V4WBI if MMU
121 The ARM925T is a mix between the ARM920T and ARM926T, but with
122 different instruction and data caches. It is used in TI's OMAP
125 Say Y if you want support for the ARM925T processor.
130 bool "Support ARM926T processor" if (!ARCH_MULTIPLATFORM || ARCH_MULTI_V5) && (ARCH_INTEGRATOR || MACH_REALVIEW_EB)
132 select CPU_ABRT_EV5TJ
133 select CPU_CACHE_VIVT
134 select CPU_COPY_V4WB if MMU
136 select CPU_PABRT_LEGACY
137 select CPU_TLB_V4WBI if MMU
139 This is a variant of the ARM920. It has slightly different
140 instruction sequences for cache and TLB operations. Curiously,
141 there is no documentation on it at the ARM corporate website.
143 Say Y if you want support for the ARM926T processor.
152 select CPU_CACHE_VIVT
153 select CPU_COPY_FA if MMU
155 select CPU_PABRT_LEGACY
156 select CPU_TLB_FA if MMU
158 The FA526 is a version of the ARMv4 compatible processor with
159 Branch Target Buffer, Unified TLB and cache line size 16.
161 Say Y if you want support for the FA526 processor.
166 bool "Support ARM940T processor" if (ARCH_MULTI_V4T && ARCH_INTEGRATOR)
169 select CPU_ABRT_NOMMU
170 select CPU_CACHE_VIVT
172 select CPU_PABRT_LEGACY
174 ARM940T is a member of the ARM9TDMI family of general-
175 purpose microprocessors with MPU and separate 4KB
176 instruction and 4KB data cases, each with a 4-word line
179 Say Y if you want support for the ARM940T processor.
184 bool "Support ARM946E-S processor" if (ARCH_MULTI_V5 && ARCH_INTEGRATOR)
187 select CPU_ABRT_NOMMU
188 select CPU_CACHE_VIVT
190 select CPU_PABRT_LEGACY
192 ARM946E-S is a member of the ARM9E-S family of high-
193 performance, 32-bit system-on-chip processor solutions.
194 The TCM and ARMv5TE 32-bit instruction set is supported.
196 Say Y if you want support for the ARM946E-S processor.
199 # ARM1020 - needs validating
201 bool "Support ARM1020T (rev 0) processor" if (ARCH_MULTI_V5 && ARCH_INTEGRATOR)
204 select CPU_CACHE_V4WT
205 select CPU_CACHE_VIVT
206 select CPU_COPY_V4WB if MMU
208 select CPU_PABRT_LEGACY
209 select CPU_TLB_V4WBI if MMU
211 The ARM1020 is the 32K cached version of the ARM10 processor,
212 with an addition of a floating-point unit.
214 Say Y if you want support for the ARM1020 processor.
217 # ARM1020E - needs validating
219 bool "Support ARM1020E processor" if (ARCH_MULTI_V5 && ARCH_INTEGRATOR)
223 select CPU_CACHE_V4WT
224 select CPU_CACHE_VIVT
225 select CPU_COPY_V4WB if MMU
227 select CPU_PABRT_LEGACY
228 select CPU_TLB_V4WBI if MMU
232 bool "Support ARM1022E processor" if (ARCH_MULTI_V5 && ARCH_INTEGRATOR)
235 select CPU_CACHE_VIVT
236 select CPU_COPY_V4WB if MMU # can probably do better
238 select CPU_PABRT_LEGACY
239 select CPU_TLB_V4WBI if MMU
241 The ARM1022E is an implementation of the ARMv5TE architecture
242 based upon the ARM10 integer core with a 16KiB L1 Harvard cache,
243 embedded trace macrocell, and a floating-point unit.
245 Say Y if you want support for the ARM1022E processor.
250 bool "Support ARM1026EJ-S processor" if (ARCH_MULTI_V5 && ARCH_INTEGRATOR)
252 select CPU_ABRT_EV5T # But need Jazelle, but EV5TJ ignores bit 10
253 select CPU_CACHE_VIVT
254 select CPU_COPY_V4WB if MMU # can probably do better
256 select CPU_PABRT_LEGACY
257 select CPU_TLB_V4WBI if MMU
259 The ARM1026EJ-S is an implementation of the ARMv5TEJ architecture
260 based upon the ARM10 integer core.
