From b22da3d8526a935aa31e086e63f60ff3246cb61c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Sat, 09 Dec 2023 07:24:11 +0000
Subject: [PATCH] add stmac read mac form eeprom

---
 kernel/arch/xtensa/Kconfig |  512 +++++++++++++++++++++++++++++++++++---------------------
 1 files changed, 316 insertions(+), 196 deletions(-)

diff --git a/kernel/arch/xtensa/Kconfig b/kernel/arch/xtensa/Kconfig
index d9b0709..03cbf6b 100644
--- a/kernel/arch/xtensa/Kconfig
+++ b/kernel/arch/xtensa/Kconfig
@@ -1,26 +1,31 @@
 # SPDX-License-Identifier: GPL-2.0
-config ZONE_DMA
-	def_bool y
-
 config XTENSA
 	def_bool y
-	select ARCH_HAS_SG_CHAIN
-	select ARCH_HAS_SYNC_DMA_FOR_CPU
-	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
-	select ARCH_NO_COHERENT_DMA_MMAP if !MMU
+	select ARCH_32BIT_OFF_T
+	select ARCH_HAS_BINFMT_FLAT if !MMU
+	select ARCH_HAS_DMA_PREP_COHERENT if MMU
+	select ARCH_HAS_SYNC_DMA_FOR_CPU if MMU
+	select ARCH_HAS_SYNC_DMA_FOR_DEVICE if MMU
+	select ARCH_HAS_DMA_SET_UNCACHED if MMU
+	select ARCH_USE_QUEUED_RWLOCKS
+	select ARCH_USE_QUEUED_SPINLOCKS
 	select ARCH_WANT_FRAME_POINTERS
 	select ARCH_WANT_IPC_PARSE_VERSION
-	select BUILDTIME_EXTABLE_SORT
+	select BUILDTIME_TABLE_SORT
 	select CLONE_BACKWARDS
 	select COMMON_CLK
-	select DMA_NONCOHERENT_OPS
+	select DMA_REMAP if MMU
 	select GENERIC_ATOMIC64
 	select GENERIC_CLOCKEVENTS
 	select GENERIC_IRQ_SHOW
 	select GENERIC_PCI_IOMAP
 	select GENERIC_SCHED_CLOCK
 	select GENERIC_STRNCPY_FROM_USER if KASAN
-	select HAVE_ARCH_KASAN if MMU
+	select HAVE_ARCH_AUDITSYSCALL
+	select HAVE_ARCH_JUMP_LABEL if !XIP_KERNEL
+	select HAVE_ARCH_KASAN if MMU && !XIP_KERNEL
+	select HAVE_ARCH_SECCOMP_FILTER
+	select HAVE_ARCH_TRACEHOOK
 	select HAVE_DEBUG_KMEMLEAK
 	select HAVE_DMA_CONTIGUOUS
 	select HAVE_EXIT_THREAD
@@ -28,14 +33,15 @@
 	select HAVE_FUTEX_CMPXCHG if !MMU && FUTEX
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS
 	select HAVE_IRQ_TIME_ACCOUNTING
-	select HAVE_MEMBLOCK
 	select HAVE_OPROFILE
+	select HAVE_PCI
 	select HAVE_PERF_EVENTS
 	select HAVE_STACKPROTECTOR
+	select HAVE_SYSCALL_TRACEPOINTS
 	select IRQ_DOMAIN
 	select MODULES_USE_ELF_RELA
-	select NO_BOOTMEM
 	select PERF_USE_VMALLOC
+	select SET_FS
 	select VIRT_TO_BUS
 	help
 	  Xtensa processors are 32-bit RISC machines designed by Tensilica
@@ -44,9 +50,6 @@
 	  architecture supports all processor configurations and extensions,
 	  with reasonable minimum requirements.  The Xtensa Linux project has
 	  a home page at <http://www.linux-xtensa.org/>.
-
-config RWSEM_XCHGADD_ALGORITHM
-	def_bool y
 
 config GENERIC_HWEIGHT
 	def_bool y
@@ -121,7 +124,7 @@
 	help
 	  Provide the name of a custom Xtensa processor variant.
 	  This CORENAME selects arch/xtensa/variant/CORENAME.
-	  Dont forget you have to select MMU if you have one.
+	  Don't forget you have to select MMU if you have one.
 
