1 # SPDX-License-Identifier: GPL-2.0
2 comment "Processor Type"
4 # Select CPU types depending on the architecture selected. This selects
5 # which CPUs we support in the kernel image, and the compiler instruction
15 select CPU_PABRT_LEGACY
17 A 32-bit RISC microprocessor based on the ARM7 processor core
18 which has no memory control unit and cache.
20 Say Y if you want support for the ARM7TDMI processor.
30 select CPU_COPY_V4WT if MMU
32 select CPU_PABRT_LEGACY
33 select CPU_THUMB_CAPABLE
34 select CPU_TLB_V4WT if MMU
36 A 32-bit RISC processor with 8kByte Cache, Write Buffer and
37 MMU built around an ARM7TDMI core.
39 Say Y if you want support for the ARM720T processor.
50 select CPU_PABRT_LEGACY
51 select CPU_THUMB_CAPABLE
53 A 32-bit RISC processor with 8KB cache or 4KB variants,
54 write buffer and MPU(Protection Unit) built around
57 Say Y if you want support for the ARM740T processor.
67 select CPU_PABRT_LEGACY
69 A 32-bit RISC microprocessor based on the ARM9 processor core
70 which has no memory control unit and cache.
72 Say Y if you want support for the ARM9TDMI processor.
82 select CPU_COPY_V4WB if MMU
84 select CPU_PABRT_LEGACY
85 select CPU_THUMB_CAPABLE
86 select CPU_TLB_V4WBI if MMU
88 The ARM920T is licensed to be produced by numerous vendors,
89 and is used in the Cirrus EP93xx and the Samsung S3C2410.
91 Say Y if you want support for the ARM920T processor.
100 select CPU_CACHE_VIVT
101 select CPU_COPY_V4WB if MMU
103 select CPU_PABRT_LEGACY
104 select CPU_THUMB_CAPABLE
105 select CPU_TLB_V4WBI if MMU
107 The ARM922T is a version of the ARM920T, but with smaller
108 instruction and data caches. It is used in Altera's
109 Excalibur XA device family and the ARM Integrator.
111 Say Y if you want support for the ARM922T processor.
119 select CPU_CACHE_V4WT
120 select CPU_CACHE_VIVT
121 select CPU_COPY_V4WB if MMU
123 select CPU_PABRT_LEGACY
124 select CPU_THUMB_CAPABLE
125 select CPU_TLB_V4WBI if MMU
127 The ARM925T is a mix between the ARM920T and ARM926T, but with
128 different instruction and data caches. It is used in TI's OMAP
131 Say Y if you want support for the ARM925T processor.
138 select CPU_ABRT_EV5TJ
139 select CPU_CACHE_VIVT
140 select CPU_COPY_V4WB if MMU
142 select CPU_PABRT_LEGACY
143 select CPU_THUMB_CAPABLE
144 select CPU_TLB_V4WBI if MMU
146 This is a variant of the ARM920. It has slightly different
147 instruction sequences for cache and TLB operations. Curiously,
148 there is no documentation on it at the ARM corporate website.
150 Say Y if you want support for the ARM926T processor.
159 select CPU_CACHE_VIVT
160 select CPU_COPY_FA if MMU
162 select CPU_PABRT_LEGACY
163 select CPU_TLB_FA if MMU
165 The FA526 is a version of the ARMv4 compatible processor with
166 Branch Target Buffer, Unified TLB and cache line size 16.
168 Say Y if you want support for the FA526 processor.
176 select CPU_ABRT_NOMMU
177 select CPU_CACHE_VIVT
179 select CPU_PABRT_LEGACY
180 select CPU_THUMB_CAPABLE
182 ARM940T is a member of the ARM9TDMI family of general-
183 purpose microprocessors with MPU and separate 4KB
184 instruction and 4KB data cases, each with a 4-word line
187 Say Y if you want support for the ARM940T processor.
195 select CPU_ABRT_NOMMU
196 select CPU_CACHE_VIVT
198 select CPU_PABRT_LEGACY
199 select CPU_THUMB_CAPABLE
201 ARM946E-S is a member of the ARM9E-S family of high-
202 performance, 32-bit system-on-chip processor solutions.
