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@xxxxxxxxxxx> 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@xxxxxxxxxx> and Andrzej Pietrasiewicz <andrzej.p@xxxxxxxxxxx>
> >
> > Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> > Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
> > Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > ---
> > 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@xxxxxxxxxx>
> 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@xxxxxxxxxx>
> ---
> 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
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