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-rw-r--r--include/linux/dma-map-ops.h61
1 files changed, 61 insertions, 0 deletions
diff --git a/include/linux/dma-map-ops.h b/include/linux/dma-map-ops.h
index 31f114f486c4..9bf19b5bf755 100644
--- a/include/linux/dma-map-ops.h
+++ b/include/linux/dma-map-ops.h
@@ -8,6 +8,7 @@
#include <linux/dma-mapping.h>
#include <linux/pgtable.h>
+#include <linux/slab.h>
struct cma;
@@ -277,6 +278,66 @@ static inline bool dev_is_dma_coherent(struct device *dev)
}
#endif /* CONFIG_ARCH_HAS_DMA_COHERENCE_H */
+/*
+ * Check whether potential kmalloc() buffers are safe for non-coherent DMA.
+ */
+static inline bool dma_kmalloc_safe(struct device *dev,
+ enum dma_data_direction dir)
+{
+ /*
+ * If DMA bouncing of kmalloc() buffers is disabled, the kmalloc()
+ * caches have already been aligned to a DMA-safe size.
+ */
+ if (!IS_ENABLED(CONFIG_DMA_BOUNCE_UNALIGNED_KMALLOC))
+ return true;
+
+ /*
+ * kmalloc() buffers are DMA-safe irrespective of size if the device
+ * is coherent or the direction is DMA_TO_DEVICE (non-desctructive
+ * cache maintenance and benign cache line evictions).
+ */
+ if (dev_is_dma_coherent(dev) || dir == DMA_TO_DEVICE)
+ return true;
+
+ return false;
+}
+
+/*
+ * Check whether the given size, assuming it is for a kmalloc()'ed buffer, is
+ * sufficiently aligned for non-coherent DMA.
+ */
+static inline bool dma_kmalloc_size_aligned(size_t size)
+{
+ /*
+ * Larger kmalloc() sizes are guaranteed to be aligned to
+ * ARCH_DMA_MINALIGN.
+ */
+ if (size >= 2 * ARCH_DMA_MINALIGN ||
+ IS_ALIGNED(kmalloc_size_roundup(size), dma_get_cache_alignment()))
+ return true;
+
+ return false;
+}
+
+/*
+ * Check whether the given object size may have originated from a kmalloc()
+ * buffer with a slab alignment below the DMA-safe alignment and needs
+ * bouncing for non-coherent DMA. The pointer alignment is not considered and
+ * in-structure DMA-safe offsets are the responsibility of the caller. Such
+ * code should use the static ARCH_DMA_MINALIGN for compiler annotations.
+ *
+ * The heuristics can have false positives, bouncing unnecessarily, though the
+ * buffers would be small. False negatives are theoretically possible if, for
+ * example, multiple small kmalloc() buffers are coalesced into a larger
+ * buffer that passes the alignment check. There are no such known constructs
+ * in the kernel.
+ */
+static inline bool dma_kmalloc_needs_bounce(struct device *dev, size_t size,
+ enum dma_data_direction dir)
+{
+ return !dma_kmalloc_safe(dev, dir) && !dma_kmalloc_size_aligned(size);
+}
+
void *arch_dma_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
gfp_t gfp, unsigned long attrs);
void arch_dma_free(struct device *dev, size_t size, void *cpu_addr,