262 Say Y if you want support for the ARM1026EJ-S processor.
268 select CPU_32v3 if ARCH_RPC
269 select CPU_32v4 if !ARCH_RPC
271 select CPU_CACHE_V4WB
272 select CPU_CACHE_VIVT
273 select CPU_COPY_V4WB if MMU
275 select CPU_PABRT_LEGACY
276 select CPU_TLB_V4WB if MMU
278 The Intel StrongARM(R) SA-110 is a 32-bit microprocessor and
279 is available at five speeds ranging from 100 MHz to 233 MHz.
280 More information is available at
281 <http://developer.intel.com/design/strong/sa110.htm>.
283 Say Y if you want support for the SA-110 processor.
291 select CPU_CACHE_V4WB
292 select CPU_CACHE_VIVT
294 select CPU_PABRT_LEGACY
295 select CPU_TLB_V4WB if MMU
302 select CPU_CACHE_VIVT
304 select CPU_PABRT_LEGACY
305 select CPU_TLB_V4WBI if MMU
307 # XScale Core Version 3
312 select CPU_CACHE_VIVT
314 select CPU_PABRT_LEGACY
315 select CPU_TLB_V4WBI if MMU
318 # Marvell PJ1 (Mohawk)
323 select CPU_CACHE_VIVT
324 select CPU_COPY_V4WB if MMU
326 select CPU_PABRT_LEGACY
327 select CPU_TLB_V4WBI if MMU
334 select CPU_CACHE_VIVT
335 select CPU_COPY_FEROCEON if MMU
337 select CPU_PABRT_LEGACY
338 select CPU_TLB_FEROCEON if MMU
340 config CPU_FEROCEON_OLD_ID
341 bool "Accept early Feroceon cores with an ARM926 ID"
342 depends on CPU_FEROCEON && !CPU_ARM926T
345 This enables the usage of some old Feroceon cores
346 for which the CPU ID is equal to the ARM926 ID.
347 Relevant for Feroceon-1850 and early Feroceon-2850.
361 bool "Support ARM V6 processor" if (!ARCH_MULTIPLATFORM || ARCH_MULTI_V6) && (ARCH_INTEGRATOR || MACH_REALVIEW_EB || MACH_REALVIEW_PBX)
365 select CPU_CACHE_VIPT
366 select CPU_COPY_V6 if MMU
368 select CPU_HAS_ASID if MMU
370 select CPU_TLB_V6 if MMU
374 bool "Support ARM V6K processor" if (!ARCH_MULTIPLATFORM || ARCH_MULTI_V6) && (ARCH_INTEGRATOR || MACH_REALVIEW_EB || MACH_REALVIEW_PBX)
379 select CPU_CACHE_VIPT
380 select CPU_COPY_V6 if MMU
382 select CPU_HAS_ASID if MMU
384 select CPU_TLB_V6 if MMU
388 bool "Support ARM V7 processor" if (!ARCH_MULTIPLATFORM || ARCH_MULTI_V7) && (ARCH_INTEGRATOR || MACH_REALVIEW_EB || MACH_REALVIEW_PBX)
393 select CPU_CACHE_VIPT
394 select CPU_COPY_V6 if MMU
395 select CPU_CP15_MMU if MMU
396 select CPU_CP15_MPU if !MMU
397 select CPU_HAS_ASID if MMU
399 select CPU_TLB_V7 if MMU
405 select CPU_ABRT_NOMMU
407 select CPU_PABRT_LEGACY
412 # There are no CPUs available with MMU that don't implement an ARM ISA:
415 Select this if your CPU doesn't support the 32 bit ARM instructions.
417 # Figure out what processor architecture version we should be using.
418 # This defines the compiler instruction set which depends on the machine type.
