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authorArnd Bergmann <arnd@arndb.de>2018-03-07 21:21:59 +0100
committerArnd Bergmann <arnd@arndb.de>2018-03-09 23:19:58 +0100
commitfd8773f9f544955f6f47dc2ac3ab85ad64376b7f (patch)
tree2eedaf10b5a4b62df0d3b514cec9614a6af6b563 /Documentation/frv/mmu-layout.txt
parentmn10300: Remove the architecture (diff)
downloadlinux-dev-fd8773f9f544955f6f47dc2ac3ab85ad64376b7f.tar.xz
linux-dev-fd8773f9f544955f6f47dc2ac3ab85ad64376b7f.zip
arch: remove frv port
The Fujitsu FRV kernel port has been around for a long time, but has not seen regular updates in several years and instead was marked 'Orphaned' in 2016 by long-time maintainer David Howells. The SoC product line apparently is apparently still around in the form of the Socionext Milbeaut image processor, but this one no longer uses the FRV CPU cores. This removes all FRV specific files from the kernel. Link: http://www.socionext.com/en/products/assp/milbeaut/ Cc: David Howells <dhowells@redhat.com> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
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diff --git a/Documentation/frv/mmu-layout.txt b/Documentation/frv/mmu-layout.txt
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- =================================
- FR451 MMU LINUX MEMORY MANAGEMENT
- =================================
-
-============
-MMU HARDWARE
-============
-
-FR451 MMU Linux puts the MMU into EDAT mode whilst running. This means that it uses both the SAT
-registers and the DAT TLB to perform address translation.
-
-There are 8 IAMLR/IAMPR register pairs and 16 DAMLR/DAMPR register pairs for SAT mode.
-
-In DAT mode, there is also a TLB organised in cache format as 64 lines x 2 ways. Each line spans a
-16KB range of addresses, but can match a larger region.
-
-
-===========================
-MEMORY MANAGEMENT REGISTERS
-===========================
-
-Certain control registers are used by the kernel memory management routines:
-
- REGISTERS USAGE
- ====================== ==================================================
- IAMR0, DAMR0 Kernel image and data mappings
- IAMR1, DAMR1 First-chance TLB lookup mapping
- DAMR2 Page attachment for cache flush by page
- DAMR3 Current PGD mapping
- SCR0, DAMR4 Instruction TLB PGE/PTD cache
- SCR1, DAMR5 Data TLB PGE/PTD cache
- DAMR6-10 kmap_atomic() mappings
- DAMR11 I/O mapping
- CXNR mm_struct context ID
- TTBR Page directory (PGD) pointer (physical address)
-
-
-=====================
-GENERAL MEMORY LAYOUT
-=====================
-
-The physical memory layout is as follows:
-
- PHYSICAL ADDRESS CONTROLLER DEVICE
- =================== ============== =======================================
- 00000000 - BFFFFFFF SDRAM SDRAM area
- E0000000 - EFFFFFFF L-BUS CS2# VDK SLBUS/PCI window
- F0000000 - F0FFFFFF L-BUS CS5# MB93493 CSC area (DAV daughter board)
- F1000000 - F1FFFFFF L-BUS CS7# (CB70 CPU-card PCMCIA port I/O space)
- FC000000 - FC0FFFFF L-BUS CS1# VDK MB86943 config space
- FC100000 - FC1FFFFF L-BUS CS6# DM9000 NIC I/O space
- FC200000 - FC2FFFFF L-BUS CS3# MB93493 CSR area (DAV daughter board)
- FD000000 - FDFFFFFF L-BUS CS4# (CB70 CPU-card extra flash space)
- FE000000 - FEFFFFFF Internal CPU peripherals
- FF000000 - FF1FFFFF L-BUS CS0# Flash 1
- FF200000 - FF3FFFFF L-BUS CS0# Flash 2
- FFC00000 - FFC0001F L-BUS CS0# FPGA
-
-The virtual memory layout is:
-
- VIRTUAL ADDRESS PHYSICAL TRANSLATOR FLAGS SIZE OCCUPATION
- ================= ======== ============== ======= ======= ===================================
- 00004000-BFFFFFFF various TLB,xAMR1 D-N-??V 3GB Userspace
- C0000000-CFFFFFFF 00000000 xAMPR0 -L-S--V 256MB Kernel image and data
- D0000000-D7FFFFFF various TLB,xAMR1 D-NS??V 128MB vmalloc area
- D8000000-DBFFFFFF various TLB,xAMR1 D-NS??V 64MB kmap() area
- DC000000-DCFFFFFF various TLB 1MB Secondary kmap_atomic() frame
- DD000000-DD27FFFF various DAMR 160KB Primary kmap_atomic() frame
- DD040000 DAMR2/IAMR2 -L-S--V page Page cache flush attachment point
- DD080000 DAMR3 -L-SC-V page Page Directory (PGD)
- DD0C0000 DAMR4 -L-SC-V page Cached insn TLB Page Table lookup
- DD100000 DAMR5 -L-SC-V page Cached data TLB Page Table lookup
- DD140000 DAMR6 -L-S--V page kmap_atomic(KM_BOUNCE_READ)
- DD180000 DAMR7 -L-S--V page kmap_atomic(KM_SKB_SUNRPC_DATA)
- DD1C0000 DAMR8 -L-S--V page kmap_atomic(KM_SKB_DATA_SOFTIRQ)
- DD200000 DAMR9 -L-S--V page kmap_atomic(KM_USER0)
- DD240000 DAMR10 -L-S--V page kmap_atomic(KM_USER1)
- E0000000-FFFFFFFF E0000000 DAMR11 -L-SC-V 512MB I/O region
-
-IAMPR1 and DAMPR1 are used as an extension to the TLB.
