Hi Marek,

On Fri, 9 Dec 2011 17:39:58 +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>

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"

 /*

.....

quoted

+
+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);
 }