 config XTENSA_VARIANT_NAME
 	string
@@ -166,7 +169,7 @@
 	  If unsure, say N.
 
 config XTENSA_UNALIGNED_USER
-	bool "Unaligned memory access in use space"
+	bool "Unaligned memory access in user space"
 	help
 	  The Xtensa architecture currently does not handle unaligned
 	  memory accesses in hardware but through an exception handler.
@@ -179,11 +182,11 @@
 	depends on XTENSA_VARIANT_CUSTOM
 	select XTENSA_MX
 	help
-	  This option is use to indicate that the system-on-a-chip (SOC)
+	  This option is used to indicate that the system-on-a-chip (SOC)
 	  supports Multiprocessing. Multiprocessor support implemented above
 	  the CPU core definition and currently needs to be selected manually.
 
-	  Multiprocessor support in implemented with external cache and
+	  Multiprocessor support is implemented with external cache and
 	  interrupt controllers.
 
 	  The MX interrupt distributer adds Interprocessor Interrupts
@@ -215,137 +218,6 @@
 
 	  Say N if you want to disable CPU hotplug.
 
-config INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
-	bool "Initialize Xtensa MMU inside the Linux kernel code"
-	depends on !XTENSA_VARIANT_FSF && !XTENSA_VARIANT_DC232B
-	default y if XTENSA_VARIANT_DC233C || XTENSA_VARIANT_CUSTOM
-	help
-	  Earlier version initialized the MMU in the exception vector
-	  before jumping to _startup in head.S and had an advantage that
-	  it was possible to place a software breakpoint at 'reset' and
-	  then enter your normal kernel breakpoints once the MMU was mapped
-	  to the kernel mappings (0XC0000000).
-
-	  This unfortunately won't work for U-Boot and likely also wont
-	  work for using KEXEC to have a hot kernel ready for doing a
-	  KDUMP.
-
-	  So now the MMU is initialized in head.S but it's necessary to
-	  use hardware breakpoints (gdb 'hbreak' cmd) to break at _startup.
-	  xt-gdb can't place a Software Breakpoint in the  0XD region prior
-	  to mapping the MMU and after mapping even if the area of low memory
-	  was mapped gdb wouldn't remove the breakpoint on hitting it as the
-	  PC wouldn't match. Since Hardware Breakpoints are recommended for
-	  Linux configurations it seems reasonable to just assume they exist
-	  and leave this older mechanism for unfortunate souls that choose
-	  not to follow Tensilica's recommendation.
-
-	  Selecting this will cause U-Boot to set the KERNEL Load and Entry
-	  address at 0x00003000 instead of the mapped std of 0xD0003000.
-
-	  If in doubt, say Y.
-
-config MEMMAP_CACHEATTR
-	hex "Cache attributes for the memory address space"
-	depends on !MMU
-	default 0x22222222
-	help
-	  These cache attributes are set up for noMMU systems. Each hex digit
-	  specifies cache attributes for the corresponding 512MB memory
-	  region: bits 0..3 -- for addresses 0x00000000..0x1fffffff,
-	  bits 4..7 -- for addresses 0x20000000..0x3fffffff, and so on.
-
-	  Cache attribute values are specific for the MMU type, so e.g.
-	  for region protection MMUs: 2 is cache bypass, 4 is WB cached,
-	  1 is WT cached, f is illegal. For ful MMU: bit 0 makes it executable,
-	  bit 1 makes it writable, bits 2..3 meaning is 0: cache bypass,
-	  1: WB cache, 2: WT cache, 3: special (c and e are illegal, f is
-	  reserved).
-
-config KSEG_PADDR
-	hex "Physical address of the KSEG mapping"
-	depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX && MMU
-	default 0x00000000
-	help
-	  This is the physical address where KSEG is mapped. Please refer to
-	  the chosen KSEG layout help for the required address alignment.
-	  Unpacked kernel image (including vectors) must be located completely
-	  within KSEG.
-	  Physical memory below this address is not available to linux.
-
-	  If unsure, leave the default value here.
-
-config KERNEL_LOAD_ADDRESS
-	hex "Kernel load address"
-	default 0x60003000 if !MMU
-	default 0x00003000 if MMU && INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
-	default 0xd0003000 if MMU && !INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
-	help
-	  This is the address where the kernel is loaded.
-	  It is virtual address for MMUv2 configurations and physical address
-	  for all other configurations.
-
-	  If unsure, leave the default value here.
-
-config VECTORS_OFFSET
-	hex "Kernel vectors offset"
-	default 0x00003000
-	help
-	  This is the offset of the kernel image from the relocatable vectors
-	  base.
-
-	  If unsure, leave the default value here.
-
-choice
-	prompt "KSEG layout"
-	depends on MMU
-	default XTENSA_KSEG_MMU_V2
-
-config XTENSA_KSEG_MMU_V2
-	bool "MMUv2: 128MB cached + 128MB uncached"
-	help
-	  MMUv2 compatible kernel memory map: TLB way 5 maps 128MB starting
-	  at KSEG_PADDR to 0xd0000000 with cache and to 0xd8000000
-	  without cache.
-	  KSEG_PADDR must be aligned to 128MB.
-
-config XTENSA_KSEG_256M
-	bool "256MB cached + 256MB uncached"
-	depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
-	help
-	  TLB way 6 maps 256MB starting at KSEG_PADDR to 0xb0000000
-	  with cache and to 0xc0000000 without cache.
-	  KSEG_PADDR must be aligned to 256MB.
-
-config XTENSA_KSEG_512M
-	bool "512MB cached + 512MB uncached"
-	depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
-	help
-	  TLB way 6 maps 512MB starting at KSEG_PADDR to 0xa0000000
-	  with cache and to 0xc0000000 without cache.
-	  KSEG_PADDR must be aligned to 256MB.
-
-endchoice
-
-config HIGHMEM
-	bool "High Memory Support"
-	depends on MMU
-	help
-	  Linux can use the full amount of RAM in the system by
-	  default. However, the default MMUv2 setup only maps the
-	  lowermost 128 MB of memory linearly to the areas starting
-	  at 0xd0000000 (cached) and 0xd8000000 (uncached).
-	  When there are more than 128 MB memory in the system not
-	  all of it can be "permanently mapped" by the kernel.
-	  The physical memory that's not permanently mapped is called
-	  "high memory".
-
-	  If you are compiling a kernel which will never run on a
-	  machine with more than 128 MB total physical RAM, answer
-	  N here.
-
-	  If unsure, say Y.
-
 config FAST_SYSCALL_XTENSA
 	bool "Enable fast atomic syscalls"
 	default n
@@ -372,6 +244,54 @@
 
