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
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.
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_SPECTRE if MMU
400 select CPU_TLB_V7 if MMU
406 select CPU_ABRT_NOMMU
408 select CPU_PABRT_LEGACY
413 # There are no CPUs available with MMU that don't implement an ARM ISA:
416 Select this if your CPU doesn't support the 32 bit ARM instructions.
418 # Figure out what processor architecture version we should be using.
419 # This defines the compiler instruction set which depends on the machine type.
422 select CPU_USE_DOMAINS if MMU
423 select NEED_KUSER_HELPERS
424 select TLS_REG_EMUL if SMP || !MMU
428 select CPU_USE_DOMAINS if MMU
429 select NEED_KUSER_HELPERS
430 select TLS_REG_EMUL if SMP || !MMU
434 select CPU_USE_DOMAINS if MMU
435 select NEED_KUSER_HELPERS
436 select TLS_REG_EMUL if SMP || !MMU
440 select CPU_USE_DOMAINS if MMU
441 select NEED_KUSER_HELPERS
442 select TLS_REG_EMUL if SMP || !MMU
446 select TLS_REG_EMUL if !CPU_32v6K && !MMU
458 config CPU_ABRT_NOMMU
473 config CPU_ABRT_EV5TJ
482 config CPU_PABRT_LEGACY
495 config CPU_CACHE_V4WT
498 config CPU_CACHE_V4WB
510 config CPU_CACHE_VIVT
513 config CPU_CACHE_VIPT
520 # The copy-page model
527 config CPU_COPY_FEROCEON
536 # This selects the TLB model
540 ARM Architecture Version 4 TLB with writethrough cache.
545 ARM Architecture Version 4 TLB with writeback cache.
550 ARM Architecture Version 4 TLB with writeback cache and invalidate
551 instruction cache entry.
553 config CPU_TLB_FEROCEON
556 Feroceon TLB (v4wbi with non-outer-cachable page table walks).
561 Faraday ARM FA526 architecture, unified TLB with writeback cache
562 and invalidate instruction cache entry. Branch target buffer is
571 config VERIFY_PERMISSION_FAULT
578 This indicates whether the CPU has the ASID register; used to
579 tag TLB and possibly cache entries.
584 Processor has the CP15 register.
590 Processor has the CP15 register, which has MMU related registers.
596 Processor has the CP15 register, which has MPU related registers.
598 config CPU_USE_DOMAINS
601 This option enables or disables the use of domain switching
602 via the set_fs() function.
604 config CPU_V7M_NUM_IRQ
605 int "Number of external interrupts connected to the NVIC"
607 default 90 if ARCH_STM32
608 default 38 if ARCH_EFM32
609 default 112 if SOC_VF610
612 This option indicates the number of interrupts connected to the NVIC.
613 The value can be larger than the real number of interrupts supported
614 by the system, but must not be lower.
615 The default value is 240, corresponding to the maximum number of
616 interrupts supported by the NVIC on Cortex-M family.
618 If unsure, keep default value.
621 # CPU supports 36-bit I/O
626 comment "Processor Features"
629 bool "Support for the Large Physical Address Extension"
630 depends on MMU && CPU_32v7 && !CPU_32v6 && !CPU_32v5 && \
631 !CPU_32v4 && !CPU_32v3
633 Say Y if you have an ARMv7 processor supporting the LPAE page
634 table format and you would like to access memory beyond the
635 4GB limit. The resulting kernel image will not run on
636 processors without the LPA extension.
642 depends on ARM_LPAE && ARM_PATCH_PHYS_VIRT && ARCH_KEYSTONE
644 config ARCH_PHYS_ADDR_T_64BIT
647 config ARCH_DMA_ADDR_T_64BIT
651 bool "Support Thumb user binaries" if !CPU_THUMBONLY
652 depends on CPU_ARM720T || CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || \
653 CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || \
654 CPU_ARM1020 || CPU_ARM1020E || CPU_ARM1022 || CPU_ARM1026 || \
655 CPU_XSCALE || CPU_XSC3 || CPU_MOHAWK || CPU_V6 || CPU_V6K || \
656 CPU_V7 || CPU_FEROCEON || CPU_V7M
659 Say Y if you want to include kernel support for running user space
662 The Thumb instruction set is a compressed form of the standard ARM
663 instruction set resulting in smaller binaries at the expense of
664 slightly less efficient code.
666 If you don't know what this all is, saying Y is a safe choice.
669 bool "Enable ThumbEE CPU extension"
672 Say Y here if you have a CPU with the ThumbEE extension and code to
673 make use of it. Say N for code that can run on CPUs without ThumbEE.