421 select CPU_USE_DOMAINS if MMU
422 select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
423 select NEED_KUSER_HELPERS
424 select TLS_REG_EMUL if SMP || !MMU
428 select CPU_USE_DOMAINS if MMU
429 select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
430 select NEED_KUSER_HELPERS
431 select TLS_REG_EMUL if SMP || !MMU
435 select CPU_USE_DOMAINS if MMU
436 select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
437 select NEED_KUSER_HELPERS
438 select TLS_REG_EMUL if SMP || !MMU
442 select CPU_USE_DOMAINS if MMU
443 select NEEDS_SYSCALL_FOR_CMPXCHG if SMP
444 select NEED_KUSER_HELPERS
445 select TLS_REG_EMUL if SMP || !MMU
449 select TLS_REG_EMUL if !CPU_32v6K && !MMU
461 config CPU_ABRT_NOMMU
476 config CPU_ABRT_EV5TJ
485 config CPU_PABRT_LEGACY
498 config CPU_CACHE_V4WT
501 config CPU_CACHE_V4WB
513 config CPU_CACHE_VIVT
516 config CPU_CACHE_VIPT
523 # The copy-page model
530 config CPU_COPY_FEROCEON
539 # This selects the TLB model
543 ARM Architecture Version 4 TLB with writethrough cache.
548 ARM Architecture Version 4 TLB with writeback cache.
553 ARM Architecture Version 4 TLB with writeback cache and invalidate
554 instruction cache entry.
556 config CPU_TLB_FEROCEON
559 Feroceon TLB (v4wbi with non-outer-cachable page table walks).
564 Faraday ARM FA526 architecture, unified TLB with writeback cache
565 and invalidate instruction cache entry. Branch target buffer is
574 config VERIFY_PERMISSION_FAULT
581 This indicates whether the CPU has the ASID register; used to
582 tag TLB and possibly cache entries.
587 Processor has the CP15 register.
593 Processor has the CP15 register, which has MMU related registers.
599 Processor has the CP15 register, which has MPU related registers.
601 config CPU_USE_DOMAINS
604 This option enables or disables the use of domain switching
605 via the set_fs() function.
608 # CPU supports 36-bit I/O
613 comment "Processor Features"
616 bool "Support for the Large Physical Address Extension"
617 depends on MMU && CPU_32v7 && !CPU_32v6 && !CPU_32v5 && \
618 !CPU_32v4 && !CPU_32v3
620 Say Y if you have an ARMv7 processor supporting the LPAE page
621 table format and you would like to access memory beyond the
622 4GB limit. The resulting kernel image will not run on
623 processors without the LPA extension.
629 depends on ARM_LPAE && ARM_PATCH_PHYS_VIRT && ARCH_KEYSTONE
631 config ARCH_PHYS_ADDR_T_64BIT
634 config ARCH_DMA_ADDR_T_64BIT
638 bool "Support Thumb user binaries" if !CPU_THUMBONLY
639 depends on CPU_ARM720T || CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || \
640 CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || \
641 CPU_ARM1020 || CPU_ARM1020E || CPU_ARM1022 || CPU_ARM1026 || \
642 CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_V6 || CPU_V6K || \
643 CPU_V7 || CPU_FEROCEON || CPU_V7M
646 Say Y if you want to include kernel support for running user space
649 The Thumb instruction set is a compressed form of the standard ARM
650 instruction set resulting in smaller binaries at the expense of
651 slightly less efficient code.
653 If you don't know what this all is, saying Y is a safe choice.
656 bool "Enable ThumbEE CPU extension"
659 Say Y here if you have a CPU with the ThumbEE extension and code to
660 make use of it. Say N for code that can run on CPUs without ThumbEE.
667 Enable the kernel to make use of the ARM Virtualization
668 Extensions to install hypervisors without run-time firmware
671 A compliant bootloader is required in order to make maximum
672 use of this feature. Refer to Documentation/arm/Booting for
676 bool "Emulate SWP/SWPB instructions" if !SMP
679 select HAVE_PROC_CPU if PROC_FS
681 ARMv6 architecture deprecates use of the SWP/SWPB instructions.
682 ARMv7 multiprocessing extensions introduce the ability to disable
683 these instructions, triggering an undefined instruction exception
684 when executed. Say Y here to enable software emulation of these
685 instructions for userspace (not kernel) using LDREX/STREX.