 	  If unsure, say N.
 
+config USER_ABI_CALL0
+	bool
+
+choice
+	prompt "Userspace ABI"
+	default USER_ABI_DEFAULT
+	help
+	  Select supported userspace ABI.
+
+	  If unsure, choose the default ABI.
+
+config USER_ABI_DEFAULT
+	bool "Default ABI only"
+	help
+	  Assume default userspace ABI. For XEA2 cores it is windowed ABI.
+	  call0 ABI binaries may be run on such kernel, but signal delivery
+	  will not work correctly for them.
+
+config USER_ABI_CALL0_ONLY
+	bool "Call0 ABI only"
+	select USER_ABI_CALL0
+	help
+	  Select this option to support only call0 ABI in userspace.
+	  Windowed ABI binaries will crash with a segfault caused by
+	  an illegal instruction exception on the first 'entry' opcode.
+
+	  Choose this option if you're planning to run only user code
+	  built with call0 ABI.
+
+config USER_ABI_CALL0_PROBE
+	bool "Support both windowed and call0 ABI by probing"
+	select USER_ABI_CALL0
+	help
+	  Select this option to support both windowed and call0 userspace
+	  ABIs. When enabled all processes are started with PS.WOE disabled
+	  and a fast user exception handler for an illegal instruction is
+	  used to turn on PS.WOE bit on the first 'entry' opcode executed by
+	  the userspace.
+
+	  This option should be enabled for the kernel that must support
+	  both call0 and windowed ABIs in userspace at the same time.
+
+	  Note that Xtensa ISA does not guarantee that entry opcode will
+	  raise an illegal instruction exception on cores with XEA2 when
+	  PS.WOE is disabled, check whether the target core supports it.
+
+endchoice
+
 endmenu
 
 config XTENSA_CALIBRATE_CCOUNT
@@ -384,20 +304,8 @@
 config SERIAL_CONSOLE
 	def_bool n
 
