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| author | Vineet Gupta <vgupta@synopsys.com> | 2016-02-10 06:52:07 +0530 |
|---|---|---|
| committer | Vineet Gupta <vgupta@synopsys.com> | 2016-02-12 12:10:25 +0530 |
| commit | 37eda9df5bd8444263418495632ea6ec750f03f9 (patch) | |
| tree | 2336e3a18d082fda05e907158b61fa34e2bcde7c /arch/arc/include | |
| parent | dec2b2849cfccf09822d6ce3f9bc84b8c8611152 (diff) | |
| download | blackbird-obmc-linux-37eda9df5bd8444263418495632ea6ec750f03f9.tar.gz blackbird-obmc-linux-37eda9df5bd8444263418495632ea6ec750f03f9.zip | |
ARC: mm: Introduce explicit super page size support
MMUv4 supports 2 concurrent page sizes: Normal and Super [4K to 16M]
So far Linux supported a single super page size for a given Normal page,
depending on the software page walking address split.
e.g. we had 11:8:13 address split for 8K page, which meant super page
was 2 ^(8+13) = 2M (given that THP size has to be PMD_SHIFT)
Now we turn this around, by allowing multiple Super Pages in Kconfig
(currently 2M and 16M only) and forcing page walker address split to
PGDIR_SHIFT and PAGE_SHIFT
For configs without Super page, things are same as before and
PGDIR_SHIFT can be hacked to get non default address split
The motivation for this change is a customer who needs 16M super page
and a 8K Normal page combo.
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Diffstat (limited to 'arch/arc/include')
| -rw-r--r-- | arch/arc/include/asm/pgtable.h | 45 |
1 files changed, 26 insertions, 19 deletions
diff --git a/arch/arc/include/asm/pgtable.h b/arch/arc/include/asm/pgtable.h index 57af2f05ae84..d426d4215513 100644 --- a/arch/arc/include/asm/pgtable.h +++ b/arch/arc/include/asm/pgtable.h @@ -179,37 +179,44 @@ #define __S111 PAGE_U_X_W_R /**************************************************************** - * Page Table Lookup split + * 2 tier (PGD:PTE) software page walker * - * We implement 2 tier paging and since this is all software, we are free - * to customize the span of a PGD / PTE entry to suit us - * - * 32 bit virtual address + * [31] 32 bit virtual address [0] * ------------------------------------------------------- - * | BITS_FOR_PGD | BITS_FOR_PTE | BITS_IN_PAGE | + * | | <------------ PGDIR_SHIFT ----------> | + * | | | + * | BITS_FOR_PGD | BITS_FOR_PTE | <-- PAGE_SHIFT --> | * ------------------------------------------------------- * | | | * | | --> off in page frame - * | | * | ---> index into Page Table - * | * ----> index into Page Directory + * + * In a single page size configuration, only PAGE_SHIFT is fixed + * So both PGD and PTE sizing can be tweaked + * e.g. 8K page (PAGE_SHIFT 13) can have + * - PGDIR_SHIFT 21 -> 11:8:13 address split + * - PGDIR_SHIFT 24 -> 8:11:13 address split + * + * If Super Page is configured, PGDIR_SHIFT becomes fixed too, + * so the sizing flexibility is gone. */ -#define BITS_IN_PAGE PAGE_SHIFT - -/* Optimal Sizing of Pg Tbl - based on MMU page size */ -#if defined(CONFIG_ARC_PAGE_SIZE_8K) -#define BITS_FOR_PTE 8 /* 11:8:13 */ -#elif defined(CONFIG_ARC_PAGE_SIZE_16K) -#define BITS_FOR_PTE 8 /* 10:8:14 */ -#elif defined(CONFIG_ARC_PAGE_SIZE_4K) -#define BITS_FOR_PTE 9 /* 11:9:12 */ +#if defined(CONFIG_ARC_HUGEPAGE_16M) +#define PGDIR_SHIFT 24 +#elif defined(CONFIG_ARC_HUGEPAGE_2M) +#define PGDIR_SHIFT 21 +#else +/* + * Only Normal page support so "hackable" (see comment above) + * Default value provides 11:8:13 (8K), 11:9:12 (4K) + */ +#define PGDIR_SHIFT 21 #endif -#define BITS_FOR_PGD (32 - BITS_FOR_PTE - BITS_IN_PAGE) +#define BITS_FOR_PTE (PGDIR_SHIFT - PAGE_SHIFT) +#define BITS_FOR_PGD (32 - PGDIR_SHIFT) -#define PGDIR_SHIFT (32 - BITS_FOR_PGD) #define PGDIR_SIZE (1UL << PGDIR_SHIFT) /* vaddr span, not PDG sz */ #define PGDIR_MASK (~(PGDIR_SIZE-1)) |
