dma-mapping: Add a new dma_need_sync API

Add a new API to check if calls to dma_sync_single_for_{device,cpu} are
required for a given DMA streaming mapping.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200629130359.2690853-2-hch@lst.de

diff --git a/Documentation/core-api/dma-api.rst b/Documentation/core-api/dma-api.rst
index 2d8d2fe..f416204 100644 (file)
--- a/Documentation/core-api/dma-api.rst
+++ b/Documentation/core-api/dma-api.rst
@@ -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.
 
+::
+
+       bool
+       dma_need_sync(struct device *dev, dma_addr_t dma_addr);
+
+Returns %true if dma_sync_single_for_{device,cpu} calls are required to
+transfer memory ownership.  Returns %false if those calls can be skipped.
+
 ::
 
        unsigned long

diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h
index 136f984..8b00673 100644 (file)
--- a/include/linux/dma-direct.h
+++ b/include/linux/dma-direct.h
@@ -87,4 +87,5 @@ int dma_direct_mmap(struct device *dev, struct vm_area_struct *vma,
                void *cpu_addr, dma_addr_t dma_addr, size_t size,
                unsigned long attrs);
 int dma_direct_supported(struct device *dev, u64 mask);
+bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr);
 #endif /* _LINUX_DMA_DIRECT_H */

diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 78f677c..a33ed39 100644 (file)
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -461,6 +461,7 @@ 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);
+bool dma_need_sync(struct device *dev, dma_addr_t dma_addr);
 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,
@@ -571,6 +572,10 @@ static inline size_t dma_max_mapping_size(struct device *dev)
 {
        return 0;
 }
+static inline bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+       return false;
+}
 static inline unsigned long dma_get_merge_boundary(struct device *dev)
 {
        return 0;

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 0a4881e..ecb922a 100644 (file)
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -530,3 +530,9 @@ size_t dma_direct_max_mapping_size(struct device *dev)
                return swiotlb_max_mapping_size(dev);
        return SIZE_MAX;
 }
+
+bool dma_direct_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+       return !dev_is_dma_coherent(dev) ||
+               is_swiotlb_buffer(dma_to_phys(dev, dma_addr));
+}

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 98e3d87..a8c18c9 100644 (file)
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -397,6 +397,16 @@ size_t dma_max_mapping_size(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(dma_max_mapping_size);
 
+bool dma_need_sync(struct device *dev, dma_addr_t dma_addr)
+{
+       const struct dma_map_ops *ops = get_dma_ops(dev);
+
+       if (dma_is_direct(ops))
+               return dma_direct_need_sync(dev, dma_addr);
+       return ops->sync_single_for_cpu || ops->sync_single_for_device;
+}
+EXPORT_SYMBOL_GPL(dma_need_sync);
+
 unsigned long dma_get_merge_boundary(struct device *dev)
 {
        const struct dma_map_ops *ops = get_dma_ops(dev);