[Linaro-mm-sig] [RFC 2/2] ARM: initial proof-of-concept IOMMU mapper for DMA-mapping
From: Ramirez Luna, Omar <hidden>
Date: 2011-07-14 18:32:41
Also in:
linux-mm
Hi Marek,
Add initial proof of concept implementation of DMA-mapping API for devices that have IOMMU support. Right now only dma_alloc_coherent, dma_free_coherent and dma_mmap_coherent functions are supported. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com> ---
...
quoted hunk
diff --git a/arch/arm/include/asm/dma-iommu.h b/arch/arm/include/asm/dma-iommu.h new file mode 100644 index 0000000..c246ff3 --- /dev/null +++ b/arch/arm/include/asm/dma-iommu.h
...
+int __init arm_iommu_assign_device(struct device *dev, dma_addr_t base, dma_addr_t size);
__init causes a panic if the iommu is assigned after boot. In OMAP3 the iommu driver controls isp and dsp address spaces, it is loaded until any of those 2 drivers is needed.
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diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index f8c6972..b6397c1 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c
...
+static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
+ ? ? ? ? ? dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs)
+{
+ ? ? ? struct dma_iommu_mapping *mapping = dev->archdata.mapping;
+ ? ? ? struct page **pages;
+ ? ? ? void *addr = NULL;
+ ? ? ? pgprot_t prot;
+
+ ? ? ? if (dma_get_attr(DMA_ATTR_WRITE_COMBINE, attrs))
+ ? ? ? ? ? ? ? prot = pgprot_writecombine(pgprot_kernel);
+ ? ? ? else
+ ? ? ? ? ? ? ? prot = pgprot_dmacoherent(pgprot_kernel);
+
+ ? ? ? arm_iommu_init(dev);I found useful to call arm_iommu_init inside arm_iommu_assign_device instead. So, then gen_pool is created only once without the mapping->pool check, instead of relying on the call to ...alloc_attrs, which in my case I never use because I'm implementing iommu_map|unmap_sg functions to see how it goes with the dma mapping. Regards, Omar