[POWERPC] Use archdata.dma_data in dma_direct_ops and add the offset

Now that all platforms using dma_direct_offset setup the
archdata.dma_data correctly, we can change the dma_direct_ops to
retrieve the offset from the dma_data, rather than directly from the
global.

While we're here, change the way the offset is used - instead of
or'ing it into the value, add it.  This should have no effect on
current implementations where the offset is far larger than memory,
however in future we may want to use smaller offsets.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/dma_64.c

@@ -117,6 +117,11 @@ EXPORT_SYMBOL(dma_iommu_ops);
  */
 unsigned long dma_direct_offset;
 
+static unsigned long get_dma_direct_offset(struct device *dev)
+{
+	return (unsigned long)dev->archdata.dma_data;
+}
+
 static void *dma_direct_alloc_coherent(struct device *dev, size_t size,
 				       dma_addr_t *dma_handle, gfp_t flag)
 {
@@ -130,7 +135,7 @@ static void *dma_direct_alloc_coherent(struct device *dev, size_t size,
 		return NULL;
 	ret = page_address(page);
 	memset(ret, 0, size);
-	*dma_handle = virt_to_abs(ret) | dma_direct_offset;
+	*dma_handle = virt_to_abs(ret) + get_dma_direct_offset(dev);
 
 	return ret;
 }
@@ -145,7 +150,7 @@ static dma_addr_t dma_direct_map_single(struct device *dev, void *ptr,
 					size_t size,
 					enum dma_data_direction direction)
 {
-	return virt_to_abs(ptr) | dma_direct_offset;
+	return virt_to_abs(ptr) + get_dma_direct_offset(dev);
 }
 
 static void dma_direct_unmap_single(struct device *dev, dma_addr_t dma_addr,
@@ -161,7 +166,7 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl,
 	int i;
 
 	for_each_sg(sgl, sg, nents, i) {
-		sg->dma_address = sg_phys(sg) | dma_direct_offset;
+		sg->dma_address = sg_phys(sg) + get_dma_direct_offset(dev);
 		sg->dma_length = sg->length;
 	}