1# SPDX-License-Identifier: GPL-2.0 2config XTENSA 3 def_bool y 4 select ARCH_32BIT_OFF_T 5 select ARCH_HAS_BINFMT_FLAT if !MMU 6 select ARCH_HAS_DMA_PREP_COHERENT if MMU 7 select ARCH_HAS_SYNC_DMA_FOR_CPU if MMU 8 select ARCH_HAS_SYNC_DMA_FOR_DEVICE if MMU 9 select ARCH_HAS_DMA_SET_UNCACHED if MMU 10 select ARCH_USE_QUEUED_RWLOCKS 11 select ARCH_USE_QUEUED_SPINLOCKS 12 select ARCH_WANT_FRAME_POINTERS 13 select ARCH_WANT_IPC_PARSE_VERSION 14 select BUILDTIME_TABLE_SORT 15 select CLONE_BACKWARDS 16 select COMMON_CLK 17 select DMA_REMAP if MMU 18 select GENERIC_ATOMIC64 19 select GENERIC_CLOCKEVENTS 20 select GENERIC_IRQ_SHOW 21 select GENERIC_PCI_IOMAP 22 select GENERIC_SCHED_CLOCK 23 select GENERIC_STRNCPY_FROM_USER if KASAN 24 select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL 25 select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL 26 select HAVE_ARCH_TRACEHOOK 27 select HAVE_COPY_THREAD_TLS 28 select HAVE_DEBUG_KMEMLEAK 29 select HAVE_DMA_CONTIGUOUS 30 select HAVE_EXIT_THREAD 31 select HAVE_FUNCTION_TRACER 32 select HAVE_FUTEX_CMPXCHG if !MMU 33 select HAVE_HW_BREAKPOINT if PERF_EVENTS 34 select HAVE_IRQ_TIME_ACCOUNTING 35 select HAVE_OPROFILE 36 select HAVE_PCI 37 select HAVE_PERF_EVENTS 38 select HAVE_STACKPROTECTOR 39 select HAVE_SYSCALL_TRACEPOINTS 40 select IRQ_DOMAIN 41 select MODULES_USE_ELF_RELA 42 select PERF_USE_VMALLOC 43 select VIRT_TO_BUS 44 help 45 Xtensa processors are 32-bit RISC machines designed by Tensilica 46 primarily for embedded systems. These processors are both 47 configurable and extensible. The Linux port to the Xtensa 48 architecture supports all processor configurations and extensions, 49 with reasonable minimum requirements. The Xtensa Linux project has 50 a home page at <http://www.linux-xtensa.org/>. 51 52config GENERIC_HWEIGHT 53 def_bool y 54 55config ARCH_HAS_ILOG2_U32 56 def_bool n 57 58config ARCH_HAS_ILOG2_U64 59 def_bool n 60 61config NO_IOPORT_MAP 62 def_bool n 63 64config HZ 65 int 66 default 100 67 68config LOCKDEP_SUPPORT 69 def_bool y 70 71config STACKTRACE_SUPPORT 72 def_bool y 73 74config TRACE_IRQFLAGS_SUPPORT 75 def_bool y 76 77config MMU 78 def_bool n 79 80config HAVE_XTENSA_GPIO32 81 def_bool n 82 83config KASAN_SHADOW_OFFSET 84 hex 85 default 0x6e400000 86 87menu "Processor type and features" 88 89choice 90 prompt "Xtensa Processor Configuration" 91 default XTENSA_VARIANT_FSF 92 93config XTENSA_VARIANT_FSF 94 bool "fsf - default (not generic) configuration" 95 select MMU 96 97config XTENSA_VARIANT_DC232B 98 bool "dc232b - Diamond 232L Standard Core Rev.B (LE)" 99 select MMU 100 select HAVE_XTENSA_GPIO32 101 help 102 This variant refers to Tensilica's Diamond 232L Standard core Rev.B (LE). 103 104config XTENSA_VARIANT_DC233C 105 bool "dc233c - Diamond 233L Standard Core Rev.C (LE)" 106 select MMU 107 select HAVE_XTENSA_GPIO32 108 help 109 This variant refers to Tensilica's Diamond 233L Standard core Rev.C (LE). 110 111config XTENSA_VARIANT_CUSTOM 112 bool "Custom Xtensa processor configuration" 113 select HAVE_XTENSA_GPIO32 114 help 115 Select this variant to use a custom Xtensa processor configuration. 116 You will be prompted for a processor variant CORENAME. 117endchoice 118 119config XTENSA_VARIANT_CUSTOM_NAME 120 string "Xtensa Processor Custom Core Variant Name" 121 depends on XTENSA_VARIANT_CUSTOM 122 help 123 Provide the name of a custom Xtensa processor variant. 124 This CORENAME selects arch/xtensa/variant/CORENAME. 125 Don't forget you have to select MMU if you have one. 126 127config XTENSA_VARIANT_NAME 128 string 129 default "dc232b" if XTENSA_VARIANT_DC232B 130 default "dc233c" if XTENSA_VARIANT_DC233C 131 default "fsf" if XTENSA_VARIANT_FSF 132 default XTENSA_VARIANT_CUSTOM_NAME if XTENSA_VARIANT_CUSTOM 133 134config XTENSA_VARIANT_MMU 135 bool "Core variant has a Full MMU (TLB, Pages, Protection, etc)" 136 depends on XTENSA_VARIANT_CUSTOM 137 default y 138 select MMU 139 help 140 Build a Conventional Kernel with full MMU support, 141 ie: it supports a TLB with auto-loading, page protection. 