203 The TCM and ARMv5TE 32-bit instruction set is supported.
205 Say Y if you want support for the ARM946E-S processor.
208 # ARM1020 - needs validating
213 select CPU_CACHE_V4WT
214 select CPU_CACHE_VIVT
215 select CPU_COPY_V4WB if MMU
217 select CPU_PABRT_LEGACY
218 select CPU_THUMB_CAPABLE
219 select CPU_TLB_V4WBI if MMU
221 The ARM1020 is the 32K cached version of the ARM10 processor,
222 with an addition of a floating-point unit.
224 Say Y if you want support for the ARM1020 processor.
227 # ARM1020E - needs validating
233 select CPU_CACHE_V4WT
234 select CPU_CACHE_VIVT
235 select CPU_COPY_V4WB if MMU
237 select CPU_PABRT_LEGACY
238 select CPU_THUMB_CAPABLE
239 select CPU_TLB_V4WBI if MMU
246 select CPU_CACHE_VIVT
247 select CPU_COPY_V4WB if MMU # can probably do better
249 select CPU_PABRT_LEGACY
250 select CPU_THUMB_CAPABLE
251 select CPU_TLB_V4WBI if MMU
253 The ARM1022E is an implementation of the ARMv5TE architecture
254 based upon the ARM10 integer core with a 16KiB L1 Harvard cache,
255 embedded trace macrocell, and a floating-point unit.
257 Say Y if you want support for the ARM1022E processor.
264 select CPU_ABRT_EV5T # But need Jazelle, but EV5TJ ignores bit 10
265 select CPU_CACHE_VIVT
266 select CPU_COPY_V4WB if MMU # can probably do better
268 select CPU_PABRT_LEGACY
269 select CPU_THUMB_CAPABLE
270 select CPU_TLB_V4WBI if MMU
272 The ARM1026EJ-S is an implementation of the ARMv5TEJ architecture
273 based upon the ARM10 integer core.
275 Say Y if you want support for the ARM1026EJ-S processor.
281 select CPU_32v3 if ARCH_RPC
282 select CPU_32v4 if !ARCH_RPC
284 select CPU_CACHE_V4WB
285 select CPU_CACHE_VIVT
286 select CPU_COPY_V4WB if MMU
288 select CPU_PABRT_LEGACY
289 select CPU_TLB_V4WB if MMU
291 The Intel StrongARM(R) SA-110 is a 32-bit microprocessor and
292 is available at five speeds ranging from 100 MHz to 233 MHz.
293 More information is available at
294 <http://developer.intel.com/design/strong/sa110.htm>.
296 Say Y if you want support for the SA-110 processor.
304 select CPU_CACHE_V4WB
305 select CPU_CACHE_VIVT
307 select CPU_PABRT_LEGACY
308 select CPU_TLB_V4WB if MMU
315 select CPU_CACHE_VIVT
317 select CPU_PABRT_LEGACY
318 select CPU_THUMB_CAPABLE
319 select CPU_TLB_V4WBI if MMU
321 # XScale Core Version 3
326 select CPU_CACHE_VIVT
328 select CPU_PABRT_LEGACY
329 select CPU_THUMB_CAPABLE
330 select CPU_TLB_V4WBI if MMU
333 # Marvell PJ1 (Mohawk)
338 select CPU_CACHE_VIVT
339 select CPU_COPY_V4WB if MMU
341 select CPU_PABRT_LEGACY
342 select CPU_THUMB_CAPABLE
343 select CPU_TLB_V4WBI if MMU
350 select CPU_CACHE_VIVT
351 select CPU_COPY_FEROCEON if MMU
353 select CPU_PABRT_LEGACY
354 select CPU_THUMB_CAPABLE
355 select CPU_TLB_FEROCEON if MMU
357 config CPU_FEROCEON_OLD_ID
358 bool "Accept early Feroceon cores with an ARM926 ID"
359 depends on CPU_FEROCEON && !CPU_ARM926T
362 This enables the usage of some old Feroceon cores
363 for which the CPU ID is equal to the ARM926 ID.
