[RFC 2/2] ARM: dma-mapping: add support for DMA_ATTR_FORCE_CONTIGUOUS attribute

[Marek Szyprowski]

This patch adds support for DMA_ATTR_FORCE_CONTIGUOUS attribute for
dma_alloc_attrs() in IOMMU-aware implementation. For allocating physically
contiguous buffers Contiguous Memory Allocator is used.

Signed-off-by: Marek Szyprowski <m.szyprow...@samsung.com>
---
 arch/arm/mm/dma-mapping.c |   41 +++++++++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 8 deletions(-)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 477a2d2..583a302 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1036,7 +1036,8 @@ static inline void __free_iova(struct dma_iommu_mapping 
*mapping,
        spin_unlock_irqrestore(&mapping->lock, flags);
 }
 
-static struct page **__iommu_alloc_buffer(struct device *dev, size_t size, 
gfp_t gfp)
+static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
+                                         gfp_t gfp, struct dma_attrs *attrs)
 {
        struct page **pages;
        int count = size >> PAGE_SHIFT;
@@ -1050,6 +1051,23 @@ static struct page **__iommu_alloc_buffer(struct device 
*dev, size_t size, gfp_t
        if (!pages)
                return NULL;
 
+       if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs))
+       {
+               unsigned long order = get_order(size);
+               struct page *page;
+
+               page = dma_alloc_from_contiguous(dev, count, order);
+               if (!page)
+                       goto error;
+
+               __dma_clear_buffer(page, size);
+
+               for (i = 0; i < count; i++)
+                       pages[i] = page + i;
+
+               return pages;
+       }
+
        while (count) {
                int j, order = __fls(count);
 
@@ -1083,14 +1101,21 @@ error:
        return NULL;
 }
 
-static int __iommu_free_buffer(struct device *dev, struct page **pages, size_t 
size)
+static int __iommu_free_buffer(struct device *dev, struct page **pages,
+                              size_t size, struct dma_attrs *attrs)
 {
        int count = size >> PAGE_SHIFT;
        int array_size = count * sizeof(struct page *);
        int i;
-       for (i = 0; i < count; i++)
-               if (pages[i])
-                       __free_pages(pages[i], 0);
+
+       if (dma_get_attr(DMA_ATTR_FORCE_CONTIGUOUS, attrs)) {
+               dma_release_from_contiguous(dev, pages[0], count);
+       } else {
+               for (i = 0; i < count; i++)
+                       if (pages[i])
+                               __free_pages(pages[i], 0);
+       }
+
        if (array_size <= PAGE_SIZE)
                kfree(pages);
        else
@@ -1252,7 +1277,7 @@ static void *arm_iommu_alloc_attrs(struct device *dev, 
size_t size,
        if (gfp & GFP_ATOMIC)
                return __iommu_alloc_atomic(dev, size, handle);
 
-       pages = __iommu_alloc_buffer(dev, size, gfp);
+       pages = __iommu_alloc_buffer(dev, size, gfp, attrs);
        if (!pages)
                return NULL;
 
@@ -1273,7 +1298,7 @@ static void *arm_iommu_alloc_attrs(struct device *dev, 
size_t size,
 err_mapping:
        __iommu_remove_mapping(dev, *handle, size);
 err_buffer:
-       __iommu_free_buffer(dev, pages, size);
+       __iommu_free_buffer(dev, pages, size, attrs);
        return NULL;
 }
 
@@ -1329,7 +1354,7 @@ void arm_iommu_free_attrs(struct device *dev, size_t 
size, void *cpu_addr,
        }
 
        __iommu_remove_mapping(dev, handle, size);
-       __iommu_free_buffer(dev, pages, size);
+       __iommu_free_buffer(dev, pages, size, attrs);
 }
 
 static int arm_iommu_get_sgtable(struct device *dev, struct sg_table *sgt,
-- 
1.7.9.5

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