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Commit 9d7a224b authored by Christoph Hellwig's avatar Christoph Hellwig
Browse files

dma-direct: always allow dma mask <= physiscal memory size 



This way an architecture with less than 4G of RAM can support dma_mask
smaller than 32-bit without a ZONE_DMA.  Apparently that is a common
case on powerpc.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
parent b4ebe606

kernel/dma/direct.c

+16 −12
Original line number Diff line number Diff line
@@ -284,21 +284,25 @@ int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, int nents, 
	return nents;

}



int dma_direct_supported(struct device *dev, u64 mask)

{

#ifdef CONFIG_ZONE_DMA

	if (mask < phys_to_dma(dev, DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)))

		return 0;

#else

/*

	 * Because 32-bit DMA masks are so common we expect every architecture

	 * to be able to satisfy them - either by not supporting more physical

	 * memory, or by providing a ZONE_DMA32.  If neither is the case, the

	 * architecture needs to use an IOMMU instead of the direct mapping.

 * Because 32-bit DMA masks are so common we expect every architecture to be

 * able to satisfy them - either by not supporting more physical memory, or by

 * providing a ZONE_DMA32.  If neither is the case, the architecture needs to

 * use an IOMMU instead of the direct mapping.

 */

	if (mask < phys_to_dma(dev, DMA_BIT_MASK(32)))

int dma_direct_supported(struct device *dev, u64 mask)

{

	u64 min_mask;



	if (IS_ENABLED(CONFIG_ZONE_DMA))

		min_mask = DMA_BIT_MASK(ARCH_ZONE_DMA_BITS);

	else

		min_mask = DMA_BIT_MASK(32);



	min_mask = min_t(u64, min_mask, (max_pfn - 1) << PAGE_SHIFT);



	if (mask >= phys_to_dma(dev, min_mask))

		return 0;

#endif

	return 1;

}