Commit 8d8d53cf authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by Christoph Hellwig
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dma-mapping: Allow mixing bypass and mapped DMA operation 



At the moment we allow bypassing DMA ops only when we can do this for
the entire RAM. However there are configs with mixed type memory
where we could still allow bypassing IOMMU in most cases;
POWERPC with persistent memory is one example.

This adds an arch hook to determine where bypass can still work and
we invoke direct DMA API. The following patch checks the bus limit
on POWERPC to allow or disallow direct mapping.

This adds a ARCH_HAS_DMA_MAP_DIRECT config option to make the arch_xxxx
hooks no-op by default.

Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 418baf2c

include/linux/dma-map-ops.h

+14 −0
Original line number Diff line number Diff line
@@ -314,6 +314,20 @@ static inline void arch_dma_mark_clean(phys_addr_t paddr, size_t size) 
void *arch_dma_set_uncached(void *addr, size_t size);

void arch_dma_clear_uncached(void *addr, size_t size);



#ifdef CONFIG_ARCH_HAS_DMA_MAP_DIRECT

bool arch_dma_map_page_direct(struct device *dev, phys_addr_t addr);

bool arch_dma_unmap_page_direct(struct device *dev, dma_addr_t dma_handle);

bool arch_dma_map_sg_direct(struct device *dev, struct scatterlist *sg,

		int nents);

bool arch_dma_unmap_sg_direct(struct device *dev, struct scatterlist *sg,

		int nents);

#else

#define arch_dma_map_page_direct(d, a)		(false)

#define arch_dma_unmap_page_direct(d, a)	(false)

#define arch_dma_map_sg_direct(d, s, n)		(false)

#define arch_dma_unmap_sg_direct(d, s, n)	(false)

#endif



#ifdef CONFIG_ARCH_HAS_SETUP_DMA_OPS

void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,

		const struct iommu_ops *iommu, bool coherent);

kernel/dma/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -20,6 +20,10 @@ config DMA_OPS 
config DMA_OPS_BYPASS

	bool



# Lets platform IOMMU driver choose between bypass and IOMMU

config ARCH_HAS_DMA_MAP_DIRECT

	bool



config NEED_SG_DMA_LENGTH

	bool

kernel/dma/mapping.c

+8 −4
Original line number Diff line number Diff line
@@ -149,7 +149,8 @@ dma_addr_t dma_map_page_attrs(struct device *dev, struct page *page, 
	if (WARN_ON_ONCE(!dev->dma_mask))

		return DMA_MAPPING_ERROR;



	if (dma_map_direct(dev, ops))

	if (dma_map_direct(dev, ops) ||

	    arch_dma_map_page_direct(dev, page_to_phys(page) + offset + size))

		addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);

	else

		addr = ops->map_page(dev, page, offset, size, dir, attrs);
@@ -165,7 +166,8 @@ void dma_unmap_page_attrs(struct device *dev, dma_addr_t addr, size_t size, 
	const struct dma_map_ops *ops = get_dma_ops(dev);



	BUG_ON(!valid_dma_direction(dir));

	if (dma_map_direct(dev, ops))

	if (dma_map_direct(dev, ops) ||

	    arch_dma_unmap_page_direct(dev, addr + size))

		dma_direct_unmap_page(dev, addr, size, dir, attrs);

	else if (ops->unmap_page)

		ops->unmap_page(dev, addr, size, dir, attrs);
@@ -188,7 +190,8 @@ int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents, 
	if (WARN_ON_ONCE(!dev->dma_mask))

		return 0;



	if (dma_map_direct(dev, ops))

	if (dma_map_direct(dev, ops) ||

	    arch_dma_map_sg_direct(dev, sg, nents))

		ents = dma_direct_map_sg(dev, sg, nents, dir, attrs);

	else

		ents = ops->map_sg(dev, sg, nents, dir, attrs);
@@ -207,7 +210,8 @@ void dma_unmap_sg_attrs(struct device *dev, struct scatterlist *sg, 


	BUG_ON(!valid_dma_direction(dir));

	debug_dma_unmap_sg(dev, sg, nents, dir);

	if (dma_map_direct(dev, ops))

	if (dma_map_direct(dev, ops) ||

	    arch_dma_unmap_sg_direct(dev, sg, nents))

		dma_direct_unmap_sg(dev, sg, nents, dir, attrs);

	else if (ops->unmap_sg)

		ops->unmap_sg(dev, sg, nents, dir, attrs);

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