-
-
-====================
-KMAP AND KMAP_ATOMIC
-====================
-
-To access pages in the page cache (which may not be directly accessible if highmem is available),
-the kernel calls kmap(), does the access and then calls kunmap(); or it calls kmap_atomic(), does
-the access and then calls kunmap_atomic().
-
-kmap() creates an attachment between an arbitrary inaccessible page and a range of virtual
-addresses by installing a PTE in a special page table. The kernel can then access this page as it
-wills. When it's finished, the kernel calls kunmap() to clear the PTE.
-
-kmap_atomic() does something slightly different. In the interests of speed, it chooses one of two
-strategies:
-
- (1) If possible, kmap_atomic() attaches the requested page to one of DAMPR5 through DAMPR10
- register pairs; and the matching kunmap_atomic() clears the DAMPR. This makes high memory
- support really fast as there's no need to flush the TLB or modify the page tables. The DAMLR
- registers being used for this are preset during boot and don't change over the lifetime of the
- process. There's a direct mapping between the first few kmap_atomic() types, DAMR number and
- virtual address slot.
-
- However, there are more kmap_atomic() types defined than there are DAMR registers available,
- so we fall back to:
-
- (2) kmap_atomic() uses a slot in the secondary frame (determined by the type parameter), and then
- locks an entry in the TLB to translate that slot to the specified page. The number of slots is
- obviously limited, and their positions are controlled such that each slot is matched by a
- different line in the TLB. kunmap() ejects the entry from the TLB.
-
-Note that the first three kmap atomic types are really just declared as placeholders. The DAMPR
-registers involved are actually modified directly.
-
-Also note that kmap() itself may sleep, kmap_atomic() may never sleep and both always succeed;
-furthermore, a driver using kmap() may sleep before calling kunmap(), but may not sleep before
-calling kunmap_atomic() if it had previously called kmap_atomic().
-
-
-===============================
-USING MORE THAN 256MB OF MEMORY
-===============================
-
-The kernel cannot access more than 256MB of memory directly. The physical layout, however, permits
-up to 3GB of SDRAM (possibly 3.25GB) to be made available. By using CONFIG_HIGHMEM, the kernel can
-allow userspace (by way of page tables) and itself (by way of kmap) to deal with the memory
-allocation.
-
-External devices can, of course, still DMA to and from all of the SDRAM, even if the kernel can't
-see it directly. The kernel translates page references into real addresses for communicating to the
-devices.
-
-
-===================
-PAGE TABLE TOPOLOGY
-===================
-
-The page tables are arranged in 2-layer format. There is a middle layer (PMD) that would be used in
-3-layer format tables but that is folded into the top layer (PGD) and so consumes no extra memory
-or processing power.
-
- +------+ PGD PMD
- | TTBR |--->+-------------------+
- +------+ | | : STE |
- | PGE0 | PME0 : STE |
- | | : STE |
- +-------------------+ Page Table
- | | : STE -------------->+--------+ +0x0000
- | PGE1 | PME0 : STE -----------+ | PTE0 |
- | | : STE -------+ | +--------+
- +-------------------+ | | | PTE63 |
- | | : STE | | +-->+--------+ +0x0100
- | PGE2 | PME0 : STE | | | PTE64 |
- | | : STE | | +--------+
- +-------------------+ | | PTE127 |
- | | : STE | +------>+--------+ +0x0200
- | PGE3 | PME0 : STE | | PTE128 |
- | | : STE | +--------+
- +-------------------+ | PTE191 |
- +--------+ +0x0300
-
-Each Page Directory (PGD) is 16KB (page size) in size and is divided into 64 entries (PGEs). Each
-PGE contains one Page Mid Directory (PMD).
