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ARM: pgtable: document mapping types 

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2015-07-01 15:23:10 +01:00
parent 20a1080dff
commit 9ab79bb22c
1 changed files with 30 additions and 1 deletions
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31
arch/arm/include/asm/pgtable-2level.h
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@ -129,7 +129,36 @@
/*
* These are the memory types, defined to be compatible with
* pre-ARMv6 CPUs cacheable and bufferable bits: XXCB
* pre-ARMv6 CPUs cacheable and bufferable bits: n/a,n/a,C,B
* ARMv6+ without TEX remapping, they are a table index.
* ARMv6+ with TEX remapping, they correspond to n/a,TEX(0),C,B
*
* MT type Pre-ARMv6 ARMv6+ type / cacheable status
* UNCACHED Uncached Strongly ordered
* BUFFERABLE Bufferable Normal memory / non-cacheable
* WRITETHROUGH Writethrough Normal memory / write through
* WRITEBACK Writeback Normal memory / write back, read alloc
* MINICACHE Minicache N/A
* WRITEALLOC Writeback Normal memory / write back, write alloc
* DEV_SHARED Uncached Device memory (shared)
* DEV_NONSHARED Uncached Device memory (non-shared)
* DEV_WC Bufferable Normal memory / non-cacheable
* DEV_CACHED Writeback Normal memory / write back, read alloc
* VECTORS Variable Normal memory / variable
*
* All normal memory mappings have the following properties:
* - reads can be repeated with no side effects
* - repeated reads return the last value written
* - reads can fetch additional locations without side effects
* - writes can be repeated (in certain cases) with no side effects
* - writes can be merged before accessing the target
* - unaligned accesses can be supported
*
* All device mappings have the following properties:
* - no access speculation
* - no repetition (eg, on return from an exception)
* - number, order and size of accesses are maintained
* - unaligned accesses are "unpredictable"
*/
#define L_PTE_MT_UNCACHED (_AT(pteval_t, 0x00) << 2) /* 0000 */
#define L_PTE_MT_BUFFERABLE (_AT(pteval_t, 0x01) << 2) /* 0001 */