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dma-direct: add support for allocation from ZONE_DMA and ZONE_DMA32
This allows to dip into zones for lower memory if they are available. If one of the zones is not available the corresponding GFP_* flag will evaluate to 0 so they won't change anything. We provide an arch tunable for those architectures that do not use GFP_DMA for the lowest 24-bits, given that there are a few. Roughly based on the x86 code. Signed-off-by: Christoph Hellwig <hch@lst.de>
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@ -12,6 +12,14 @@
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#define DIRECT_MAPPING_ERROR 0
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/*
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* Most architectures use ZONE_DMA for the first 16 Megabytes, but
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* some use it for entirely different regions:
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*/
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#ifndef ARCH_ZONE_DMA_BITS
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#define ARCH_ZONE_DMA_BITS 24
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#endif
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static bool
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check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,
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const char *caller)
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@ -34,6 +42,12 @@ static void *dma_direct_alloc(struct device *dev, size_t size,
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int page_order = get_order(size);
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struct page *page = NULL;
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/* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */
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if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))
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gfp |= GFP_DMA;
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if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))
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gfp |= GFP_DMA32;
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/* CMA can be used only in the context which permits sleeping */
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if (gfpflags_allow_blocking(gfp))
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page = dma_alloc_from_contiguous(dev, count, page_order, gfp);
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