diff options
| author | Seung-Woo Kim <sw0312.kim@samsung.com> | 2013-02-06 05:21:14 +0100 |
|---|---|---|
| committer | Marek Szyprowski <m.szyprowski@samsung.com> | 2013-02-25 15:30:43 +0100 |
| commit | 60460abffc71523d65774f43ce1252972eeb0629 (patch) | |
| tree | 07c55cb6ad9d203c95a2fae8a2de4e0ea25e9a3e /arch | |
| parent | ARM: dma-mapping: use himem for DMA buffers for IOMMU-mapped devices (diff) | |
| download | linux-60460abffc71523d65774f43ce1252972eeb0629.tar.xz linux-60460abffc71523d65774f43ce1252972eeb0629.zip | |
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: Seung-Woo Kim <sw0312.kim@samsung.com>
Signed-off-by: Kyungmin.park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/arm/Kconfig | 21 | ||||
| -rw-r--r-- | arch/arm/mm/dma-mapping.c | 3 |
2 files changed, 24 insertions, 0 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 67874b82a4ed..4e89112b57e0 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -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 diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 2163af4b31b8..6e2511561c3e 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -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; |