| From dhobsong@igel.co.jp Mon Oct 29 00:53:48 2012 |
| From: Damian Hobson-Garcia <dhobsong@igel.co.jp> |
| Date: Mon, 29 Oct 2012 16:51:05 +0900 |
| Subject: [PATCH v2 48/58] ARM: dma-mapping: fix buffer chunk allocation order |
| To: greg@kroah.com, laurent.pinchart@ideasonboard.com, horms@verge.net.au |
| Cc: ltsi-dev@lists.linuxfoundation.org, dhobsong@igel.co.jp |
| Message-ID: <1351497075-32717-49-git-send-email-dhobsong@igel.co.jp> |
| |
| |
| From: Marek Szyprowski <m.szyprowski@samsung.com> |
| |
| 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> |
| (cherry picked from commit 593f47355467b9ef44293698817e2bdb347e2d11) |
| |
| Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp> |
| --- |
| arch/arm/mm/dma-mapping.c | 2 +- |
| 1 file changed, 1 insertion(+), 1 deletion(-) |
| |
| --- a/arch/arm/mm/dma-mapping.c |
| +++ b/arch/arm/mm/dma-mapping.c |
| @@ -942,7 +942,7 @@ static struct page **__iommu_alloc_buffe |
| 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) |