364 Relevant for Feroceon-1850 and early Feroceon-2850.
382 select CPU_CACHE_VIPT
383 select CPU_COPY_V6 if MMU
385 select CPU_HAS_ASID if MMU
387 select CPU_THUMB_CAPABLE
388 select CPU_TLB_V6 if MMU
389 select SMP_ON_UP if SMP
398 select CPU_CACHE_VIPT
399 select CPU_COPY_V6 if MMU
401 select CPU_HAS_ASID if MMU
403 select CPU_THUMB_CAPABLE
404 select CPU_TLB_V6 if MMU
413 select CPU_CACHE_VIPT
414 select CPU_COPY_V6 if MMU
415 select CPU_CP15_MMU if MMU
416 select CPU_CP15_MPU if !MMU
417 select CPU_HAS_ASID if MMU
419 select CPU_SPECTRE if MMU
420 select CPU_THUMB_CAPABLE
421 select CPU_TLB_V7 if MMU
427 select CPU_ABRT_NOMMU
430 select CPU_PABRT_LEGACY
435 select CPU_THUMB_CAPABLE
436 # There are no CPUs available with MMU that don't implement an ARM ISA:
439 Select this if your CPU doesn't support the 32 bit ARM instructions.
441 config CPU_THUMB_CAPABLE
444 Select this if your CPU can support Thumb mode.
446 # Figure out what processor architecture version we should be using.
447 # This defines the compiler instruction set which depends on the machine type.
450 select CPU_USE_DOMAINS if MMU
451 select NEED_KUSER_HELPERS
452 select TLS_REG_EMUL if SMP || !MMU
453 select CPU_NO_EFFICIENT_FFS
457 select CPU_USE_DOMAINS if MMU
458 select NEED_KUSER_HELPERS
459 select TLS_REG_EMUL if SMP || !MMU
460 select CPU_NO_EFFICIENT_FFS
464 select CPU_USE_DOMAINS if MMU
465 select NEED_KUSER_HELPERS
466 select TLS_REG_EMUL if SMP || !MMU
467 select CPU_NO_EFFICIENT_FFS
471 select CPU_USE_DOMAINS if MMU
472 select NEED_KUSER_HELPERS
473 select TLS_REG_EMUL if SMP || !MMU
477 select TLS_REG_EMUL if !CPU_32v6K && !MMU
489 config CPU_ABRT_NOMMU
504 config CPU_ABRT_EV5TJ
513 config CPU_PABRT_LEGACY
526 config CPU_CACHE_V4WT
529 config CPU_CACHE_V4WB
541 config CPU_CACHE_VIVT
544 config CPU_CACHE_VIPT
554 # The copy-page model
561 config CPU_COPY_FEROCEON
570 # This selects the TLB model
574 ARM Architecture Version 4 TLB with writethrough cache.
579 ARM Architecture Version 4 TLB with writeback cache.
584 ARM Architecture Version 4 TLB with writeback cache and invalidate
585 instruction cache entry.
587 config CPU_TLB_FEROCEON
590 Feroceon TLB (v4wbi with non-outer-cachable page table walks).
595 Faraday ARM FA526 architecture, unified TLB with writeback cache
596 and invalidate instruction cache entry. Branch target buffer is
610 This indicates whether the CPU has the ASID register; used to
611 tag TLB and possibly cache entries.
616 Processor has the CP15 register.
622 Processor has the CP15 register, which has MMU related registers.
628 Processor has the CP15 register, which has MPU related registers.
630 config CPU_USE_DOMAINS
633 This option enables or disables the use of domain switching
634 via the set_fs() function.
636 config CPU_V7M_NUM_IRQ
637 int "Number of external interrupts connected to the NVIC"
639 default 90 if ARCH_STM32
640 default 112 if SOC_VF610
643 This option indicates the number of interrupts connected to the NVIC.
644 The value can be larger than the real number of interrupts supported
645 by the system, but must not be lower.
646 The default value is 240, corresponding to the maximum number of
647 interrupts supported by the NVIC on Cortex-M family.
649 If unsure, keep default value.
652 # CPU supports 36-bit I/O
657 comment "Processor Features"
660 bool "Support for the Large Physical Address Extension"
661 depends on MMU && CPU_32v7 && !CPU_32v6 && !CPU_32v5 && \
662 !CPU_32v4 && !CPU_32v3
663 select PHYS_ADDR_T_64BIT
666 Say Y if you have an ARMv7 processor supporting the LPAE page
667 table format and you would like to access memory beyond the
668 4GB limit. The resulting kernel image will not run on
669 processors without the LPA extension.
