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authorMarek Szyprowski <m.szyprowski@samsung.com>2012-06-21 11:48:11 +0200
committerMarek Szyprowski <m.szyprowski@samsung.com>2012-06-25 10:18:52 +0200
commit593f47355467b9ef44293698817e2bdb347e2d11 (patch)
tree2e90c04ac19f11cf8b94c92058d4a0ac0e00401d
parent6b16351acbd415e66ba16bf7d473ece1574cf0bc (diff)
ARM: dma-mapping: fix buffer chunk allocation order
IOMMU-aware dma_alloc_attrs() implementation allocates buffers in power-of-two chunks to improve performance and take advantage of large page mappings provided by some IOMMU hardware. However current code, due to a subtle bug, allocated those chunks in the smallest-to-largest order, what completely killed all the advantages of using larger than page chunks. If a 4KiB chunk has been mapped as a first chunk, the consecutive chunks are not aligned correctly to the power-of-two which match their size and IOMMU drivers were not able to use internal mappings of size other than the 4KiB (largest common denominator of alignment and chunk size). This patch fixes this issue by changing to the correct largest-to-smallest chunk size allocation sequence. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
-rw-r--r--arch/arm/mm/dma-mapping.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index d766e4256b74..4044abcf6f9d 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1067,7 +1067,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size, gfp_t
return NULL;
while (count) {
- int j, order = __ffs(count);
+ int j, order = __fls(count);
pages[i] = alloc_pages(gfp | __GFP_NOWARN, order);
while (!pages[i] && order)