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Commit c61e9637 authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

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: default avatarChristoph Hellwig <hch@lst.de>
parent 21f237e4

lib/dma-direct.c

+14 −0
Original line number Diff line number Diff line
@@ -12,6 +12,14 @@ 


#define DIRECT_MAPPING_ERROR		0



/*

 * Most architectures use ZONE_DMA for the first 16 Megabytes, but

 * some use it for entirely different regions:

 */

#ifndef ARCH_ZONE_DMA_BITS

#define ARCH_ZONE_DMA_BITS 24

#endif



static bool

check_addr(struct device *dev, dma_addr_t dma_addr, size_t size,

		const char *caller)
@@ -34,6 +42,12 @@ static void *dma_direct_alloc(struct device *dev, size_t size, 
	int page_order = get_order(size);

	struct page *page = NULL;



	/* GFP_DMA32 and GFP_DMA are no ops without the corresponding zones: */

	if (dev->coherent_dma_mask <= DMA_BIT_MASK(ARCH_ZONE_DMA_BITS))

		gfp |= GFP_DMA;

	if (dev->coherent_dma_mask <= DMA_BIT_MASK(32) && !(gfp & GFP_DMA))

		gfp |= GFP_DMA32;



	/* CMA can be used only in the context which permits sleeping */

	if (gfpflags_allow_blocking(gfp))

		page = dma_alloc_from_contiguous(dev, count, page_order, gfp);