680 Enable the kernel to make use of the ARM Virtualization
681 Extensions to install hypervisors without run-time firmware
684 A compliant bootloader is required in order to make maximum
685 use of this feature. Refer to Documentation/arm/Booting for
689 bool "Emulate SWP/SWPB instructions" if !SMP
692 select HAVE_PROC_CPU if PROC_FS
694 ARMv6 architecture deprecates use of the SWP/SWPB instructions.
695 ARMv7 multiprocessing extensions introduce the ability to disable
696 these instructions, triggering an undefined instruction exception
697 when executed. Say Y here to enable software emulation of these
698 instructions for userspace (not kernel) using LDREX/STREX.
699 Also creates /proc/cpu/swp_emulation for statistics.
701 In some older versions of glibc [<=2.8] SWP is used during futex
702 trylock() operations with the assumption that the code will not
703 be preempted. This invalid assumption may be more likely to fail
704 with SWP emulation enabled, leading to deadlock of the user
707 NOTE: when accessing uncached shared regions, LDREX/STREX rely
708 on an external transaction monitoring block called a global
709 monitor to maintain update atomicity. If your system does not
710 implement a global monitor, this option can cause programs that
711 perform SWP operations to uncached memory to deadlock.
715 config CPU_BIG_ENDIAN
716 bool "Build big-endian kernel"
717 depends on ARCH_SUPPORTS_BIG_ENDIAN
719 Say Y if you plan on running a kernel in big-endian mode.
720 Note that your board must be properly built and your board
721 port must properly enable any big-endian related features
722 of your chipset/board/processor.
724 config CPU_ENDIAN_BE8
726 depends on CPU_BIG_ENDIAN
727 default CPU_V6 || CPU_V6K || CPU_V7
729 Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.
731 config CPU_ENDIAN_BE32
733 depends on CPU_BIG_ENDIAN
734 default !CPU_ENDIAN_BE8
736 Support for the BE-32 (big-endian) mode on pre-ARMv6 processors.
738 config CPU_HIGH_VECTOR
739 depends on !MMU && CPU_CP15 && !CPU_ARM740T
740 bool "Select the High exception vector"
742 Say Y here to select high exception vector(0xFFFF0000~).
743 The exception vector can vary depending on the platform
744 design in nommu mode. If your platform needs to select
745 high exception vector, say Y.
746 Otherwise or if you are unsure, say N, and the low exception
747 vector (0x00000000~) will be used.
749 config CPU_ICACHE_DISABLE
750 bool "Disable I-Cache (I-bit)"
751 depends on CPU_CP15 && !(CPU_ARM720T || CPU_ARM740T || CPU_XSCALE || CPU_XSC3)
753 Say Y here to disable the processor instruction cache. Unless
754 you have a reason not to or are unsure, say N.
756 config CPU_DCACHE_DISABLE
757 bool "Disable D-Cache (C-bit)"
758 depends on CPU_CP15 && !SMP
760 Say Y here to disable the processor data cache. Unless
761 you have a reason not to or are unsure, say N.
763 config CPU_DCACHE_SIZE
765 depends on CPU_ARM740T || CPU_ARM946E
766 default 0x00001000 if CPU_ARM740T
767 default 0x00002000 # default size for ARM946E-S
769 Some cores are synthesizable to have various sized cache. For
770 ARM946E-S case, it can vary from 0KB to 1MB.
771 To support such cache operations, it is efficient to know the size
773 If your SoC is configured to have a different size, define the value
774 here with proper conditions.
776 config CPU_DCACHE_WRITETHROUGH
777 bool "Force write through D-cache"
778 depends on (CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || CPU_ARM1020 || CPU_FA526) && !CPU_DCACHE_DISABLE
779 default y if CPU_ARM925T
781 Say Y here to use the data cache in writethrough mode. Unless you
782 specifically require this or are unsure, say N.
784 config CPU_CACHE_ROUND_ROBIN
785 bool "Round robin I and D cache replacement algorithm"
786 depends on (CPU_ARM926T || CPU_ARM946E || CPU_ARM1020) && (!CPU_ICACHE_DISABLE || !CPU_DCACHE_DISABLE)
788 Say Y here to use the predictable round-robin cache replacement
789 policy. Unless you specifically require this or are unsure, say N.
791 config CPU_BPREDICT_DISABLE
792 bool "Disable branch prediction"
793 depends on CPU_ARM1020 || CPU_V6 || CPU_V6K || CPU_MOHAWK || CPU_XSC3 || CPU_V7 || CPU_FA526
795 Say Y here to disable branch prediction. If unsure, say N.
800 config HARDEN_BRANCH_PREDICTOR
801 bool "Harden the branch predictor against aliasing attacks" if EXPERT
802 depends on CPU_SPECTRE
805 Speculation attacks against some high-performance processors rely
806 on being able to manipulate the branch predictor for a victim
807 context by executing aliasing branches in the attacker context.