-
-Each PMD is 256 bytes in size and contains a single entry (PME). Each PME holds 64 FR451 MMU
-segment table entries of 4 bytes apiece. Each PME "points to" a page table. In practice, each STE
-points to a subset of the page table, the first to PT+0x0000, the second to PT+0x0100, the third to
-PT+0x200, and so on.
-
-Each PGE and PME covers 64MB of the total virtual address space.
-
-Each Page Table (PTD) is 16KB (page size) in size, and is divided into 4096 entries (PTEs). Each
-entry can point to one 16KB page. In practice, each Linux page table is subdivided into 64 FR451
-MMU page tables. But they are all grouped together to make management easier, in particular rmap
-support is then trivial.
-
-Grouping page tables in this fashion makes PGE caching in SCR0/SCR1 more efficient because the
-coverage of the cached item is greater.
-
-Page tables for the vmalloc area are allocated at boot time and shared between all mm_structs.
-
-
-=================
-USER SPACE LAYOUT
-=================
-
-For MMU capable Linux, the regions userspace code are allowed to access are kept entirely separate
-from those dedicated to the kernel:
-
- VIRTUAL ADDRESS SIZE PURPOSE
- ================= ===== ===================================
- 00000000-00003fff 4KB NULL pointer access trap
- 00004000-01ffffff ~32MB lower mmap space (grows up)
- 02000000-021fffff 2MB Stack space (grows down from top)
- 02200000-nnnnnnnn Executable mapping
- nnnnnnnn- brk space (grows up)
- -bfffffff upper mmap space (grows down)
-
-This is so arranged so as to make best use of the 16KB page tables and the way in which PGEs/PMEs
-are cached by the TLB handler. The lower mmap space is filled first, and then the upper mmap space
-is filled.
-
-
-===============================
-GDB-STUB MMU DEBUGGING SERVICES
-===============================
-
-The gdb-stub included in this kernel provides a number of services to aid in the debugging of MMU
-related kernel services:
-
- (*) Every time the kernel stops, certain state information is dumped into __debug_mmu. This
- variable is defined in arch/frv/kernel/gdb-stub.c. Note that the gdbinit file in this
- directory has some useful macros for dealing with this.
-
- (*) __debug_mmu.tlb[]
-
- This receives the current TLB contents. This can be viewed with the _tlb GDB macro:
-
- (gdb) _tlb
- tlb[0x00]: 01000005 00718203 01000002 00718203
- tlb[0x01]: 01004002 006d4201 01004005 006d4203
- tlb[0x02]: 01008002 006d0201 01008006 00004200
- tlb[0x03]: 0100c006 007f4202 0100c002 0064c202
- tlb[0x04]: 01110005 00774201 01110002 00774201
- tlb[0x05]: 01114005 00770201 01114002 00770201
- tlb[0x06]: 01118002 0076c201 01118005 0076c201
- ...
- tlb[0x3d]: 010f4002 00790200 001f4002 0054ca02
- tlb[0x3e]: 010f8005 0078c201 010f8002 0078c201
- tlb[0x3f]: 001fc002 0056ca01 001fc005 00538a01
-
- (*) __debug_mmu.iamr[]
- (*) __debug_mmu.damr[]
-
- These receive the current IAMR and DAMR contents. These can be viewed with the _amr
- GDB macro:
-
- (gdb) _amr
- AMRx DAMR IAMR
- ==== ===================== =====================
- amr0 : L:c0000000 P:00000cb9 : L:c0000000 P:000004b9
- amr1 : L:01070005 P:006f9203 : L:0102c005 P:006a1201
- amr2 : L:d8d00000 P:00000000 : L:d8d00000 P:00000000
- amr3 : L:d8d04000 P:00534c0d : L:00000000 P:00000000
- amr4 : L:d8d08000 P:00554c0d : L:00000000 P:00000000
- amr5 : L:d8d0c000 P:00554c0d : L:00000000 P:00000000
- amr6 : L:d8d10000 P:00000000 : L:00000000 P:00000000
- amr7 : L:d8d14000 P:00000000 : L:00000000 P:00000000
- amr8 : L:d8d18000 P:00000000
- amr9 : L:d8d1c000 P:00000000
- amr10: L:d8d20000 P:00000000
- amr11: L:e0000000 P:e0000ccd
-
- (*) The current task's page directory is bound to DAMR3.