675 depends on ARM_LPAE && ARM_PATCH_PHYS_VIRT && ARCH_KEYSTONE
678 bool "Support Thumb user binaries" if !CPU_THUMBONLY && EXPERT
679 depends on CPU_THUMB_CAPABLE && !CPU_32v4
682 Say Y if you want to include kernel support for running user space
685 The Thumb instruction set is a compressed form of the standard ARM
686 instruction set resulting in smaller binaries at the expense of
687 slightly less efficient code.
689 If this option is disabled, and you run userspace that switches to
690 Thumb mode, signal handling will not work correctly, resulting in
691 segmentation faults or illegal instruction aborts.
693 If you don't know what this all is, saying Y is a safe choice.
696 bool "Enable ThumbEE CPU extension"
699 Say Y here if you have a CPU with the ThumbEE extension and code to
700 make use of it. Say N for code that can run on CPUs without ThumbEE.
706 Enable the kernel to make use of the ARM Virtualization
707 Extensions to install hypervisors without run-time firmware
710 A compliant bootloader is required in order to make maximum
711 use of this feature. Refer to Documentation/arm/booting.rst for
715 bool "Emulate SWP/SWPB instructions" if !SMP
718 select HAVE_PROC_CPU if PROC_FS
720 ARMv6 architecture deprecates use of the SWP/SWPB instructions.
721 ARMv7 multiprocessing extensions introduce the ability to disable
722 these instructions, triggering an undefined instruction exception
723 when executed. Say Y here to enable software emulation of these
724 instructions for userspace (not kernel) using LDREX/STREX.
725 Also creates /proc/cpu/swp_emulation for statistics.
727 In some older versions of glibc [<=2.8] SWP is used during futex
728 trylock() operations with the assumption that the code will not
729 be preempted. This invalid assumption may be more likely to fail
730 with SWP emulation enabled, leading to deadlock of the user
733 NOTE: when accessing uncached shared regions, LDREX/STREX rely
734 on an external transaction monitoring block called a global
735 monitor to maintain update atomicity. If your system does not
736 implement a global monitor, this option can cause programs that
737 perform SWP operations to uncached memory to deadlock.
741 config CPU_BIG_ENDIAN
742 bool "Build big-endian kernel"
743 depends on ARCH_SUPPORTS_BIG_ENDIAN
744 depends on !LD_IS_LLD
746 Say Y if you plan on running a kernel in big-endian mode.
747 Note that your board must be properly built and your board
748 port must properly enable any big-endian related features
749 of your chipset/board/processor.
751 config CPU_ENDIAN_BE8
753 depends on CPU_BIG_ENDIAN
754 default CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M
756 Support for the BE-8 (big-endian) mode on ARMv6 and ARMv7 processors.
758 config CPU_ENDIAN_BE32
760 depends on CPU_BIG_ENDIAN
761 default !CPU_ENDIAN_BE8
763 Support for the BE-32 (big-endian) mode on pre-ARMv6 processors.
765 config CPU_HIGH_VECTOR
766 depends on !MMU && CPU_CP15 && !CPU_ARM740T
767 bool "Select the High exception vector"
769 Say Y here to select high exception vector(0xFFFF0000~).
770 The exception vector can vary depending on the platform
771 design in nommu mode. If your platform needs to select
772 high exception vector, say Y.
773 Otherwise or if you are unsure, say N, and the low exception
774 vector (0x00000000~) will be used.
776 config CPU_ICACHE_DISABLE
777 bool "Disable I-Cache (I-bit)"
778 depends on (CPU_CP15 && !(CPU_ARM720T || CPU_ARM740T || CPU_XSCALE || CPU_XSC3)) || CPU_V7M
780 Say Y here to disable the processor instruction cache. Unless
781 you have a reason not to or are unsure, say N.
783 config CPU_ICACHE_MISMATCH_WORKAROUND
784 bool "Workaround for I-Cache line size mismatch between CPU cores"
785 depends on SMP && CPU_V7
787 Some big.LITTLE systems have I-Cache line size mismatch between
788 LITTLE and big cores. Say Y here to enable a workaround for
789 proper I-Cache support on such systems. If unsure, say N.