808 Such attacks can be partially mitigated against by clearing
809 internal branch predictor state and limiting the prediction
810 logic in some situations.
812 This config option will take CPU-specific actions to harden
813 the branch predictor against aliasing attacks and may rely on
814 specific instruction sequences or control bits being set by
821 select NEED_KUSER_HELPERS
823 An SMP system using a pre-ARMv6 processor (there are apparently
824 a few prototypes like that in existence) and therefore access to
825 that required register must be emulated.
827 config NEED_KUSER_HELPERS
831 bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
835 Warning: disabling this option may break user programs.
837 Provide kuser helpers in the vector page. The kernel provides
838 helper code to userspace in read only form at a fixed location
839 in the high vector page to allow userspace to be independent of
840 the CPU type fitted to the system. This permits binaries to be
841 run on ARMv4 through to ARMv7 without modification.
843 See Documentation/arm/kernel_user_helpers.txt for details.
845 However, the fixed address nature of these helpers can be used
846 by ROP (return orientated programming) authors when creating
849 If all of the binaries and libraries which run on your platform
850 are built specifically for your platform, and make no use of
851 these helpers, then you can turn this option off to hinder
852 such exploits. However, in that case, if a binary or library
853 relying on those helpers is run, it will receive a SIGILL signal,
854 which will terminate the program.
856 Say N here only if you are absolutely certain that you do not
857 need these helpers; otherwise, the safe option is to say Y.
860 bool "Enable VDSO for acceleration of some system calls"
861 depends on AEABI && MMU && CPU_V7
862 default y if ARM_ARCH_TIMER
863 select GENERIC_TIME_VSYSCALL
865 Place in the process address space an ELF shared object
866 providing fast implementations of gettimeofday and
867 clock_gettime. Systems that implement the ARM architected
868 timer will receive maximum benefit.
870 You must have glibc 2.22 or later for programs to seamlessly
871 take advantage of this.
873 config DMA_CACHE_RWFO
874 bool "Enable read/write for ownership DMA cache maintenance"
875 depends on CPU_V6K && SMP
878 The Snoop Control Unit on ARM11MPCore does not detect the
879 cache maintenance operations and the dma_{map,unmap}_area()
880 functions may leave stale cache entries on other CPUs. By
881 enabling this option, Read or Write For Ownership in the ARMv6
882 DMA cache maintenance functions is performed. These LDR/STR
883 instructions change the cache line state to shared or modified
884 so that the cache operation has the desired effect.
886 Note that the workaround is only valid on processors that do
887 not perform speculative loads into the D-cache. For such
888 processors, if cache maintenance operations are not broadcast
889 in hardware, other workarounds are needed (e.g. cache
890 maintenance broadcasting in software via FIQ).
895 config OUTER_CACHE_SYNC
899 The outer cache has a outer_cache_fns.sync function pointer
900 that can be used to drain the write buffer of the outer cache.
902 config CACHE_FEROCEON_L2
903 bool "Enable the Feroceon L2 cache controller"
904 depends on ARCH_MV78XX0 || ARCH_MVEBU
908 This option enables the Feroceon L2 cache controller.
910 config CACHE_FEROCEON_L2_WRITETHROUGH
911 bool "Force Feroceon L2 cache write through"
912 depends on CACHE_FEROCEON_L2
914 Say Y here to use the Feroceon L2 cache in writethrough mode.
915 Unless you specifically require this, say N for writeback mode.
917 config MIGHT_HAVE_CACHE_L2X0
920 This option should be selected by machines which have a L2x0
921 or PL310 cache controller, but where its use is optional.
923 The only effect of this option is to make CACHE_L2X0 and
924 related options available to the user for configuration.
926 Boards or SoCs which always require the cache controller
927 support to be present should select CACHE_L2X0 directly
928 instead of this option, thus preventing the user from
929 inadvertently configuring a broken kernel.
932 bool "Enable the L2x0 outer cache controller" if MIGHT_HAVE_CACHE_L2X0
933 default MIGHT_HAVE_CACHE_L2X0
935 select OUTER_CACHE_SYNC
937 This option enables the L2x0 PrimeCell.
941 config PL310_ERRATA_588369
942 bool "PL310 errata: Clean & Invalidate maintenance operations do not invalidate clean lines"
944 The PL310 L2 cache controller implements three types of Clean &
945 Invalidate maintenance operations: by Physical Address
946 (offset 0x7F0), by Index/Way (0x7F8) and by Way (0x7FC).
