swiotlb: add common swiotlb_map_ops

Currently all architectures that want to use swiotlb have to implement
their own dma_map_ops instances.  Provide a generic one based on the
x86 implementation which first calls into dma_direct to try a full blown
direct mapping implementation (including e.g. CMA) before falling back
allocating from the swiotlb buffer.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Christian König <christian.koenig@amd.com>

include/linux/swiotlb.h

@@ -66,6 +66,12 @@ extern void swiotlb_tbl_sync_single(struct device *hwdev,
 				    enum dma_sync_target target);
 
 /* Accessory functions. */
+
+void *swiotlb_alloc(struct device *hwdev, size_t size, dma_addr_t *dma_handle,
+		gfp_t flags, unsigned long attrs);
+void swiotlb_free(struct device *dev, size_t size, void *vaddr,
+		dma_addr_t dma_addr, unsigned long attrs);
+
 extern void
 *swiotlb_alloc_coherent(struct device *hwdev, size_t size,
 			dma_addr_t *dma_handle, gfp_t flags);
@@ -126,4 +132,6 @@ extern void swiotlb_print_info(void);
 extern int is_swiotlb_buffer(phys_addr_t paddr);
 extern void swiotlb_set_max_segment(unsigned int);
 
+extern const struct dma_map_ops swiotlb_dma_ops;
+
 #endif /* __LINUX_SWIOTLB_H */

lib/swiotlb.c

@@ -1087,3 +1087,46 @@ swiotlb_dma_supported(struct device *hwdev, u64 mask)
 	return swiotlb_phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
 }
 EXPORT_SYMBOL(swiotlb_dma_supported);
+
+#ifdef CONFIG_DMA_DIRECT_OPS
+void *swiotlb_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle,
+		gfp_t gfp, unsigned long attrs)
+{
+	void *vaddr;
+
+	/*
+	 * Don't print a warning when the first allocation attempt fails.
+	 * swiotlb_alloc_coherent() will print a warning when the DMA memory
+	 * allocation ultimately failed.
+	 */
+	gfp |= __GFP_NOWARN;
+
+	vaddr = dma_direct_alloc(dev, size, dma_handle, gfp, attrs);
+	if (!vaddr)
+		vaddr = swiotlb_alloc_coherent(dev, size, dma_handle, gfp);
+	return vaddr;
+}
+
+void swiotlb_free(struct device *dev, size_t size, void *vaddr,
+		dma_addr_t dma_addr, unsigned long attrs)
+{
+	if (is_swiotlb_buffer(dma_to_phys(dev, dma_addr)))
+		swiotlb_free_coherent(dev, size, vaddr, dma_addr);
+	else
+		dma_direct_free(dev, size, vaddr, dma_addr, attrs);
+}
+
+const struct dma_map_ops swiotlb_dma_ops = {
+	.mapping_error		= swiotlb_dma_mapping_error,
+	.alloc			= swiotlb_alloc,
+	.free			= swiotlb_free,
+	.sync_single_for_cpu	= swiotlb_sync_single_for_cpu,
+	.sync_single_for_device	= swiotlb_sync_single_for_device,
+	.sync_sg_for_cpu	= swiotlb_sync_sg_for_cpu,
+	.sync_sg_for_device	= swiotlb_sync_sg_for_device,
+	.map_sg			= swiotlb_map_sg_attrs,
+	.unmap_sg		= swiotlb_unmap_sg_attrs,
+	.map_page		= swiotlb_map_page,
+	.unmap_page		= swiotlb_unmap_page,
+};
+#endif /* CONFIG_DMA_DIRECT_OPS */