isci: simplify dma coherent allocation
Remove the insane infrastructure for preallocating coheren DMA regions, and just allocate the memory where needed. This also gets rid of the aligment adjustments given that Documentation/DMA-API-HOWTO.txt sais: "The cpu return address and the DMA bus master address are both guaranteed to be aligned to the smallest PAGE_SIZE order which is greater than or equal to the requested size. This invariant exists (for example) to guarantee that if you allocate a chunk which is smaller than or equal to 64 kilobytes, the extent of the buffer you receive will not cross a 64K boundary." Signed-off-by: NChristoph Hellwig <hch@lst.de> [djbw: moved allocation from start to init, re-add memset] Signed-off-by: NDan Williams <dan.j.williams@intel.com>
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