686 Also creates /proc/cpu/swp_emulation for statistics.
688 In some older versions of glibc [<=2.8] SWP is used during futex
689 trylock() operations with the assumption that the code will not
690 be preempted. This invalid assumption may be more likely to fail
691 with SWP emulation enabled, leading to deadlock of the user
694 NOTE: when accessing uncached shared regions, LDREX/STREX rely
695 on an external transaction monitoring block called a global
696 monitor to maintain update atomicity. If your system does not
697 implement a global monitor, this option can cause programs that
698 perform SWP operations to uncached memory to deadlock.
702 config CPU_BIG_ENDIAN
703 bool "Build big-endian kernel"
704 depends on ARCH_SUPPORTS_BIG_ENDIAN
706 Say Y if you plan on running a kernel in big-endian mode.
707 Note that your board must be properly built and your board
708 port must properly enable any big-endian related features
709 of your chipset/board/processor.
711 config CPU_ENDIAN_BE8
713 depends on CPU_BIG_ENDIAN
714 default CPU_V6 || CPU_V6K || CPU_V7
716 Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.
718 config CPU_ENDIAN_BE32
720 depends on CPU_BIG_ENDIAN
721 default !CPU_ENDIAN_BE8
723 Support for the BE-32 (big-endian) mode on pre-ARMv6 processors.
725 config CPU_HIGH_VECTOR
726 depends on !MMU && CPU_CP15 && !CPU_ARM740T
727 bool "Select the High exception vector"
729 Say Y here to select high exception vector(0xFFFF0000~).
730 The exception vector can vary depending on the platform
731 design in nommu mode. If your platform needs to select
732 high exception vector, say Y.
733 Otherwise or if you are unsure, say N, and the low exception
734 vector (0x00000000~) will be used.
736 config CPU_ICACHE_DISABLE
737 bool "Disable I-Cache (I-bit)"
738 depends on CPU_CP15 && !(CPU_ARM720T || CPU_ARM740T || CPU_XSCALE || CPU_XSC3)
740 Say Y here to disable the processor instruction cache. Unless
741 you have a reason not to or are unsure, say N.
743 config CPU_DCACHE_DISABLE
744 bool "Disable D-Cache (C-bit)"
745 depends on CPU_CP15 && !SMP
747 Say Y here to disable the processor data cache. Unless
748 you have a reason not to or are unsure, say N.
750 config CPU_DCACHE_SIZE
752 depends on CPU_ARM740T || CPU_ARM946E
753 default 0x00001000 if CPU_ARM740T
754 default 0x00002000 # default size for ARM946E-S
756 Some cores are synthesizable to have various sized cache. For
757 ARM946E-S case, it can vary from 0KB to 1MB.
758 To support such cache operations, it is efficient to know the size
760 If your SoC is configured to have a different size, define the value
761 here with proper conditions.
763 config CPU_DCACHE_WRITETHROUGH
764 bool "Force write through D-cache"
765 depends on (CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || CPU_ARM1020 || CPU_FA526) && !CPU_DCACHE_DISABLE
766 default y if CPU_ARM925T
768 Say Y here to use the data cache in writethrough mode. Unless you
769 specifically require this or are unsure, say N.
771 config CPU_CACHE_ROUND_ROBIN
772 bool "Round robin I and D cache replacement algorithm"
773 depends on (CPU_ARM926T || CPU_ARM946E || CPU_ARM1020) && (!CPU_ICACHE_DISABLE || !CPU_DCACHE_DISABLE)
775 Say Y here to use the predictable round-robin cache replacement
776 policy. Unless you specifically require this or are unsure, say N.
778 config CPU_BPREDICT_DISABLE
779 bool "Disable branch prediction"
780 depends on CPU_ARM1020 || CPU_V6 || CPU_V6K || CPU_MOHAWK || CPU_XSC3 || CPU_V7 || CPU_FA526
782 Say Y here to disable branch prediction. If unsure, say N.
786 select NEED_KUSER_HELPERS
788 An SMP system using a pre-ARMv6 processor (there are apparently
789 a few prototypes like that in existence) and therefore access to
790 that required register must be emulated.
792 config NEEDS_SYSCALL_FOR_CMPXCHG
794 select NEED_KUSER_HELPERS
796 SMP on a pre-ARMv6 processor? Well OK then.
797 Forget about fast user space cmpxchg support.
798 It is just not possible.
800 config NEED_KUSER_HELPERS
804 bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
808 Warning: disabling this option may break user programs.
810 Provide kuser helpers in the vector page. The kernel provides
811 helper code to userspace in read only form at a fixed location
812 in the high vector page to allow userspace to be independent of
813 the CPU type fitted to the system. This permits binaries to be
814 run on ARMv4 through to ARMv7 without modification.
