linux-4.4.1/__dma_clean_range()

参照元†

linux-4.4.1/__dma_map_area()

説明†

パス: linux-4.4.1/arch/arm64/mm/cache.S

FIXME: これは何？
- キャッシュの変更された内容（dirty ビットでマークされている内容）を次のキャッシュ（L1 から L2 など）もしくはメインメモリに書き込む
- キャッシュの内容の dirty ビットを消す
- キャッシュの内容は残るので、次に CPU から read したときはキャッシュにヒットする

原文

Invalidation
means to clear it of data, by clearing the valid bit of one or more cache lines.
The cache must always be invalidated after reset as its contents are undefined.
This can also be viewed as a way of making changes in the memory domain outside
the cache visible to the user of the cache.

Cleaning
means writing the contents of cache lines that are marked as dirty,
out to the next level of cache, or to main memory, and clearing the
dirty bits in the cache line.
This makes the contents of the cache line with the next level of the cache or memory system.
This is only applicable for data caches in which a write-back policy is used.
This is also a way of making changes in the cache visible to the user of the outer memory domain,
but is only available for data cache.

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0024a/BABJDBHI.html

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引数†

void *start
void *end

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返り値†

なし

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参考†

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実装†

/*
 *      __dma_clean_range(start, end)
 *      - start   - virtual start address of region
 *      - end     - virtual end address of region
 */
__dma_clean_range:
        dcache_line_size x2, x3

- linux-4.4.1/dcache_line_size()

        sub     x3, x2, #1
        bic     x0, x0, x3
1:
alternative_if_not ARM64_WORKAROUND_CLEAN_CACHE
        dc      cvac, x0
alternative_else
        dc      civac, x0
alternative_endif
        add     x0, x0, x2
        cmp     x0, x1
        b.lo    1b
        dsb     sy
        ret
ENDPROC(__dma_clean_range)

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