791 config CPU_DCACHE_DISABLE
792 bool "Disable D-Cache (C-bit)"
793 depends on (CPU_CP15 && !SMP) || CPU_V7M
795 Say Y here to disable the processor data cache. Unless
796 you have a reason not to or are unsure, say N.
798 config CPU_DCACHE_SIZE
800 depends on CPU_ARM740T || CPU_ARM946E
801 default 0x00001000 if CPU_ARM740T
802 default 0x00002000 # default size for ARM946E-S
804 Some cores are synthesizable to have various sized cache. For
805 ARM946E-S case, it can vary from 0KB to 1MB.
806 To support such cache operations, it is efficient to know the size
808 If your SoC is configured to have a different size, define the value
809 here with proper conditions.
811 config CPU_DCACHE_WRITETHROUGH
812 bool "Force write through D-cache"
813 depends on (CPU_ARM740T || CPU_ARM920T || CPU_ARM922T || CPU_ARM925T || CPU_ARM926T || CPU_ARM940T || CPU_ARM946E || CPU_ARM1020 || CPU_FA526) && !CPU_DCACHE_DISABLE
814 default y if CPU_ARM925T
816 Say Y here to use the data cache in writethrough mode. Unless you
817 specifically require this or are unsure, say N.
819 config CPU_CACHE_ROUND_ROBIN
820 bool "Round robin I and D cache replacement algorithm"
821 depends on (CPU_ARM926T || CPU_ARM946E || CPU_ARM1020) && (!CPU_ICACHE_DISABLE || !CPU_DCACHE_DISABLE)
823 Say Y here to use the predictable round-robin cache replacement
824 policy. Unless you specifically require this or are unsure, say N.
826 config CPU_BPREDICT_DISABLE
827 bool "Disable branch prediction"
828 depends on CPU_ARM1020 || CPU_V6 || CPU_V6K || CPU_MOHAWK || CPU_XSC3 || CPU_V7 || CPU_FA526 || CPU_V7M
830 Say Y here to disable branch prediction. If unsure, say N.
834 select GENERIC_CPU_VULNERABILITIES
836 config HARDEN_BRANCH_PREDICTOR
837 bool "Harden the branch predictor against aliasing attacks" if EXPERT
838 depends on CPU_SPECTRE
841 Speculation attacks against some high-performance processors rely
842 on being able to manipulate the branch predictor for a victim
843 context by executing aliasing branches in the attacker context.
844 Such attacks can be partially mitigated against by clearing
845 internal branch predictor state and limiting the prediction
846 logic in some situations.
848 This config option will take CPU-specific actions to harden
849 the branch predictor against aliasing attacks and may rely on
850 specific instruction sequences or control bits being set by
855 config HARDEN_BRANCH_HISTORY
856 bool "Harden Spectre style attacks against branch history" if EXPERT
857 depends on CPU_SPECTRE
860 Speculation attacks against some high-performance processors can
861 make use of branch history to influence future speculation. When
862 taking an exception, a sequence of branches overwrites the branch
863 history, or branch history is invalidated.
867 select NEED_KUSER_HELPERS
869 An SMP system using a pre-ARMv6 processor (there are apparently
870 a few prototypes like that in existence) and therefore access to
871 that required register must be emulated.
873 config NEED_KUSER_HELPERS
877 bool "Enable kuser helpers in vector page" if !NEED_KUSER_HELPERS
881 Warning: disabling this option may break user programs.
883 Provide kuser helpers in the vector page. The kernel provides
884 helper code to userspace in read only form at a fixed location
885 in the high vector page to allow userspace to be independent of
886 the CPU type fitted to the system. This permits binaries to be
887 run on ARMv4 through to ARMv7 without modification.
889 See Documentation/arm/kernel_user_helpers.rst for details.
891 However, the fixed address nature of these helpers can be used
892 by ROP (return orientated programming) authors when creating
895 If all of the binaries and libraries which run on your platform
896 are built specifically for your platform, and make no use of
897 these helpers, then you can turn this option off to hinder
898 such exploits. However, in that case, if a binary or library
899 relying on those helpers is run, it will receive a SIGILL signal,
900 which will terminate the program.
902 Say N here only if you are absolutely certain that you do not
903 need these helpers; otherwise, the safe option is to say Y.