947 They are architecturally defined to behave as the execution of a
948 clean operation followed immediately by an invalidate operation,
949 both performing to the same memory location. This functionality
950 is not correctly implemented in PL310 prior to r2p0 (fixed in r2p0)
951 as clean lines are not invalidated as a result of these operations.
953 config PL310_ERRATA_727915
954 bool "PL310 errata: Background Clean & Invalidate by Way operation can cause data corruption"
956 PL310 implements the Clean & Invalidate by Way L2 cache maintenance
957 operation (offset 0x7FC). This operation runs in background so that
958 PL310 can handle normal accesses while it is in progress. Under very
959 rare circumstances, due to this erratum, write data can be lost when
960 PL310 treats a cacheable write transaction during a Clean &
961 Invalidate by Way operation. Revisions prior to r3p1 are affected by
962 this errata (fixed in r3p1).
964 config PL310_ERRATA_753970
965 bool "PL310 errata: cache sync operation may be faulty"
967 This option enables the workaround for the 753970 PL310 (r3p0) erratum.
969 Under some condition the effect of cache sync operation on
970 the store buffer still remains when the operation completes.
971 This means that the store buffer is always asked to drain and
972 this prevents it from merging any further writes. The workaround
973 is to replace the normal offset of cache sync operation (0x730)
974 by another offset targeting an unmapped PL310 register 0x740.
975 This has the same effect as the cache sync operation: store buffer
976 drain and waiting for all buffers empty.
978 config PL310_ERRATA_769419
979 bool "PL310 errata: no automatic Store Buffer drain"
981 On revisions of the PL310 prior to r3p2, the Store Buffer does
982 not automatically drain. This can cause normal, non-cacheable
983 writes to be retained when the memory system is idle, leading
984 to suboptimal I/O performance for drivers using coherent DMA.
985 This option adds a write barrier to the cpu_idle loop so that,
986 on systems with an outer cache, the store buffer is drained
992 bool "Enable the Tauros2 L2 cache controller"
993 depends on (ARCH_DOVE || ARCH_MMP || CPU_PJ4)
997 This option enables the Tauros2 L2 cache controller (as
1000 config CACHE_UNIPHIER
1001 bool "Enable the UniPhier outer cache controller"
1002 depends on ARCH_UNIPHIER
1005 select OUTER_CACHE_SYNC
1007 This option enables the UniPhier outer cache (system cache)
1011 bool "Enable the L2 cache on XScale3"
1016 This option enables the L2 cache on XScale3.
1018 config ARM_L1_CACHE_SHIFT_6
1022 Setting ARM L1 cache line size to 64 Bytes.
1024 config ARM_L1_CACHE_SHIFT
1026 default 6 if ARM_L1_CACHE_SHIFT_6
1029 config ARM_DMA_MEM_BUFFERABLE
1030 bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K) && !CPU_V7
1031 depends on !(MACH_REALVIEW_PB1176 || REALVIEW_EB_ARM11MP || \
1032 MACH_REALVIEW_PB11MP)
1033 default y if CPU_V6 || CPU_V6K || CPU_V7
1035 Historically, the kernel has used strongly ordered mappings to
1036 provide DMA coherent memory. With the advent of ARMv7, mapping
1037 memory with differing types results in unpredictable behaviour,
1038 so on these CPUs, this option is forced on.
1040 Multiple mappings with differing attributes is also unpredictable
1041 on ARMv6 CPUs, but since they do not have aggressive speculative
1042 prefetch, no harm appears to occur.
1044 However, drivers may be missing the necessary barriers for ARMv6,
1045 and therefore turning this on may result in unpredictable driver
1046 behaviour. Therefore, we offer this as an option.
1048 You are recommended say 'Y' here and debug any affected drivers.
1050 config ARCH_HAS_BARRIERS
1053 This option allows the use of custom mandatory barriers
1054 included via the mach/barriers.h file.
1059 config ARCH_SUPPORTS_BIG_ENDIAN
1062 This option specifies the architecture can support big endian
1065 config ARM_KERNMEM_PERMS
1066 bool "Restrict kernel memory permissions"
1069 If this is set, kernel memory other than kernel text (and rodata)
1070 will be made non-executable. The tradeoff is that each region is
1071 padded to section-size (1MiB) boundaries (because their permissions
1072 are different and splitting the 1M pages into 4K ones causes TLB
1073 performance problems), wasting memory.
1076 bool "Make kernel text and rodata read-only"
1077 depends on ARM_KERNMEM_PERMS
1080 If this is set, kernel text and rodata will be made read-only. This
1081 is to help catch accidental or malicious attempts to change the
1082 kernel's executable code. Additionally splits rodata from kernel
1083 text so it can be made explicitly non-executable. This creates
1084 another section-size padded region, so it can waste more memory
1085 space while gaining the read-only protections.