Re: [PATCH 8/8] ARM: dma-mapping: add support for IOMMU mapper

[Hiroshi Doyu <hdoyu@nvidia.com>]

Hi Marek,

On Fri, 9 Dec 2011 17:39:58 +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>
>
> 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>
> ---
>  arch/arm/Kconfig                 |    8 +
>  arch/arm/include/asm/device.h    |    3 +
>  arch/arm/include/asm/dma-iommu.h |   36 +++
>  arch/arm/mm/dma-mapping.c        |  637 +++++++++++++++++++++++++++++++++++++-
>  arch/arm/mm/vmregion.h           |    2 +-
>  5 files changed, 671 insertions(+), 15 deletions(-)
>  create mode 100644 arch/arm/include/asm/dma-iommu.h
>
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 8827c9b..87416fc 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -42,6 +42,14 @@ config ARM
>  config ARM_HAS_SG_CHAIN
>         bool
>
> +config NEED_SG_DMA_LENGTH
> +       bool
> +
> +config ARM_DMA_USE_IOMMU
> +       select NEED_SG_DMA_LENGTH
> +       select ARM_HAS_SG_CHAIN
> +       bool
> +
>  config HAVE_PWM
>         bool
>
> diff --git a/arch/arm/include/asm/device.h b/arch/arm/include/asm/device.h
> index 6e2cb0e..b69c0d3 100644
> --- a/arch/arm/include/asm/device.h
> +++ b/arch/arm/include/asm/device.h
> @@ -14,6 +14,9 @@ struct dev_archdata {
>  #ifdef CONFIG_IOMMU_API
>         void *iommu; /* private IOMMU data */
>  #endif
> +#ifdef CONFIG_ARM_DMA_USE_IOMMU
> +       struct dma_iommu_mapping        *mapping;
> +#endif
>  };
>
>  struct omap_device;
> diff --git a/arch/arm/include/asm/dma-iommu.h b/arch/arm/include/asm/dma-iommu.h
> new file mode 100644
> index 0000000..6668b41
> --- /dev/null
> +++ b/arch/arm/include/asm/dma-iommu.h
> @@ -0,0 +1,36 @@
> +#ifndef ASMARM_DMA_IOMMU_H
> +#define ASMARM_DMA_IOMMU_H
> +
> +#ifdef __KERNEL__
> +
> +#include <linux/mm_types.h>
> +#include <linux/scatterlist.h>
> +#include <linux/dma-debug.h>
> +#include <linux/kmemcheck.h>
> +
> +#include <asm/memory.h>
> +
> +struct dma_iommu_mapping {
> +       /* iommu specific data */
> +       struct iommu_domain     *domain;
> +
> +       void                    *bitmap;
> +       size_t                  bits;
> +       unsigned int            order;
> +       dma_addr_t              base;
> +
> +       spinlock_t              lock;
> +       struct kref             kref;
> +};
> +
> +struct dma_iommu_mapping *
> +arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size,
> +                        int order);
> +
> +void arm_iommu_release_mapping(struct dma_iommu_mapping *mapping);
> +
> +int arm_iommu_attach_device(struct device *dev,
> +                                       struct dma_iommu_mapping *mapping);
> +
> +#endif /* __KERNEL__ */
> +#endif
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 4845c09..7ac5a95 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -27,6 +27,9 @@
>  #include <asm/sizes.h>
>  #include <asm/mach/arch.h>
>
> +#include <linux/iommu.h>
> +#include <asm/dma-iommu.h>
> +
>  #include "mm.h"
>
>  /*
.....
> +
> +static void arm_iommu_unmap_page(struct device *dev, dma_addr_t handle,
> +               size_t size, enum dma_data_direction dir,
> +               struct dma_attrs *attrs)
> +{
> +       struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> +       dma_addr_t iova = handle & PAGE_MASK;
> +       struct page *page = phys_to_page(iommu_iova_to_phys(mapping->domain, iova));
> +       int offset = handle & ~PAGE_MASK;
> +
> +       if (!iova)
> +               return;
> +
> +       if (!arch_is_coherent())
> +               __dma_page_dev_to_cpu(page, offset, size, dir);
> +
> +       iommu_unmap(mapping->domain, iova, size);

Is __free_iova() needed here as below?

	Modified arch/arm/mm/dma-mapping.c
diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 9aa1675..66830b2 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1212,6 +1212,7 @@ static void arm_iommu_unmap_page(struct device *dev, dma_addr_t handle,
		__dma_page_dev_to_cpu(page, offset, size, dir);

	iommu_unmap(mapping->domain, iova, size);
+       __free_iova(mapping, iova, size);
 }