906 bool "Enable VDSO for acceleration of some system calls"
907 depends on AEABI && MMU && CPU_V7
908 default y if ARM_ARCH_TIMER
909 select HAVE_GENERIC_VDSO
910 select GENERIC_TIME_VSYSCALL
911 select GENERIC_VDSO_32
912 select GENERIC_GETTIMEOFDAY
914 Place in the process address space an ELF shared object
915 providing fast implementations of gettimeofday and
916 clock_gettime. Systems that implement the ARM architected
917 timer will receive maximum benefit.
919 You must have glibc 2.22 or later for programs to seamlessly
920 take advantage of this.
922 config DMA_CACHE_RWFO
923 bool "Enable read/write for ownership DMA cache maintenance"
924 depends on CPU_V6K && SMP
927 The Snoop Control Unit on ARM11MPCore does not detect the
928 cache maintenance operations and the dma_{map,unmap}_area()
929 functions may leave stale cache entries on other CPUs. By
930 enabling this option, Read or Write For Ownership in the ARMv6
931 DMA cache maintenance functions is performed. These LDR/STR
932 instructions change the cache line state to shared or modified
933 so that the cache operation has the desired effect.
935 Note that the workaround is only valid on processors that do
936 not perform speculative loads into the D-cache. For such
937 processors, if cache maintenance operations are not broadcast
938 in hardware, other workarounds are needed (e.g. cache
939 maintenance broadcasting in software via FIQ).
944 config OUTER_CACHE_SYNC
948 The outer cache has a outer_cache_fns.sync function pointer
949 that can be used to drain the write buffer of the outer cache.
952 bool "Enable the Broadcom Brahma-B15 read-ahead cache controller"
953 depends on ARCH_BRCMSTB
956 This option enables the Broadcom Brahma-B15 read-ahead cache
957 controller. If disabled, the read-ahead cache remains off.
959 config CACHE_FEROCEON_L2
960 bool "Enable the Feroceon L2 cache controller"
961 depends on ARCH_MV78XX0 || ARCH_MVEBU
965 This option enables the Feroceon L2 cache controller.
967 config CACHE_FEROCEON_L2_WRITETHROUGH
968 bool "Force Feroceon L2 cache write through"
969 depends on CACHE_FEROCEON_L2
971 Say Y here to use the Feroceon L2 cache in writethrough mode.
972 Unless you specifically require this, say N for writeback mode.
974 config MIGHT_HAVE_CACHE_L2X0
977 This option should be selected by machines which have a L2x0
978 or PL310 cache controller, but where its use is optional.
980 The only effect of this option is to make CACHE_L2X0 and
981 related options available to the user for configuration.
983 Boards or SoCs which always require the cache controller
984 support to be present should select CACHE_L2X0 directly
985 instead of this option, thus preventing the user from
986 inadvertently configuring a broken kernel.
989 bool "Enable the L2x0 outer cache controller" if MIGHT_HAVE_CACHE_L2X0
990 default MIGHT_HAVE_CACHE_L2X0
992 select OUTER_CACHE_SYNC
994 This option enables the L2x0 PrimeCell.
996 config CACHE_L2X0_PMU
997 bool "L2x0 performance monitor support" if CACHE_L2X0
998 depends on PERF_EVENTS
1000 This option enables support for the performance monitoring features
1001 of the L220 and PL310 outer cache controllers.
1005 config PL310_ERRATA_588369
1006 bool "PL310 errata: Clean & Invalidate maintenance operations do not invalidate clean lines"
1008 The PL310 L2 cache controller implements three types of Clean &
1009 Invalidate maintenance operations: by Physical Address
1010 (offset 0x7F0), by Index/Way (0x7F8) and by Way (0x7FC).
1011 They are architecturally defined to behave as the execution of a
1012 clean operation followed immediately by an invalidate operation,
1013 both performing to the same memory location. This functionality
1014 is not correctly implemented in PL310 prior to r2p0 (fixed in r2p0)
1015 as clean lines are not invalidated as a result of these operations.