-menu "Bus options"
-
-config PCI
-	bool "PCI support"
-	default y
-	help
-	  Find out whether you have a PCI motherboard. PCI is the name of a
-	  bus system, i.e. the way the CPU talks to the other stuff inside
-	  your box. Other bus systems are ISA, EISA, MicroChannel (MCA) or
-	  VESA. If you have PCI, say Y, otherwise N.
-
-source "drivers/pci/Kconfig"
-
-endmenu
+config PLATFORM_HAVE_XIP
+	def_bool n
 
 menu "Platform options"
 
@@ -425,6 +333,7 @@
 	select PLATFORM_WANT_DEFAULT_MEM if !MMU
 	select SERIAL_CONSOLE
 	select XTENSA_CALIBRATE_CCOUNT
+	select PLATFORM_HAVE_XIP
 	help
 	  XTFPGA is the name of Tensilica board family (LX60, LX110, LX200, ML605).
 	  This hardware is capable of running a full Linux distribution.
@@ -464,11 +373,10 @@
 	bool "Flattened Device Tree support"
 	select OF
 	select OF_EARLY_FLATTREE
-	select OF_RESERVED_MEM
 	help
 	  Include support for flattened device tree machine descriptions.
 
-config BUILTIN_DTB
+config BUILTIN_DTB_SOURCE
 	string "DTB to build into the kernel image"
 	depends on OF
 
@@ -517,36 +425,6 @@
 	  Another simulated disk in a host file for a buildroot-independent
 	  storage.
 
-config FORCE_MAX_ZONEORDER
-	int "Maximum zone order"
-	default "11"
-	help
-	  The kernel memory allocator divides physically contiguous memory
-	  blocks into "zones", where each zone is a power of two number of
-	  pages.  This option selects the largest power of two that the kernel
-	  keeps in the memory allocator.  If you need to allocate very large
-	  blocks of physically contiguous memory, then you may need to
-	  increase this value.
-
-	  This config option is actually maximum order plus one. For example,
-	  a value of 11 means that the largest free memory block is 2^10 pages.
-
-source "drivers/pcmcia/Kconfig"
-
-config PLATFORM_WANT_DEFAULT_MEM
-	def_bool n
-
-config DEFAULT_MEM_START
-	hex
-	prompt "PAGE_OFFSET/PHYS_OFFSET" if !MMU && PLATFORM_WANT_DEFAULT_MEM
-	default 0x60000000 if PLATFORM_WANT_DEFAULT_MEM
-	default 0x00000000
-	help
-	  This is the base address used for both PAGE_OFFSET and PHYS_OFFSET
-	  in noMMU configurations.
-
-	  If unsure, leave the default value here.
-
 config XTFPGA_LCD
 	bool "Enable XTFPGA LCD driver"
 	depends on XTENSA_PLATFORM_XTFPGA
@@ -577,6 +455,248 @@
 	  only be used with 8-bit interface. Please consult prototyping user
 	  guide for your board for the correct interface width.
 
