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>
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index e47c63b..9c4dd3d 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -204,6 +204,14 @@
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
--------------------------------
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 48ebe829..de41a4f 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -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,
diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 1b96616..72c825c 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -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);