142 143config XTENSA_VARIANT_HAVE_PERF_EVENTS 144 bool "Core variant has Performance Monitor Module" 145 depends on XTENSA_VARIANT_CUSTOM 146 default n 147 help 148 Enable if core variant has Performance Monitor Module with 149 External Registers Interface. 150 151 If unsure, say N. 152 153config XTENSA_FAKE_NMI 154 bool "Treat PMM IRQ as NMI" 155 depends on XTENSA_VARIANT_HAVE_PERF_EVENTS 156 default n 157 help 158 If PMM IRQ is the only IRQ at EXCM level it is safe to 159 treat it as NMI, which improves accuracy of profiling. 160 161 If there are other interrupts at or above PMM IRQ priority level 162 but not above the EXCM level, PMM IRQ still may be treated as NMI, 163 but only if these IRQs are not used. There will be a build warning 164 saying that this is not safe, and a bugcheck if one of these IRQs 165 actually fire. 166 167 If unsure, say N. 168 169config XTENSA_UNALIGNED_USER 170 bool "Unaligned memory access in user space" 171 help 172 The Xtensa architecture currently does not handle unaligned 173 memory accesses in hardware but through an exception handler. 174 Per default, unaligned memory accesses are disabled in user space. 175 176 Say Y here to enable unaligned memory access in user space. 177 178config HAVE_SMP 179 bool "System Supports SMP (MX)" 180 depends on XTENSA_VARIANT_CUSTOM 181 select XTENSA_MX 182 help 183 This option is used to indicate that the system-on-a-chip (SOC) 184 supports Multiprocessing. Multiprocessor support implemented above 185 the CPU core definition and currently needs to be selected manually. 186 187 Multiprocessor support is implemented with external cache and 188 interrupt controllers. 189 190 The MX interrupt distributer adds Interprocessor Interrupts 191 and causes the IRQ numbers to be increased by 4 for devices 192 like the open cores ethernet driver and the serial interface. 193 194 You still have to select "Enable SMP" to enable SMP on this SOC. 195 196config SMP 197 bool "Enable Symmetric multi-processing support" 198 depends on HAVE_SMP 199 select GENERIC_SMP_IDLE_THREAD 200 help 201 Enabled SMP Software; allows more than one CPU/CORE 202 to be activated during startup. 203 204config NR_CPUS 205 depends on SMP 206 int "Maximum number of CPUs (2-32)" 207 range 2 32 208 default "4" 209 210config HOTPLUG_CPU 211 bool "Enable CPU hotplug support" 212 depends on SMP 213 help 214 Say Y here to allow turning CPUs off and on. CPUs can be 215 controlled through /sys/devices/system/cpu. 216 217 Say N if you want to disable CPU hotplug. 218 219config FAST_SYSCALL_XTENSA 220 bool "Enable fast atomic syscalls" 221 default n 222 help 223 fast_syscall_xtensa is a syscall that can make atomic operations 224 on UP kernel when processor has no s32c1i support. 225 226 This syscall is deprecated. It may have issues when called with 227 invalid arguments. It is provided only for backwards compatibility. 228 Only enable it if your userspace software requires it. 229 230 If unsure, say N. 231 232config FAST_SYSCALL_SPILL_REGISTERS 233 bool "Enable spill registers syscall" 234 default n 235 help 236 fast_syscall_spill_registers is a syscall that spills all active 237 register windows of a calling userspace task onto its stack. 238 239 This syscall is deprecated. It may have issues when called with 240 invalid arguments. It is provided only for backwards compatibility. 241 Only enable it if your userspace software requires it. 242 243 If unsure, say N. 244 245config USER_ABI_CALL0 246 bool 247 248choice 249 prompt "Userspace ABI" 250 default USER_ABI_DEFAULT 251 help 252 Select supported userspace ABI. 253 254 If unsure, choose the default ABI. 255 256config USER_ABI_DEFAULT 257 bool "Default ABI only" 258 help 259 Assume default userspace ABI. For XEA2 cores it is windowed ABI. 260 call0 ABI binaries may be run on such kernel, but signal delivery 261 will not work correctly for them. 262 263config USER_ABI_CALL0_ONLY 264 bool "Call0 ABI only" 265 select USER_ABI_CALL0 266 help 267 Select this option to support only call0 ABI in userspace. 