powerpc/dma: properly wire up the unmap_page and unmap_sg methods

The unmap methods need to transfer memory ownership back from the
device to the cpu by identical means as dma_sync_*_to_cpu. I'm not
sure powerpc needs to do any work in this transfer direction, but
given that it does invalidate the caches in dma_sync_*_to_cpu already
we should make sure we also do so on unmapping.
Signed-off-by: Christoph Hellwig <hch@lst.de>
[mpe: s/dir/direction in dma_nommu_unmap_page()]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/dma.c

@@ -210,10 +210,15 @@ static int dma_nommu_map_sg(struct device *dev, struct scatterlist *sgl,
 	return nents;
 }
 
-static void dma_nommu_unmap_sg(struct device *dev, struct scatterlist *sg,
+static void dma_nommu_unmap_sg(struct device *dev, struct scatterlist *sgl,
 				int nents, enum dma_data_direction direction,
 				unsigned long attrs)
 {
+	struct scatterlist *sg;
+	int i;
+
+	for_each_sg(sgl, sg, nents, i)
+		__dma_sync_page(sg_page(sg), sg->offset, sg->length, direction);
 }
 
 static u64 dma_nommu_get_required_mask(struct device *dev)
@@ -247,6 +252,8 @@ static inline void dma_nommu_unmap_page(struct device *dev,
 					 enum dma_data_direction direction,
 					 unsigned long attrs)
 {
+	if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+		__dma_sync(bus_to_virt(dma_address), size, direction);
 }
 
 #ifdef CONFIG_NOT_COHERENT_CACHE