Hello,
On Thursday, March 29, 2012 9:19 AM Hiroshi Doyu wrote:
On Wed, 29 Feb 2012 16:04:22 +0100 Marek Szyprowski m.szyprowski@samsung.com wrote:
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 vdumpa@nvidia.com and Andrzej Pietrasiewicz andrzej.p@samsung.com
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com Signed-off-by: Kyungmin Park kyungmin.park@samsung.com Reviewed-by: Konrad Rzeszutek Wilk konrad.wilk@oracle.com
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>
+/*
- 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).
From e8bcc3cdac5375b5d7f5ac5b3f716a11c1008f38 Mon Sep 17 00:00:00 2001 From: Hiroshi DOYU hdoyu@nvidia.com 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 hdoyu@nvidia.com
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