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Commit fe3e2172 authored by Marek Szyprowski's avatar Marek Szyprowski Committed by Greg Kroah-Hartman
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dma-mapping: add generic helpers for mapping sgtable objects 



[ Upstream commit d9d200bcebc1f6e56f0178cbb8db9953e8cc9a11 ]

struct sg_table is a common structure used for describing a memory
buffer. It consists of a scatterlist with memory pages and DMA addresses
(sgl entry), as well as the number of scatterlist entries: CPU pages
(orig_nents entry) and DMA mapped pages (nents entry).

It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg
function.

To avoid such issues, let's introduce a common wrappers operating
directly on the struct sg_table objects, which take care of the proper
use of the nents and orig_nents entries.

Signed-off-by: default avatarMarek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: default avatarRobin Murphy <robin.murphy@arm.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Stable-dep-of: d37c120b7312 ("drm/etnaviv: don't truncate physical page address")
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 64121e2a

include/linux/dma-mapping.h

+80 −0
Original line number Diff line number Diff line
@@ -612,6 +612,86 @@ static inline void dma_sync_single_range_for_device(struct device *dev, 
	return dma_sync_single_for_device(dev, addr + offset, size, dir);

}



/**

 * dma_map_sgtable - Map the given buffer for DMA

 * @dev:	The device for which to perform the DMA operation

 * @sgt:	The sg_table object describing the buffer

 * @dir:	DMA direction

 * @attrs:	Optional DMA attributes for the map operation

 *

 * Maps a buffer described by a scatterlist stored in the given sg_table

 * object for the @dir DMA operation by the @dev device. After success the

 * ownership for the buffer is transferred to the DMA domain.  One has to

 * call dma_sync_sgtable_for_cpu() or dma_unmap_sgtable() to move the

 * ownership of the buffer back to the CPU domain before touching the

 * buffer by the CPU.

 *

 * Returns 0 on success or -EINVAL on error during mapping the buffer.

 */

static inline int dma_map_sgtable(struct device *dev, struct sg_table *sgt,

		enum dma_data_direction dir, unsigned long attrs)

{

	int nents;



	nents = dma_map_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs);

	if (nents <= 0)

		return -EINVAL;

	sgt->nents = nents;

	return 0;

}



/**

 * dma_unmap_sgtable - Unmap the given buffer for DMA

 * @dev:	The device for which to perform the DMA operation

 * @sgt:	The sg_table object describing the buffer

 * @dir:	DMA direction

 * @attrs:	Optional DMA attributes for the unmap operation

 *

 * Unmaps a buffer described by a scatterlist stored in the given sg_table

 * object for the @dir DMA operation by the @dev device. After this function

 * the ownership of the buffer is transferred back to the CPU domain.

 */

static inline void dma_unmap_sgtable(struct device *dev, struct sg_table *sgt,

		enum dma_data_direction dir, unsigned long attrs)

{

	dma_unmap_sg_attrs(dev, sgt->sgl, sgt->orig_nents, dir, attrs);

}



/**

 * dma_sync_sgtable_for_cpu - Synchronize the given buffer for CPU access

 * @dev:	The device for which to perform the DMA operation

 * @sgt:	The sg_table object describing the buffer

 * @dir:	DMA direction

 *

 * Performs the needed cache synchronization and moves the ownership of the

 * buffer back to the CPU domain, so it is safe to perform any access to it

 * by the CPU. Before doing any further DMA operations, one has to transfer

 * the ownership of the buffer back to the DMA domain by calling the

 * dma_sync_sgtable_for_device().

 */

static inline void dma_sync_sgtable_for_cpu(struct device *dev,

		struct sg_table *sgt, enum dma_data_direction dir)

{

	dma_sync_sg_for_cpu(dev, sgt->sgl, sgt->orig_nents, dir);

}



/**

 * dma_sync_sgtable_for_device - Synchronize the given buffer for DMA

 * @dev:	The device for which to perform the DMA operation

 * @sgt:	The sg_table object describing the buffer

 * @dir:	DMA direction

 *

 * Performs the needed cache synchronization and moves the ownership of the

 * buffer back to the DMA domain, so it is safe to perform the DMA operation.

 * Once finished, one has to call dma_sync_sgtable_for_cpu() or

 * dma_unmap_sgtable().

 */

static inline void dma_sync_sgtable_for_device(struct device *dev,

		struct sg_table *sgt, enum dma_data_direction dir)

{

	dma_sync_sg_for_device(dev, sgt->sgl, sgt->orig_nents, dir);

}



#define dma_map_single(d, a, s, r) dma_map_single_attrs(d, a, s, r, 0)

#define dma_unmap_single(d, a, s, r) dma_unmap_single_attrs(d, a, s, r, 0)

#define dma_map_sg(d, s, n, r) dma_map_sg_attrs(d, s, n, r, 0)