From mboxrd@z Thu Jan 1 00:00:00 1970 From: rizhao@nvidia.com (Richard Zhao) Date: Thu, 20 Jun 2013 20:31:00 +0800 Subject: [PATCH] ARM: dma: Drop __GFP_COMP for iommu dma memory allocations Message-ID: <1371731460-15316-1-git-send-email-rizhao@nvidia.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org __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 --- arch/arm/mm/dma-mapping.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c index ef3e0f3..f7efffd 100644 --- a/arch/arm/mm/dma-mapping.c +++ b/arch/arm/mm/dma-mapping.c @@ -1314,6 +1314,15 @@ 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; -- 1.7.9.5