268 Windowed ABI binaries will crash with a segfault caused by 269 an illegal instruction exception on the first 'entry' opcode. 270 271 Choose this option if you're planning to run only user code 272 built with call0 ABI. 273 274config USER_ABI_CALL0_PROBE 275 bool "Support both windowed and call0 ABI by probing" 276 select USER_ABI_CALL0 277 help 278 Select this option to support both windowed and call0 userspace 279 ABIs. When enabled all processes are started with PS.WOE disabled 280 and a fast user exception handler for an illegal instruction is 281 used to turn on PS.WOE bit on the first 'entry' opcode executed by 282 the userspace. 283 284 This option should be enabled for the kernel that must support 285 both call0 and windowed ABIs in userspace at the same time. 286 287 Note that Xtensa ISA does not guarantee that entry opcode will 288 raise an illegal instruction exception on cores with XEA2 when 289 PS.WOE is disabled, check whether the target core supports it. 290 291endchoice 292 293endmenu 294 295config XTENSA_CALIBRATE_CCOUNT 296 def_bool n 297 help 298 On some platforms (XT2000, for example), the CPU clock rate can 299 vary. The frequency can be determined, however, by measuring 300 against a well known, fixed frequency, such as an UART oscillator. 301 302config SERIAL_CONSOLE 303 def_bool n 304 305config PLATFORM_HAVE_XIP 306 def_bool n 307 308menu "Platform options" 309 310choice 311 prompt "Xtensa System Type" 312 default XTENSA_PLATFORM_ISS 313 314config XTENSA_PLATFORM_ISS 315 bool "ISS" 316 select XTENSA_CALIBRATE_CCOUNT 317 select SERIAL_CONSOLE 318 help 319 ISS is an acronym for Tensilica's Instruction Set Simulator. 320 321config XTENSA_PLATFORM_XT2000 322 bool "XT2000" 323 select HAVE_IDE 324 help 325 XT2000 is the name of Tensilica's feature-rich emulation platform. 326 This hardware is capable of running a full Linux distribution. 327 328config XTENSA_PLATFORM_XTFPGA 329 bool "XTFPGA" 330 select ETHOC if ETHERNET 331 select PLATFORM_WANT_DEFAULT_MEM if !MMU 332 select SERIAL_CONSOLE 333 select XTENSA_CALIBRATE_CCOUNT 334 select PLATFORM_HAVE_XIP 335 help 336 XTFPGA is the name of Tensilica board family (LX60, LX110, LX200, ML605). 337 This hardware is capable of running a full Linux distribution. 338 339endchoice 340 341config PLATFORM_NR_IRQS 342 int 343 default 3 if XTENSA_PLATFORM_XT2000 344 default 0 345 346config XTENSA_CPU_CLOCK 347 int "CPU clock rate [MHz]" 348 depends on !XTENSA_CALIBRATE_CCOUNT 349 default 16 350 351config GENERIC_CALIBRATE_DELAY 352 bool "Auto calibration of the BogoMIPS value" 353 help 354 The BogoMIPS value can easily be derived from the CPU frequency. 355 356config CMDLINE_BOOL 357 bool "Default bootloader kernel arguments" 358 359config CMDLINE 360 string "Initial kernel command string" 361 depends on CMDLINE_BOOL 362 default "console=ttyS0,38400 root=/dev/ram" 363 help 364 On some architectures (EBSA110 and CATS), there is currently no way 365 for the boot loader to pass arguments to the kernel. For these 366 architectures, you should supply some command-line options at build 367 time by entering them here. As a minimum, you should specify the 368 memory size and the root device (e.g., mem=64M root=/dev/nfs). 369 370config USE_OF 371 bool "Flattened Device Tree support" 372 select OF 373 select OF_EARLY_FLATTREE 374 help 375 Include support for flattened device tree machine descriptions. 