[PATCH v4] arm DMA: Fix allocation from CMA for coherent DMA
From: catalin.marinas@arm.com (Catalin Marinas)
Date: 2015-06-30 11:05:32
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On Mon, Jun 29, 2015 at 07:10:45PM +0200, Lorenzo Nava wrote:
This patch allows the use of CMA for DMA coherent memory allocation. At the moment if the input parameter "is_coherent" is set to true the allocation is not made using the CMA, which I think is not the desired behaviour. Signed-off-by: Lorenzo Nava <redacted>
It's nice to have a proper email address here.
quoted hunk ↗ jump to hunk
@@ -680,9 +684,14 @@ void *arm_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, static void *arm_coherent_dma_alloc(struct device *dev, size_t size, dma_addr_t *handle, gfp_t gfp, struct dma_attrs *attrs) { - pgprot_t prot = __get_dma_pgprot(attrs, PAGE_KERNEL); + pgprot_t prot; void *memory; + if (attrs == NULL) + prot = PAGE_KERNEL; + else + prot = __get_dma_pgprot(attrs, PAGE_KERNEL); + if (dma_alloc_from_coherent(dev, size, handle, &memory)) return memory;
We have a slight inconsistency with commit 55af8a91640d (ARM: 8387/1: arm/mm/dma-mapping.c: Add arm_coherent_dma_mmap) where the attrs are not honoured for the coherent ops. That is, DMA_ATTRS_WRITE_COMBINE doesn't have any effect for mmap but with your patch it still has an effect on alloc. I think we could just ignore it, the WRITE_COMBINE attr is a hint that the arch may or may not implement and I haven't seen it used with coherent mappings. So in this case just pass PAGE_KERNEL to __dma_alloc() directly without calling __get_dma_pgprot(). (it also looks like commit 55af8a91640d left an unused attrs argument for __arm_dma_mmap that can be removed as well) Apart from the above, you can add: Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>