816 See Documentation/arm/kernel_user_helpers.txt for details.
818 However, the fixed address nature of these helpers can be used
819 by ROP (return orientated programming) authors when creating
822 If all of the binaries and libraries which run on your platform
823 are built specifically for your platform, and make no use of
824 these helpers, then you can turn this option off to hinder
825 such exploits. However, in that case, if a binary or library
826 relying on those helpers is run, it will receive a SIGILL signal,
827 which will terminate the program.
829 Say N here only if you are absolutely certain that you do not
830 need these helpers; otherwise, the safe option is to say Y.
833 bool "Enable VDSO for acceleration of some system calls"
834 depends on AEABI && MMU && CPU_V7
835 default y if ARM_ARCH_TIMER
836 select GENERIC_TIME_VSYSCALL
838 Place in the process address space an ELF shared object
839 providing fast implementations of gettimeofday and
840 clock_gettime. Systems that implement the ARM architected
841 timer will receive maximum benefit.
843 You must have glibc 2.22 or later for programs to seamlessly
844 take advantage of this.
846 config DMA_CACHE_RWFO
847 bool "Enable read/write for ownership DMA cache maintenance"
848 depends on CPU_V6K && SMP
851 The Snoop Control Unit on ARM11MPCore does not detect the
852 cache maintenance operations and the dma_{map,unmap}_area()
853 functions may leave stale cache entries on other CPUs. By
854 enabling this option, Read or Write For Ownership in the ARMv6
855 DMA cache maintenance functions is performed. These LDR/STR
856 instructions change the cache line state to shared or modified
857 so that the cache operation has the desired effect.
859 Note that the workaround is only valid on processors that do
860 not perform speculative loads into the D-cache. For such
861 processors, if cache maintenance operations are not broadcast
862 in hardware, other workarounds are needed (e.g. cache
863 maintenance broadcasting in software via FIQ).
868 config OUTER_CACHE_SYNC
871 The outer cache has a outer_cache_fns.sync function pointer
872 that can be used to drain the write buffer of the outer cache.
874 config CACHE_FEROCEON_L2
875 bool "Enable the Feroceon L2 cache controller"
876 depends on ARCH_MV78XX0 || ARCH_MVEBU
880 This option enables the Feroceon L2 cache controller.
882 config CACHE_FEROCEON_L2_WRITETHROUGH
883 bool "Force Feroceon L2 cache write through"
884 depends on CACHE_FEROCEON_L2
886 Say Y here to use the Feroceon L2 cache in writethrough mode.
887 Unless you specifically require this, say N for writeback mode.
889 config MIGHT_HAVE_CACHE_L2X0
892 This option should be selected by machines which have a L2x0
893 or PL310 cache controller, but where its use is optional.
895 The only effect of this option is to make CACHE_L2X0 and
896 related options available to the user for configuration.
898 Boards or SoCs which always require the cache controller
899 support to be present should select CACHE_L2X0 directly
900 instead of this option, thus preventing the user from
901 inadvertently configuring a broken kernel.
904 bool "Enable the L2x0 outer cache controller" if MIGHT_HAVE_CACHE_L2X0
905 default MIGHT_HAVE_CACHE_L2X0
907 select OUTER_CACHE_SYNC
909 This option enables the L2x0 PrimeCell.
913 config PL310_ERRATA_588369
914 bool "PL310 errata: Clean & Invalidate maintenance operations do not invalidate clean lines"
916 The PL310 L2 cache controller implements three types of Clean &
917 Invalidate maintenance operations: by Physical Address
918 (offset 0x7F0), by Index/Way (0x7F8) and by Way (0x7FC).
919 They are architecturally defined to behave as the execution of a
920 clean operation followed immediately by an invalidate operation,
921 both performing to the same memory location. This functionality
922 is not correctly implemented in PL310 prior to r2p0 (fixed in r2p0)
923 as clean lines are not invalidated as a result of these operations.
