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dma-mapping: introduce dma_get_merge_boundary() 

This patch adds a new DMA API "dma_get_merge_boundary". This function
returns the DMA merge boundary if the DMA layer can merge the segments.
This patch also adds the implementation for a new dma_map_ops pointer.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Christoph Hellwig <hch@lst.de>
This commit is contained in:
Yoshihiro Shimoda 2019-08-28 21:35:40 +09:00 committed by Christoph Hellwig
parent 38c38cb732
commit 6ba99411b8
3 changed files with 25 additions and 0 deletions
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8
Documentation/DMA-API.txt
View File

@ -204,6 +204,14 @@ Returns the maximum size of a mapping for the device. The size parameter
of the mapping functions like dma_map_single(), dma_map_page() and
others should not be larger than the returned value.
::
unsigned long
dma_get_merge_boundary(struct device *dev);
Returns the DMA merge boundary. If the device cannot merge any the DMA address
segments, the function returns 0.
Part Id - Streaming DMA mappings
--------------------------------

6
include/linux/dma-mapping.h
View File

@ -131,6 +131,7 @@ struct dma_map_ops {
int (*dma_supported)(struct device *dev, u64 mask);
u64 (*get_required_mask)(struct device *dev);
size_t (*max_mapping_size)(struct device *dev);
unsigned long (*get_merge_boundary)(struct device *dev);
};
#define DMA_MAPPING_ERROR (~(dma_addr_t)0)
@ -467,6 +468,7 @@ int dma_set_mask(struct device *dev, u64 mask);
int dma_set_coherent_mask(struct device *dev, u64 mask);
u64 dma_get_required_mask(struct device *dev);
size_t dma_max_mapping_size(struct device *dev);
unsigned long dma_get_merge_boundary(struct device *dev);
#else /* CONFIG_HAS_DMA */
static inline dma_addr_t dma_map_page_attrs(struct device *dev,
struct page *page, size_t offset, size_t size,
@ -572,6 +574,10 @@ static inline size_t dma_max_mapping_size(struct device *dev)
{
return 0;
}
static inline unsigned long dma_get_merge_boundary(struct device *dev)
{
return 0;
}
#endif /* CONFIG_HAS_DMA */
static inline dma_addr_t dma_map_single_attrs(struct device *dev, void *ptr,

11
kernel/dma/mapping.c
View File

@ -407,3 +407,14 @@ size_t dma_max_mapping_size(struct device *dev)
return size;
}
EXPORT_SYMBOL_GPL(dma_max_mapping_size);
unsigned long dma_get_merge_boundary(struct device *dev)
{
const struct dma_map_ops *ops = get_dma_ops(dev);
if (!ops || !ops->get_merge_boundary)
return 0; /* can't merge */
return ops->get_merge_boundary(dev);
}
EXPORT_SYMBOL_GPL(dma_get_merge_boundary);