swiotlb: use swiotlb_map_page in swiotlb_map_sg_attrs

No need to duplicate the code - map_sg is equivalent to map_page
for each page in the scatterlist.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

kernel/dma/swiotlb.c

@@ -845,37 +845,27 @@ swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
  * same here.
  */
 int
-swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl, int nelems,
+swiotlb_map_sg_attrs(struct device *dev, struct scatterlist *sgl, int nelems,
 		     enum dma_data_direction dir, unsigned long attrs)
 {
 	struct scatterlist *sg;
 	int i;
 
-	BUG_ON(dir == DMA_NONE);
-
 	for_each_sg(sgl, sg, nelems, i) {
-		phys_addr_t paddr = sg_phys(sg);
-		dma_addr_t dev_addr = phys_to_dma(hwdev, paddr);
-
-		if (swiotlb_force == SWIOTLB_FORCE ||
-		    !dma_capable(hwdev, dev_addr, sg->length)) {
-			phys_addr_t map = map_single(hwdev, sg_phys(sg),
+		sg->dma_address = swiotlb_map_page(dev, sg_page(sg), sg->offset,
 				sg->length, dir, attrs);
-			if (map == SWIOTLB_MAP_ERROR) {
-				/* Don't panic here, we expect map_sg users
-				   to do proper error handling. */
-				attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-				swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
-						       attrs);
-				sg_dma_len(sgl) = 0;
-				return 0;
-			}
-			sg->dma_address = __phys_to_dma(hwdev, map);
-		} else
-			sg->dma_address = dev_addr;
+		if (sg->dma_address == DIRECT_MAPPING_ERROR)
+			goto out_error;
 		sg_dma_len(sg) = sg->length;
 	}
+
 	return nelems;
+
+out_error:
+	swiotlb_unmap_sg_attrs(dev, sgl, i, dir,
+			attrs | DMA_ATTR_SKIP_CPU_SYNC);
+	sg_dma_len(sgl) = 0;
+	return 0;
 }
 
 /*