From: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
[ 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: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Reviewed-by: Robin Murphy <robin.murphy@xxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Stable-dep-of: d37c120b7312 ("drm/etnaviv: don't truncate physical page address")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
include/linux/dma-mapping.h | 80 +++++++++++++++++++++++++++++++++++++
1 file changed, 80 insertions(+)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index 4d450672b7d66..87cbae4b051f1 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -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)
--
2.39.0