376 377config BUILTIN_DTB_SOURCE 378 string "DTB to build into the kernel image" 379 depends on OF 380 381config PARSE_BOOTPARAM 382 bool "Parse bootparam block" 383 default y 384 help 385 Parse parameters passed to the kernel from the bootloader. It may 386 be disabled if the kernel is known to run without the bootloader. 387 388 If unsure, say Y. 389 390config BLK_DEV_SIMDISK 391 tristate "Host file-based simulated block device support" 392 default n 393 depends on XTENSA_PLATFORM_ISS && BLOCK 394 help 395 Create block devices that map to files in the host file system. 396 Device binding to host file may be changed at runtime via proc 397 interface provided the device is not in use. 398 399config BLK_DEV_SIMDISK_COUNT 400 int "Number of host file-based simulated block devices" 401 range 1 10 402 depends on BLK_DEV_SIMDISK 403 default 2 404 help 405 This is the default minimal number of created block devices. 406 Kernel/module parameter 'simdisk_count' may be used to change this 407 value at runtime. More file names (but no more than 10) may be 408 specified as parameters, simdisk_count grows accordingly. 409 410config SIMDISK0_FILENAME 411 string "Host filename for the first simulated device" 412 depends on BLK_DEV_SIMDISK = y 413 default "" 414 help 415 Attach a first simdisk to a host file. Conventionally, this file 416 contains a root file system. 417 418config SIMDISK1_FILENAME 419 string "Host filename for the second simulated device" 420 depends on BLK_DEV_SIMDISK = y && BLK_DEV_SIMDISK_COUNT != 1 421 default "" 422 help 423 Another simulated disk in a host file for a buildroot-independent 424 storage. 425 426config XTFPGA_LCD 427 bool "Enable XTFPGA LCD driver" 428 depends on XTENSA_PLATFORM_XTFPGA 429 default n 430 help 431 There's a 2x16 LCD on most of XTFPGA boards, kernel may output 432 progress messages there during bootup/shutdown. It may be useful 433 during board bringup. 434 435 If unsure, say N. 436 437config XTFPGA_LCD_BASE_ADDR 438 hex "XTFPGA LCD base address" 439 depends on XTFPGA_LCD 440 default "0x0d0c0000" 441 help 442 Base address of the LCD controller inside KIO region. 443 Different boards from XTFPGA family have LCD controller at different 444 addresses. Please consult prototyping user guide for your board for 445 the correct address. Wrong address here may lead to hardware lockup. 446 447config XTFPGA_LCD_8BIT_ACCESS 448 bool "Use 8-bit access to XTFPGA LCD" 449 depends on XTFPGA_LCD 450 default n 451 help 452 LCD may be connected with 4- or 8-bit interface, 8-bit access may 453 only be used with 8-bit interface. Please consult prototyping user 454 guide for your board for the correct interface width. 455 456comment "Kernel memory layout" 457 458config INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX 459 bool "Initialize Xtensa MMU inside the Linux kernel code" 460 depends on !XTENSA_VARIANT_FSF && !XTENSA_VARIANT_DC232B 461 default y if XTENSA_VARIANT_DC233C || XTENSA_VARIANT_CUSTOM 462 help 463 Earlier version initialized the MMU in the exception vector 464 before jumping to _startup in head.S and had an advantage that 465 it was possible to place a software breakpoint at 'reset' and 466 then enter your normal kernel breakpoints once the MMU was mapped 467 to the kernel mappings (0XC0000000). 468 469 This unfortunately won't work for U-Boot and likely also wont 470 work for using KEXEC to have a hot kernel ready for doing a 471 KDUMP. 472 473 So now the MMU is initialized in head.S but it's necessary to 474 use hardware breakpoints (gdb 'hbreak' cmd) to break at _startup. 475 xt-gdb can't place a Software Breakpoint in the 0XD region prior 476 to mapping the MMU and after mapping even if the area of low memory 477 was mapped gdb wouldn't remove the breakpoint on hitting it as the 478 PC wouldn't match. Since Hardware Breakpoints are recommended for 479 Linux configurations it seems reasonable to just assume they exist 480 and leave this older mechanism for unfortunate souls that choose 481 not to follow Tensilica's recommendation. 