+comment "Kernel memory layout"
+
+config INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
+	bool "Initialize Xtensa MMU inside the Linux kernel code"
+	depends on !XTENSA_VARIANT_FSF && !XTENSA_VARIANT_DC232B
+	default y if XTENSA_VARIANT_DC233C || XTENSA_VARIANT_CUSTOM
+	help
+	  Earlier version initialized the MMU in the exception vector
+	  before jumping to _startup in head.S and had an advantage that
+	  it was possible to place a software breakpoint at 'reset' and
+	  then enter your normal kernel breakpoints once the MMU was mapped
+	  to the kernel mappings (0XC0000000).
+
+	  This unfortunately won't work for U-Boot and likely also wont
+	  work for using KEXEC to have a hot kernel ready for doing a
+	  KDUMP.
+
+	  So now the MMU is initialized in head.S but it's necessary to
+	  use hardware breakpoints (gdb 'hbreak' cmd) to break at _startup.
+	  xt-gdb can't place a Software Breakpoint in the  0XD region prior
+	  to mapping the MMU and after mapping even if the area of low memory
+	  was mapped gdb wouldn't remove the breakpoint on hitting it as the
+	  PC wouldn't match. Since Hardware Breakpoints are recommended for
+	  Linux configurations it seems reasonable to just assume they exist
+	  and leave this older mechanism for unfortunate souls that choose
+	  not to follow Tensilica's recommendation.
+
+	  Selecting this will cause U-Boot to set the KERNEL Load and Entry
+	  address at 0x00003000 instead of the mapped std of 0xD0003000.
+
+	  If in doubt, say Y.
+
+config XIP_KERNEL
+	bool "Kernel Execute-In-Place from ROM"
+	depends on PLATFORM_HAVE_XIP
+	help
+	  Execute-In-Place allows the kernel to run from non-volatile storage
+	  directly addressable by the CPU, such as NOR flash. This saves RAM
+	  space since the text section of the kernel is not loaded from flash
+	  to RAM. Read-write sections, such as the data section and stack,
+	  are still copied to RAM. The XIP kernel is not compressed since
+	  it has to run directly from flash, so it will take more space to
+	  store it. The flash address used to link the kernel object files,
+	  and for storing it, is configuration dependent. Therefore, if you
+	  say Y here, you must know the proper physical address where to
+	  store the kernel image depending on your own flash memory usage.
+
+	  Also note that the make target becomes "make xipImage" rather than
+	  "make Image" or "make uImage". The final kernel binary to put in
+	  ROM memory will be arch/xtensa/boot/xipImage.
+
+	  If unsure, say N.
+
+config MEMMAP_CACHEATTR
+	hex "Cache attributes for the memory address space"
+	depends on !MMU
+	default 0x22222222
+	help
+	  These cache attributes are set up for noMMU systems. Each hex digit
+	  specifies cache attributes for the corresponding 512MB memory
+	  region: bits 0..3 -- for addresses 0x00000000..0x1fffffff,
+	  bits 4..7 -- for addresses 0x20000000..0x3fffffff, and so on.
+
+	  Cache attribute values are specific for the MMU type.
+	  For region protection MMUs:
+	    1: WT cached,
+	    2: cache bypass,
+	    4: WB cached,
+	    f: illegal.
+	  For full MMU:
+	    bit 0: executable,
+	    bit 1: writable,
+	    bits 2..3:
+	      0: cache bypass,
+	      1: WB cache,
+	      2: WT cache,
+	      3: special (c and e are illegal, f is reserved).
+	  For MPU:
+	    0: illegal,
+	    1: WB cache,
+	    2: WB, no-write-allocate cache,
+	    3: WT cache,
+	    4: cache bypass.
+
+config KSEG_PADDR
+	hex "Physical address of the KSEG mapping"
+	depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX && MMU
+	default 0x00000000
+	help
+	  This is the physical address where KSEG is mapped. Please refer to
+	  the chosen KSEG layout help for the required address alignment.
+	  Unpacked kernel image (including vectors) must be located completely
+	  within KSEG.
+	  Physical memory below this address is not available to linux.
+
+	  If unsure, leave the default value here.
+
+config KERNEL_VIRTUAL_ADDRESS
+	hex "Kernel virtual address"
+	depends on MMU && XIP_KERNEL
+	default 0xd0003000
+	help
+	  This is the virtual address where the XIP kernel is mapped.
+	  XIP kernel may be mapped into KSEG or KIO region, virtual address
+	  provided here must match kernel load address provided in
+	  KERNEL_LOAD_ADDRESS.
+
+config KERNEL_LOAD_ADDRESS
+	hex "Kernel load address"
+	default 0x60003000 if !MMU
+	default 0x00003000 if MMU && INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
