ARM: dma: Drop __GFP_COMP for iommu dma memory allocations

__iommu_alloc_buffer wants to split pages after allocation in order to
reduce the memory footprint. This does not work well with __GFP_COMP
pages, so drop this flag before allocation

One failure example is snd_malloc_dev_pages call dma_alloc_coherent with
__GFP_COMP.

Signed-off-by: Richard Zhao <rizhao@nvidia.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 97926b1..22c7d7e 100644 (file)
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -1328,6 +1328,15 @@ static void *arm_iommu_alloc_attrs(struct device *dev, size_t size,
        if (gfp & GFP_ATOMIC)
                return __iommu_alloc_atomic(dev, size, handle);
 
+       /*
+        * Following is a work-around (a.k.a. hack) to prevent pages
+        * with __GFP_COMP being passed to split_page() which cannot
+        * handle them.  The real problem is that this flag probably
+        * should be 0 on ARM as it is not supported on this
+        * platform; see CONFIG_HUGETLBFS.
+        */
+       gfp &= ~(__GFP_COMP);
+
        pages = __iommu_alloc_buffer(dev, size, gfp, attrs);
        if (!pages)
                return NULL;