1017 config PL310_ERRATA_727915
1018 bool "PL310 errata: Background Clean & Invalidate by Way operation can cause data corruption"
1020 PL310 implements the Clean & Invalidate by Way L2 cache maintenance
1021 operation (offset 0x7FC). This operation runs in background so that
1022 PL310 can handle normal accesses while it is in progress. Under very
1023 rare circumstances, due to this erratum, write data can be lost when
1024 PL310 treats a cacheable write transaction during a Clean &
1025 Invalidate by Way operation. Revisions prior to r3p1 are affected by
1026 this errata (fixed in r3p1).
1028 config PL310_ERRATA_753970
1029 bool "PL310 errata: cache sync operation may be faulty"
1031 This option enables the workaround for the 753970 PL310 (r3p0) erratum.
1033 Under some condition the effect of cache sync operation on
1034 the store buffer still remains when the operation completes.
1035 This means that the store buffer is always asked to drain and
1036 this prevents it from merging any further writes. The workaround
1037 is to replace the normal offset of cache sync operation (0x730)
1038 by another offset targeting an unmapped PL310 register 0x740.
1039 This has the same effect as the cache sync operation: store buffer
1040 drain and waiting for all buffers empty.
1042 config PL310_ERRATA_769419
1043 bool "PL310 errata: no automatic Store Buffer drain"
1045 On revisions of the PL310 prior to r3p2, the Store Buffer does
1046 not automatically drain. This can cause normal, non-cacheable
1047 writes to be retained when the memory system is idle, leading
1048 to suboptimal I/O performance for drivers using coherent DMA.
1049 This option adds a write barrier to the cpu_idle loop so that,
1050 on systems with an outer cache, the store buffer is drained
1055 config CACHE_TAUROS2
1056 bool "Enable the Tauros2 L2 cache controller"
1057 depends on (CPU_MOHAWK || CPU_PJ4)
1061 This option enables the Tauros2 L2 cache controller (as
1064 config CACHE_UNIPHIER
1065 bool "Enable the UniPhier outer cache controller"
1066 depends on ARCH_UNIPHIER
1067 select ARM_L1_CACHE_SHIFT_7
1069 select OUTER_CACHE_SYNC
1071 This option enables the UniPhier outer cache (system cache)
1075 bool "Enable the L2 cache on XScale3"
1080 This option enables the L2 cache on XScale3.
1082 config ARM_L1_CACHE_SHIFT_6
1086 Setting ARM L1 cache line size to 64 Bytes.
1088 config ARM_L1_CACHE_SHIFT_7
1091 Setting ARM L1 cache line size to 128 Bytes.
1093 config ARM_L1_CACHE_SHIFT
1095 default 7 if ARM_L1_CACHE_SHIFT_7
1096 default 6 if ARM_L1_CACHE_SHIFT_6
1099 config ARM_DMA_MEM_BUFFERABLE
1100 bool "Use non-cacheable memory for DMA" if (CPU_V6 || CPU_V6K || CPU_V7M) && !CPU_V7
1101 default y if CPU_V6 || CPU_V6K || CPU_V7 || CPU_V7M
1103 Historically, the kernel has used strongly ordered mappings to
1104 provide DMA coherent memory. With the advent of ARMv7, mapping
1105 memory with differing types results in unpredictable behaviour,
1106 so on these CPUs, this option is forced on.
1108 Multiple mappings with differing attributes is also unpredictable
1109 on ARMv6 CPUs, but since they do not have aggressive speculative
1110 prefetch, no harm appears to occur.
1112 However, drivers may be missing the necessary barriers for ARMv6,
1113 and therefore turning this on may result in unpredictable driver
1114 behaviour. Therefore, we offer this as an option.
1116 On some of the beefier ARMv7-M machines (with DMA and write
1117 buffers) you likely want this enabled, while those that
1118 didn't need it until now also won't need it in the future.
1120 You are recommended say 'Y' here and debug any affected drivers.
1125 config ARCH_SUPPORTS_BIG_ENDIAN
1128 This option specifies the architecture can support big endian
1131 config DEBUG_ALIGN_RODATA
1132 bool "Make rodata strictly non-executable"
1133 depends on STRICT_KERNEL_RWX
1136 If this is set, rodata will be made explicitly non-executable. This
1137 provides protection on the rare chance that attackers might find and
1138 use ROP gadgets that exist in the rodata section. This adds an
1139 additional section-aligned split of rodata from kernel text so it
1140 can be made explicitly non-executable. This padding may waste memory
1141 space to gain the additional protection.