ARM: dma-mapping: Always pass proper prot flags to iommu_map()

... otherwise it is impossible for the low level iommu driver to
figure out which pte flags should be used.

In __map_sg_chunk we can derive the flags from dma_data_direction.

In __iommu_create_mapping we should treat the memory like
DMA_BIDIRECTIONAL and pass both IOMMU_READ and IOMMU_WRITE to
iommu_map.
__iommu_create_mapping is used during dma_alloc_coherent (via
arm_iommu_alloc_attrs).  AFAIK dma_alloc_coherent is responsible for
allocation _and_ mapping.  I think this implies that access to the
mapped pages should be allowed.

Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Andreas Herrmann <andreas.herrmann@calxeda.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

arch/arm/mm/dma-mapping.c

@@ -1232,7 +1232,8 @@ __iommu_create_mapping(struct device *dev, struct page **pages, size_t size)
 				break;
 
 		len = (j - i) << PAGE_SHIFT;
-		ret = iommu_map(mapping->domain, iova, phys, len, 0);
+		ret = iommu_map(mapping->domain, iova, phys, len,
+				IOMMU_READ|IOMMU_WRITE);
 		if (ret < 0)
 			goto fail;
 		iova += len;
@@ -1431,6 +1432,27 @@ static int arm_iommu_get_sgtable(struct device *dev, struct sg_table *sgt,
 					 GFP_KERNEL);
 }
 
+static int __dma_direction_to_prot(enum dma_data_direction dir)
+{
+	int prot;
+
+	switch (dir) {
+	case DMA_BIDIRECTIONAL:
+		prot = IOMMU_READ | IOMMU_WRITE;
+		break;
+	case DMA_TO_DEVICE:
+		prot = IOMMU_READ;
+		break;
+	case DMA_FROM_DEVICE:
+		prot = IOMMU_WRITE;
+		break;
+	default:
+		prot = 0;
+	}
+
+	return prot;
+}
+
 /*
  * Map a part of the scatter-gather list into contiguous io address space
  */
@@ -1444,6 +1466,7 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
 	int ret = 0;
 	unsigned int count;
 	struct scatterlist *s;
+	int prot;
 
 	size = PAGE_ALIGN(size);
 	*handle = DMA_ERROR_CODE;
@@ -1460,7 +1483,9 @@ static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
 			!dma_get_attr(DMA_ATTR_SKIP_CPU_SYNC, attrs))
 			__dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir);
 
-		ret = iommu_map(mapping->domain, iova, phys, len, 0);
+		prot = __dma_direction_to_prot(dir);
+
+		ret = iommu_map(mapping->domain, iova, phys, len, prot);
 		if (ret < 0)
 			goto fail;
 		count += len >> PAGE_SHIFT;
@@ -1665,19 +1690,7 @@ static dma_addr_t arm_coherent_iommu_map_page(struct device *dev, struct page *p
 	if (dma_addr == DMA_ERROR_CODE)
 		return dma_addr;
 
-	switch (dir) {
-	case DMA_BIDIRECTIONAL:
-		prot = IOMMU_READ | IOMMU_WRITE;
-		break;
-	case DMA_TO_DEVICE:
-		prot = IOMMU_READ;
-		break;
-	case DMA_FROM_DEVICE:
-		prot = IOMMU_WRITE;
-		break;
-	default:
-		prot = 0;
-	}
+	prot = __dma_direction_to_prot(dir);
 
 	ret = iommu_map(mapping->domain, dma_addr, page_to_phys(page), len, prot);
 	if (ret < 0)