925 config PL310_ERRATA_727915
926 bool "PL310 errata: Background Clean & Invalidate by Way operation can cause data corruption"
928 PL310 implements the Clean & Invalidate by Way L2 cache maintenance
929 operation (offset 0x7FC). This operation runs in background so that
930 PL310 can handle normal accesses while it is in progress. Under very
931 rare circumstances, due to this erratum, write data can be lost when
932 PL310 treats a cacheable write transaction during a Clean &
933 Invalidate by Way operation. Revisions prior to r3p1 are affected by
934 this errata (fixed in r3p1).
936 config PL310_ERRATA_753970
937 bool "PL310 errata: cache sync operation may be faulty"
939 This option enables the workaround for the 753970 PL310 (r3p0) erratum.
941 Under some condition the effect of cache sync operation on
942 the store buffer still remains when the operation completes.
943 This means that the store buffer is always asked to drain and
944 this prevents it from merging any further writes. The workaround
945 is to replace the normal offset of cache sync operation (0x730)
946 by another offset targeting an unmapped PL310 register 0x740.
947 This has the same effect as the cache sync operation: store buffer
948 drain and waiting for all buffers empty.
950 config PL310_ERRATA_769419
951 bool "PL310 errata: no automatic Store Buffer drain"
953 On revisions of the PL310 prior to r3p2, the Store Buffer does
954 not automatically drain. This can cause normal, non-cacheable
955 writes to be retained when the memory system is idle, leading
956 to suboptimal I/O performance for drivers using coherent DMA.
957 This option adds a write barrier to the cpu_idle loop so that,
958 on systems with an outer cache, the store buffer is drained
964 bool "Enable the Tauros2 L2 cache controller"
965 depends on (ARCH_DOVE || ARCH_MMP || CPU_PJ4)
969 This option enables the Tauros2 L2 cache controller (as
973 bool "Enable the L2 cache on XScale3"
978 This option enables the L2 cache on XScale3.
980 config ARM_L1_CACHE_SHIFT_6
984 Setting ARM L1 cache line size to 64 Bytes.
986 config ARM_L1_CACHE_SHIFT
988 default 6 if ARM_L1_CACHE_SHIFT_6
991 config ARM_DMA_MEM_BUFFERABLE
992 bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
993 depends on !(MACH_REALVIEW_PB1176 || REALVIEW_EB_ARM11MP || \
994 MACH_REALVIEW_PB11MP)
995 default y if CPU_V6 || CPU_V6K || CPU_V7
997 Historically, the kernel has used strongly ordered mappings to
998 provide DMA coherent memory. With the advent of ARMv7, mapping
999 memory with differing types results in unpredictable behaviour,
1000 so on these CPUs, this option is forced on.
1002 Multiple mappings with differing attributes is also unpredictable
1003 on ARMv6 CPUs, but since they do not have aggressive speculative
1004 prefetch, no harm appears to occur.
1006 However, drivers may be missing the necessary barriers for ARMv6,
1007 and therefore turning this on may result in unpredictable driver
1008 behaviour. Therefore, we offer this as an option.
1010 You are recommended say 'Y' here and debug any affected drivers.
1012 config ARCH_HAS_BARRIERS
1015 This option allows the use of custom mandatory barriers
1016 included via the mach/barriers.h file.
1018 config ARCH_SUPPORTS_BIG_ENDIAN
1021 This option specifies the architecture can support big endian
1024 config ARM_KERNMEM_PERMS
1025 bool "Restrict kernel memory permissions"
1028 If this is set, kernel memory other than kernel text (and rodata)
1029 will be made non-executable. The tradeoff is that each region is
1030 padded to section-size (1MiB) boundaries (because their permissions
1031 are different and splitting the 1M pages into 4K ones causes TLB
1032 performance problems), wasting memory.
1035 bool "Make kernel text and rodata read-only"
1036 depends on ARM_KERNMEM_PERMS
1039 If this is set, kernel text and rodata will be made read-only. This
1040 is to help catch accidental or malicious attempts to change the
1041 kernel's executable code. Additionally splits rodata from kernel
1042 text so it can be made explicitly non-executable. This creates
1043 another section-size padded region, so it can waste more memory
1044 space while gaining the read-only protections.