+	default 0xd0003000 if MMU && !INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
+	help
+	  This is the address where the kernel is loaded.
+	  It is virtual address for MMUv2 configurations and physical address
+	  for all other configurations.
+
+	  If unsure, leave the default value here.
+
+choice
+	prompt "Relocatable vectors location"
+	default XTENSA_VECTORS_IN_TEXT
+	help
+	  Choose whether relocatable vectors are merged into the kernel .text
+	  or placed separately at runtime. This option does not affect
+	  configurations without VECBASE register where vectors are always
+	  placed at their hardware-defined locations.
+
+config XTENSA_VECTORS_IN_TEXT
+	bool "Merge relocatable vectors into kernel text"
+	depends on !MTD_XIP
+	help
+	  This option puts relocatable vectors into the kernel .text section
+	  with proper alignment.
+	  This is a safe choice for most configurations.
+
+config XTENSA_VECTORS_SEPARATE
+	bool "Put relocatable vectors at fixed address"
+	help
+	  This option puts relocatable vectors at specific virtual address.
+	  Vectors are merged with the .init data in the kernel image and
+	  are copied into their designated location during kernel startup.
+	  Use it to put vectors into IRAM or out of FLASH on kernels with
+	  XIP-aware MTD support.
+
+endchoice
+
+config VECTORS_ADDR
+	hex "Kernel vectors virtual address"
+	default 0x00000000
+	depends on XTENSA_VECTORS_SEPARATE
+	help
+	  This is the virtual address of the (relocatable) vectors base.
+	  It must be within KSEG if MMU is used.
+
+config XIP_DATA_ADDR
+	hex "XIP kernel data virtual address"
+	depends on XIP_KERNEL
+	default 0x00000000
+	help
+	  This is the virtual address where XIP kernel data is copied.
+	  It must be within KSEG if MMU is used.
+
+config PLATFORM_WANT_DEFAULT_MEM
+	def_bool n
+
+config DEFAULT_MEM_START
+	hex
+	prompt "PAGE_OFFSET/PHYS_OFFSET" if !MMU && PLATFORM_WANT_DEFAULT_MEM
+	default 0x60000000 if PLATFORM_WANT_DEFAULT_MEM
+	default 0x00000000
+	help
+	  This is the base address used for both PAGE_OFFSET and PHYS_OFFSET
+	  in noMMU configurations.
+
+	  If unsure, leave the default value here.
+
+choice
+	prompt "KSEG layout"
+	depends on MMU
+	default XTENSA_KSEG_MMU_V2
+
+config XTENSA_KSEG_MMU_V2
+	bool "MMUv2: 128MB cached + 128MB uncached"
+	help
+	  MMUv2 compatible kernel memory map: TLB way 5 maps 128MB starting
+	  at KSEG_PADDR to 0xd0000000 with cache and to 0xd8000000
+	  without cache.
+	  KSEG_PADDR must be aligned to 128MB.
+
+config XTENSA_KSEG_256M
+	bool "256MB cached + 256MB uncached"
+	depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
+	help
+	  TLB way 6 maps 256MB starting at KSEG_PADDR to 0xb0000000
+	  with cache and to 0xc0000000 without cache.
+	  KSEG_PADDR must be aligned to 256MB.
+
+config XTENSA_KSEG_512M
+	bool "512MB cached + 512MB uncached"
+	depends on INITIALIZE_XTENSA_MMU_INSIDE_VMLINUX
+	help
+	  TLB way 6 maps 512MB starting at KSEG_PADDR to 0xa0000000
+	  with cache and to 0xc0000000 without cache.
+	  KSEG_PADDR must be aligned to 256MB.
+
+endchoice
+
+config HIGHMEM
+	bool "High Memory Support"
+	depends on MMU
+	select KMAP_LOCAL
+	help
+	  Linux can use the full amount of RAM in the system by
+	  default. However, the default MMUv2 setup only maps the
+	  lowermost 128 MB of memory linearly to the areas starting
+	  at 0xd0000000 (cached) and 0xd8000000 (uncached).
+	  When there are more than 128 MB memory in the system not
+	  all of it can be "permanently mapped" by the kernel.
+	  The physical memory that's not permanently mapped is called
+	  "high memory".
+
+	  If you are compiling a kernel which will never run on a
+	  machine with more than 128 MB total physical RAM, answer
+	  N here.
+
+	  If unsure, say Y.
+
+config FORCE_MAX_ZONEORDER
+	int "Maximum zone order"
+	default "11"
+	help
+	  The kernel memory allocator divides physically contiguous memory
+	  blocks into "zones", where each zone is a power of two number of
+	  pages.  This option selects the largest power of two that the kernel
+	  keeps in the memory allocator.  If you need to allocate very large
+	  blocks of physically contiguous memory, then you may need to
+	  increase this value.
+
+	  This config option is actually maximum order plus one. For example,
+	  a value of 11 means that the largest free memory block is 2^10 pages.
+
 endmenu
 
 menu "Power management options"

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