sparc/iommu: create a common helper for map_sg

Share the code for the global and per-page flush map_sg loops using a
simple bool parameter to disable the per-page flush for the former
variant.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/mm/iommu.c

@@ -241,25 +241,9 @@ static dma_addr_t sbus_iommu_map_page_pflush(struct device *dev,
 	return __sbus_iommu_map_page(dev, page, offset, len);
 }
 
-static int sbus_iommu_map_sg_gflush(struct device *dev, struct scatterlist *sgl,
-		int nents, enum dma_data_direction dir, unsigned long attrs)
-{
-	struct scatterlist *sg;
-	int i, n;
-
-	flush_page_for_dma(0);
-
-	for_each_sg(sgl, sg, nents, i) {
-		n = (sg->length + sg->offset + PAGE_SIZE-1) >> PAGE_SHIFT;
-		sg->dma_address = iommu_get_one(dev, sg_page(sg), n) + sg->offset;
-		sg->dma_length = sg->length;
-	}
-
-	return nents;
-}
-
-static int sbus_iommu_map_sg_pflush(struct device *dev, struct scatterlist *sgl,
-		int nents, enum dma_data_direction dir, unsigned long attrs)
+static int __sbus_iommu_map_sg(struct device *dev, struct scatterlist *sgl,
+		int nents, enum dma_data_direction dir, unsigned long attrs,
+		bool per_page_flush)
 {
 	unsigned long page, oldpage = 0;
 	struct scatterlist *sg;
@@ -273,7 +257,7 @@ static int sbus_iommu_map_sg_pflush(struct device *dev, struct scatterlist *sgl,
 		 * XXX Is this a good assumption?
 		 * XXX What if someone else unmaps it here and races us?
 		 */
-		if (!PageHighMem(sg_page(sg))) {
+		if (per_page_flush && !PageHighMem(sg_page(sg))) {
 			page = (unsigned long)page_address(sg_page(sg));
 			for (i = 0; i < n; i++) {
 				if (page != oldpage) {	/* Already flushed? */
@@ -291,6 +275,19 @@ static int sbus_iommu_map_sg_pflush(struct device *dev, struct scatterlist *sgl,
 	return nents;
 }
 
+static int sbus_iommu_map_sg_gflush(struct device *dev, struct scatterlist *sgl,
+		int nents, enum dma_data_direction dir, unsigned long attrs)
+{
+	flush_page_for_dma(0);
+	return __sbus_iommu_map_sg(dev, sgl, nents, dir, attrs, false);
+}
+
+static int sbus_iommu_map_sg_pflush(struct device *dev, struct scatterlist *sgl,
+		int nents, enum dma_data_direction dir, unsigned long attrs)
+{
+	return __sbus_iommu_map_sg(dev, sgl, nents, dir, attrs, true);
+}
+
 static void sbus_iommu_unmap_page(struct device *dev, dma_addr_t dma_addr,
 		size_t len, enum dma_data_direction dir, unsigned long attrs)
 {