diff options
Diffstat (limited to 'arch/parisc/include/asm/fixmap.h')
| -rw-r--r-- | arch/parisc/include/asm/fixmap.h | 25 |
1 files changed, 20 insertions, 5 deletions
diff --git a/arch/parisc/include/asm/fixmap.h b/arch/parisc/include/asm/fixmap.h index e480b2c05407..5cd80ce1163a 100644 --- a/arch/parisc/include/asm/fixmap.h +++ b/arch/parisc/include/asm/fixmap.h @@ -9,12 +9,27 @@ * * All of the values in this file must be <4GB (because of assembly * loading restrictions). If you place this region anywhere above - * __PAGE_OFFSET, you must adjust the memory map accordingly */ + * __PAGE_OFFSET, you must adjust the memory map accordingly + */ -/* The alias region is used in kernel space to do copy/clear to or - * from areas congruently mapped with user space. It is 8MB large - * and must be 16MB aligned */ -#define TMPALIAS_MAP_START ((__PAGE_OFFSET) - 16*1024*1024) +/* + * The tmpalias region is used in kernel space to copy/clear/flush data + * from pages congruently mapped with user space. It is comprised of + * a pair regions. The size of these regions is determined by the largest + * cache aliasing boundary for machines that support equivalent aliasing. + * + * The c3750 with PA8700 processor returns an alias value of 11. This + * indicates that it has an alias boundary of 4 MB. It also supports + * non-equivalent aliasing without a performance penalty. + * + * Machines with PA8800/PA8900 processors return an alias value of 0. + * This indicates the alias boundary is unknown and may be larger than + * 16 MB. Non-equivalent aliasing is not supported. + * + * Here we assume the maximum alias boundary is 4 MB. + */ +#define TMPALIAS_SIZE_BITS 22 /* 4 MB */ +#define TMPALIAS_MAP_START ((__PAGE_OFFSET) - (2 << TMPALIAS_SIZE_BITS)) #define FIXMAP_SIZE (FIX_BITMAP_COUNT << PAGE_SHIFT) #define FIXMAP_START (TMPALIAS_MAP_START - FIXMAP_SIZE) |