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    ARM: DMA: top-down allocation in DMA coherent region · 459c1517
    Russell King 提交于
    Achieve better usage of the DMA coherent region by doing top-down
    allocation rather than bottom up.  If we ask for a 128kB allocation,
    this will be aligned to 128kB and satisfied from the very bottom
    address.  If we then ask for a 600kB allocation, this will be aligned
    to 1MB, and we will have a 896kB hole.
    
    Performing top-down allocation resolves this by allocating the 128kB
    at the very top, and then the 600kB can come in below it without any
    unnecessary wastage.
    
    This problem was reported by Janusz Krzysztofik, who had 2 x 128kB +
    1 x 640kB allocations which wouldn't fit into 1MB.
    Tested-by: NJanusz Krzysztofik <jkrzyszt@tis.icnet.pl>
    Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
    459c1517
vmregion.c 3.1 KB