Merge branch 'for-v3.9' of git://git.linaro.org/people/mszyprowski/linux-dma-mapping

[~andy/linux] / arch / arm / Kconfig

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index a955d89ed83642cd5b5b62d7954edd8241637730..6ec8eb3149ead02ed81c9fdafa26cf86d9bca2b1 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -77,6 +77,27 @@ config ARM_DMA_USE_IOMMU
        select ARM_HAS_SG_CHAIN
        select NEED_SG_DMA_LENGTH
 
+if ARM_DMA_USE_IOMMU
+
+config ARM_DMA_IOMMU_ALIGNMENT
+       int "Maximum PAGE_SIZE order of alignment for DMA IOMMU buffers"
+       range 4 9
+       default 8
+       help
+         DMA mapping framework by default aligns all buffers to the smallest
+         PAGE_SIZE order which is greater than or equal to the requested buffer
+         size. This works well for buffers up to a few hundreds kilobytes, but
+         for larger buffers it just a waste of address space. Drivers which has
+         relatively small addressing window (like 64Mib) might run out of
+         virtual space with just a few allocations.
+
+         With this parameter you can specify the maximum PAGE_SIZE order for
+         DMA IOMMU buffers. Larger buffers will be aligned only to this
+         specified order. The order is expressed as a power of two multiplied
+         by the PAGE_SIZE.
+
+endif
+
 config HAVE_PWM
        bool