[PATCH 2/3] dma: Introduce dma_max_mapping_size()

Joerg Roedel
2019-01-15T13:23:04Z

From: Joerg Roedel <jroedel@suse.de>

The function returns the maximum size that can be mapped
using DMA-API functions. The patch also adds the
implementation for direct DMA and a new dma_map_ops pointer
so that other implementations can expose their limit.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
include/linux/dma-mapping.h | 16 ++++++++++++++++
kernel/dma/direct.c | 10 ++++++++++
2 files changed, 26 insertions(+)

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index f6ded992c183..a3ca8a71a704 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -130,6 +130,7 @@ struct dma_map_ops {
enum dma_data_direction direction);
int (*dma_supported)(struct device *dev, u64 mask);
u64 (*get_required_mask)(struct device *dev);
+ size_t (*max_mapping_size)(struct device *dev);
};

#define DMA_MAPPING_ERROR (~(dma_addr_t)0)
@@ -257,6 +258,8 @@ static inline void dma_direct_sync_sg_for_cpu(struct device *dev,
}
#endif

+size_t dma_direct_max_mapping_size(struct device *dev);
+
#ifdef CONFIG_HAS_DMA
#include <asm/dma-mapping.h>

@@ -440,6 +443,19 @@ static inline int dma_mapping_error(struct device *dev, dma_addr_t dma_addr)
return 0;
}

+static inline size_t dma_max_mapping_size(struct device *dev)
+{
+ const struct dma_map_ops *ops = get_dma_ops(dev);
+ size_t size = SIZE_MAX;
+
+ if (dma_is_direct(ops))
+ size = dma_direct_max_mapping_size(dev);
+ else if (ops && ops->max_mapping_size)
+ size = ops->max_mapping_size(dev);
+
+ return size;
+}
+
void *dma_alloc_attrs(struct device *dev, size_t size, dma_addr_t *dma_handle,
gfp_t flag, unsigned long attrs);
void dma_free_attrs(struct device *dev, size_t size, void *cpu_addr,
diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 355d16acee6d..84917e1003c4 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -380,3 +380,13 @@ int dma_direct_supported(struct device *dev, u64 mask)
*/
return mask >= __phys_to_dma(dev, min_mask);
}
+
+size_t dma_direct_max_mapping_size(struct device *dev)
+{
+ /*
+ * Return the minimum of the direct DMA limit and the SWIOTLB limit.
+ * Since direct DMA has no limit, it is fine to just return the SWIOTLB
+ * limit.
+ */
+ return swiotlb_max_mapping_size(dev);
+}
--
2.17.1