-
- This can be viewed with the _pgd GDB macro:
-
- (gdb) _pgd
- $3 = {{pge = {{ste = {0x554001, 0x554101, 0x554201, 0x554301, 0x554401,
- 0x554501, 0x554601, 0x554701, 0x554801, 0x554901, 0x554a01,
- 0x554b01, 0x554c01, 0x554d01, 0x554e01, 0x554f01, 0x555001,
- 0x555101, 0x555201, 0x555301, 0x555401, 0x555501, 0x555601,
- 0x555701, 0x555801, 0x555901, 0x555a01, 0x555b01, 0x555c01,
- 0x555d01, 0x555e01, 0x555f01, 0x556001, 0x556101, 0x556201,
- 0x556301, 0x556401, 0x556501, 0x556601, 0x556701, 0x556801,
- 0x556901, 0x556a01, 0x556b01, 0x556c01, 0x556d01, 0x556e01,
- 0x556f01, 0x557001, 0x557101, 0x557201, 0x557301, 0x557401,
- 0x557501, 0x557601, 0x557701, 0x557801, 0x557901, 0x557a01,
- 0x557b01, 0x557c01, 0x557d01, 0x557e01, 0x557f01}}}}, {pge = {{
- ste = {0x0 <repeats 64 times>}}}} <repeats 51 times>, {pge = {{ste = {
- 0x248001, 0x248101, 0x248201, 0x248301, 0x248401, 0x248501,
- 0x248601, 0x248701, 0x248801, 0x248901, 0x248a01, 0x248b01,
- 0x248c01, 0x248d01, 0x248e01, 0x248f01, 0x249001, 0x249101,
- 0x249201, 0x249301, 0x249401, 0x249501, 0x249601, 0x249701,
- 0x249801, 0x249901, 0x249a01, 0x249b01, 0x249c01, 0x249d01,
- 0x249e01, 0x249f01, 0x24a001, 0x24a101, 0x24a201, 0x24a301,
- 0x24a401, 0x24a501, 0x24a601, 0x24a701, 0x24a801, 0x24a901,
- 0x24aa01, 0x24ab01, 0x24ac01, 0x24ad01, 0x24ae01, 0x24af01,
- 0x24b001, 0x24b101, 0x24b201, 0x24b301, 0x24b401, 0x24b501,
- 0x24b601, 0x24b701, 0x24b801, 0x24b901, 0x24ba01, 0x24bb01,
- 0x24bc01, 0x24bd01, 0x24be01, 0x24bf01}}}}, {pge = {{ste = {
- 0x0 <repeats 64 times>}}}} <repeats 11 times>}
-
- (*) The PTD last used by the instruction TLB miss handler is attached to DAMR4.
- (*) The PTD last used by the data TLB miss handler is attached to DAMR5.
-
- These can be viewed with the _ptd_i and _ptd_d GDB macros:
-
- (gdb) _ptd_d
- $5 = {{pte = 0x0} <repeats 127 times>, {pte = 0x539b01}, {
- pte = 0x0} <repeats 896 times>, {pte = 0x719303}, {pte = 0x6d5303}, {
- pte = 0x0}, {pte = 0x0}, {pte = 0x0}, {pte = 0x0}, {pte = 0x0}, {
- pte = 0x0}, {pte = 0x0}, {pte = 0x0}, {pte = 0x0}, {pte = 0x6a1303}, {
- pte = 0x0} <repeats 12 times>, {pte = 0x709303}, {pte = 0x0}, {pte = 0x0},
- {pte = 0x6fd303}, {pte = 0x6f9303}, {pte = 0x6f5303}, {pte = 0x0}, {
- pte = 0x6ed303}, {pte = 0x531b01}, {pte = 0x50db01}, {
- pte = 0x0} <repeats 13 times>, {pte = 0x5303}, {pte = 0x7f5303}, {
- pte = 0x509b01}, {pte = 0x505b01}, {pte = 0x7c9303}, {pte = 0x7b9303}, {
- pte = 0x7b5303}, {pte = 0x7b1303}, {pte = 0x7ad303}, {pte = 0x0}, {
- pte = 0x0}, {pte = 0x7a1303}, {pte = 0x0}, {pte = 0x795303}, {pte = 0x0}, {
- pte = 0x78d303}, {pte = 0x0}, {pte = 0x0}, {pte = 0x0}, {pte = 0x0}, {
- pte = 0x0}, {pte = 0x775303}, {pte = 0x771303}, {pte = 0x76d303}, {
- pte = 0x0}, {pte = 0x765303}, {pte = 0x7c5303}, {pte = 0x501b01}, {
- pte = 0x4f1b01}, {pte = 0x4edb01}, {pte = 0x0}, {pte = 0x4f9b01}, {
- pte = 0x4fdb01}, {pte = 0x0} <repeats 2992 times>}