[PATCHv7 9/9] ARM: dma-mapping: add support for IOMMU mapper
From: m.szyprowski@samsung.com (Marek Szyprowski)
Date: 2012-03-29 08:00:20
Also in:
linux-arch, linux-iommu, linux-mm, linux-samsung-soc
Hello, On Thursday, March 29, 2012 9:19 AM Hiroshi Doyu wrote:
On Wed, 29 Feb 2012 16:04:22 +0100 Marek Szyprowski [off-list ref] wrote:quoted
This patch add a complete implementation of DMA-mapping API for devices that have IOMMU support. All DMA-mapping calls are supported. This patch contains some of the code kindly provided by Krishna Reddy [off-list ref] and Andrzej Pietrasiewicz [off-list ref] Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> Reviewed-by: Konrad Rzeszutek Wilk <redacted> --- arch/arm/Kconfig | 8 + arch/arm/include/asm/device.h | 3 + arch/arm/include/asm/dma-iommu.h | 34 ++ arch/arm/mm/dma-mapping.c | 726 +++++++++++++++++++++++++++++++++++++- arch/arm/mm/vmregion.h | 2 +- 5 files changed, 758 insertions(+), 15 deletions(-) create mode 100644 arch/arm/include/asm/dma-iommu.h<snip>quoted
+/* + * Map a part of the scatter-gather list into contiguous io address space + */ +static int __map_sg_chunk(struct device *dev, struct scatterlist *sg, + size_t size, dma_addr_t *handle, + enum dma_data_direction dir) +{ + struct dma_iommu_mapping *mapping = dev->archdata.mapping; + dma_addr_t iova, iova_base; + int ret = 0; + unsigned int count; + struct scatterlist *s; + + size = PAGE_ALIGN(size); + *handle = ARM_DMA_ERROR; + + iova_base = iova = __alloc_iova(mapping, size); + if (iova == ARM_DMA_ERROR) + return -ENOMEM; + + for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s)) + { + phys_addr_t phys = page_to_phys(sg_page(s)); + unsigned int len = PAGE_ALIGN(s->offset + s->length); + + if (!arch_is_coherent()) + __dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir); + + ret = iommu_map(mapping->domain, iova, phys, len, 0); + if (ret < 0) + goto fail; + count += len >> PAGE_SHIFT; + iova += len; + } + *handle = iova_base; + + return 0; +fail: + iommu_unmap(mapping->domain, iova_base, count * PAGE_SIZE); + __free_iova(mapping, iova_base, size); + return ret; +}Do we need to set dma_address as below?
Nope, this one is not correct. Please check the arm_iommu_map_sg() function. It calls __map_sg_chunk() and gives it &dma->dma_address as one of the arguments, so the dma address is correctly stored in the scatter list. Please note that scatterlist is really non-trivial structure and information about physical memory pages/chunks is disjoint from the information about dma address space chunks, although both are stored on the same list. In arm_iommu_map_sg() 's' pointer is used for physical memory chunks and 'dma' pointer is used for dma address space chunks. The number of dma address space chunks (returned by arm_iommu_map_sq) can be lower than the number of physical memory chunks (given as nents argument). In case of IOMMU you usually construct the scatter list in such a way, that you get only one dma address chunk (so in fact you get a buffer mapped contiguously in virtual io address space).
quoted hunk ↗ jump to hunk
From e8bcc3cdac5375b5d7f5ac5b3f716a11c1008f38 Mon Sep 17 00:00:00 2001 From: Hiroshi DOYU <redacted> Date: Thu, 29 Mar 2012 09:59:04 +0300 Subject: [PATCH 1/1] ARM: dma-mapping: Fix dma_address in sglist s->dma_address wasn't set at mapping. Signed-off-by: Hiroshi DOYU <redacted> --- arch/arm/mm/dma-mapping.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-)diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index 3347c37..11a9d65 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c@@ -1111,6 +1111,8 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg, ret = iommu_map(mapping->domain, iova, phys, len, 0); if (ret < 0) goto fail; + s->dma_address = iova; + count += len >> PAGE_SHIFT; iova += len; }
The above patch is not needed at all. Best regards -- Marek Szyprowski Samsung Poland R&D Center