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Commit 60460abf authored by Seung-Woo Kim's avatar Seung-Woo Kim Committed by Marek Szyprowski
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ARM: dma-mapping: Add maximum alignment order for dma iommu buffers 



Alignment order for a dma iommu buffer is set by buffer size. For
large buffer, it is a waste of iommu address space. So configurable
parameter to limit maximum alignment order can reduce the waste.

Signed-off-by: default avatarSeung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: default avatarKyungmin.park <kyungmin.park@samsung.com>
Signed-off-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
parent f8669bef

arch/arm/Kconfig

+21 −0
Original line number Diff line number Diff line
@@ -75,6 +75,27 @@ 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

arch/arm/mm/dma-mapping.c

+3 −0
Original line number Diff line number Diff line
@@ -1029,6 +1029,9 @@ static inline dma_addr_t __alloc_iova(struct dma_iommu_mapping *mapping, 
	unsigned int count, start;

	unsigned long flags;



	if (order > CONFIG_ARM_DMA_IOMMU_ALIGNMENT)

		order = CONFIG_ARM_DMA_IOMMU_ALIGNMENT;



	count = ((PAGE_ALIGN(size) >> PAGE_SHIFT) +

		 (1 << mapping->order) - 1) >> mapping->order;