482 483 Selecting this will cause U-Boot to set the KERNEL Load and Entry 484 address at 0x00003000 instead of the mapped std of 0xD0003000. 485 486 If in doubt, say Y. 487 488config XIP_KERNEL 489 bool "Kernel Execute-In-Place from ROM" 490 depends on PLATFORM_HAVE_XIP 491 help 492 Execute-In-Place allows the kernel to run from non-volatile storage 493 directly addressable by the CPU, such as NOR flash. This saves RAM 494 space since the text section of the kernel is not loaded from flash 495 to RAM. Read-write sections, such as the data section and stack, 496 are still copied to RAM. The XIP kernel is not compressed since 497 it has to run directly from flash, so it will take more space to 498 store it. The flash address used to link the kernel object files, 499 and for storing it, is configuration dependent. Therefore, if you 500 say Y here, you must know the proper physical address where to 501 store the kernel image depending on your own flash memory usage. 502 503 Also note that the make target becomes "make xipImage" rather than 504 "make Image" or "make uImage". The final kernel binary to put in 505 ROM memory will be arch/xtensa/boot/xipImage. 506 507 If unsure, say N. 508 509config MEMMAP_CACHEATTR 510 hex "Cache attributes for the memory address space" 511 depends on !MMU 512 default 0x22222222 513 help 514 These cache attributes are set up for noMMU systems. Each hex digit 515 specifies cache attributes for the corresponding 512MB memory 516 region: bits 0..3 -- for addresses 0x00000000..0x1fffffff, 517 bits 4..7 -- for addresses 0x20000000..0x3fffffff, and so on. 518 519 Cache attribute values are specific for the MMU type. 520 For region protection MMUs: 521 1: WT cached, 522 2: cache bypass, 523 4: WB cached, 524 f: illegal. 525 For ful MMU: 526 bit 0: executable, 527 bit 1: writable, 528 bits 2..3: 529 0: cache bypass, 530 1: WB cache, 531 2: WT cache, 532 3: special (c and e are illegal, f is reserved). 533 For MPU: 534 0: illegal, 535 1: WB cache, 536 2: WB, no-write-allocate cache, 537 3: WT cache, 538 4: cache bypass. 539 540config KSEG_PADDR 541 hex "Physical address of the KSEG mapping" 542 depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX && MMU 543 default 0x00000000 544 help 545 This is the physical address where KSEG is mapped. Please refer to 546 the chosen KSEG layout help for the required address alignment. 547 Unpacked kernel image (including vectors) must be located completely 548 within KSEG. 549 Physical memory below this address is not available to linux. 550 551 If unsure, leave the default value here. 552 553config KERNEL_VIRTUAL_ADDRESS 554 hex "Kernel virtual address" 555 depends on MMU && XIP_KERNEL 556 default 0xd0003000 557 help 558 This is the virtual address where the XIP kernel is mapped. 559 XIP kernel may be mapped into KSEG or KIO region, virtual address 560 provided here must match kernel load address provided in 561 KERNEL_LOAD_ADDRESS. 562 563config KERNEL_LOAD_ADDRESS 564 hex "Kernel load address" 565 default 0x60003000 if !MMU 566 default 0x00003000 if MMU && INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX 567 default 0xd0003000 if MMU && !INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX 568 help 569 This is the address where the kernel is loaded. 570 It is virtual address for MMUv2 configurations and physical address 571 for all other configurations. 572 573 If unsure, leave the default value here. 574 575choice 576 prompt "Relocatable vectors location" 577 default XTENSA_VECTORS_IN_TEXT 578 help 579 Choose whether relocatable vectors are merged into the kernel .text 580 or placed separately at runtime. This option does not affect 581 configurations without VECBASE register where vectors are always 582 placed at their hardware-defined locations. 