diff options
| -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 67874b82a4e..4e89112b57e 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 2163af4b31b..6e2511561c3 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; |