583 584config XTENSA_VECTORS_IN_TEXT 585 bool "Merge relocatable vectors into kernel text" 586 depends on !MTD_XIP 587 help 588 This option puts relocatable vectors into the kernel .text section 589 with proper alignment. 590 This is a safe choice for most configurations. 591 592config XTENSA_VECTORS_SEPARATE 593 bool "Put relocatable vectors at fixed address" 594 help 595 This option puts relocatable vectors at specific virtual address. 596 Vectors are merged with the .init data in the kernel image and 597 are copied into their designated location during kernel startup. 598 Use it to put vectors into IRAM or out of FLASH on kernels with 599 XIP-aware MTD support. 600 601endchoice 602 603config VECTORS_ADDR 604 hex "Kernel vectors virtual address" 605 default 0x00000000 606 depends on XTENSA_VECTORS_SEPARATE 607 help 608 This is the virtual address of the (relocatable) vectors base. 609 It must be within KSEG if MMU is used. 610 611config XIP_DATA_ADDR 612 hex "XIP kernel data virtual address" 613 depends on XIP_KERNEL 614 default 0x00000000 615 help 616 This is the virtual address where XIP kernel data is copied. 617 It must be within KSEG if MMU is used. 618 619config PLATFORM_WANT_DEFAULT_MEM 620 def_bool n 621 622config DEFAULT_MEM_START 623 hex 624 prompt "PAGE_OFFSET/PHYS_OFFSET" if !MMU && PLATFORM_WANT_DEFAULT_MEM 625 default 0x60000000 if PLATFORM_WANT_DEFAULT_MEM 626 default 0x00000000 627 help 628 This is the base address used for both PAGE_OFFSET and PHYS_OFFSET 629 in noMMU configurations. 630 631 If unsure, leave the default value here. 632 633choice 634 prompt "KSEG layout" 635 depends on MMU 636 default XTENSA_KSEG_MMU_V2 637 638config XTENSA_KSEG_MMU_V2 639 bool "MMUv2: 128MB cached + 128MB uncached" 640 help 641 MMUv2 compatible kernel memory map: TLB way 5 maps 128MB starting 642 at KSEG_PADDR to 0xd0000000 with cache and to 0xd8000000 643 without cache. 644 KSEG_PADDR must be aligned to 128MB. 645 646config XTENSA_KSEG_256M 647 bool "256MB cached + 256MB uncached" 648 depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX 649 help 650 TLB way 6 maps 256MB starting at KSEG_PADDR to 0xb0000000 651 with cache and to 0xc0000000 without cache. 652 KSEG_PADDR must be aligned to 256MB. 653 654config XTENSA_KSEG_512M 655 bool "512MB cached + 512MB uncached" 656 depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX 657 help 658 TLB way 6 maps 512MB starting at KSEG_PADDR to 0xa0000000 659 with cache and to 0xc0000000 without cache. 660 KSEG_PADDR must be aligned to 256MB. 661 662endchoice 663 664config HIGHMEM 665 bool "High Memory Support" 666 depends on MMU 667 help 668 Linux can use the full amount of RAM in the system by 669 default. However, the default MMUv2 setup only maps the 670 lowermost 128 MB of memory linearly to the areas starting 671 at 0xd0000000 (cached) and 0xd8000000 (uncached). 672 When there are more than 128 MB memory in the system not 673 all of it can be "permanently mapped" by the kernel. 674 The physical memory that's not permanently mapped is called 675 "high memory". 676 677 If you are compiling a kernel which will never run on a 678 machine with more than 128 MB total physical RAM, answer 679 N here. 680 681 If unsure, say Y. 682 683config FORCE_MAX_ZONEORDER 684 int "Maximum zone order" 685 default "11" 686 help 687 The kernel memory allocator divides physically contiguous memory 688 blocks into "zones", where each zone is a power of two number of 689 pages. This option selects the largest power of two that the kernel 690 keeps in the memory allocator. If you need to allocate very large 691 blocks of physically contiguous memory, then you may need to 692 increase this value. 693 694 This config option is actually maximum order plus one. For example, 695 a value of 11 means that the largest free memory block is 2^10 pages. 696 697endmenu 698 699menu "Power management options" 700 701source "kernel/power/Kconfig" 702 703endmenu 704