powerpc/iommu: Use coherent_dma_mask for alloc_coherent

The IOMMU code has been passing the dma-mask instead of the
coherent_dma_mask to the iommu allocator.  Coherent allocations should
be made using the coherent_dma_mask.

Also update the vio code to ensure the coherent_dma_mask is set. Without
this change drivers, such as ibmvscsi, fail to load with the corrected
dma_iommu_alloc_coherent().
Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/dma-iommu.c

@@ -19,7 +19,7 @@ static void *dma_iommu_alloc_coherent(struct device *dev, size_t size,
 				      dma_addr_t *dma_handle, gfp_t flag)
 {
 	return iommu_alloc_coherent(dev, get_iommu_table_base(dev), size,
-				    dma_handle, device_to_mask(dev), flag,
+				    dma_handle, dev->coherent_dma_mask, flag,
 				    dev_to_node(dev));
 }
 

arch/powerpc/kernel/vio.c

@@ -1257,6 +1257,10 @@ struct vio_dev *vio_register_device_node(struct device_node *of_node)
 	viodev->dev.parent = &vio_bus_device.dev;
 	viodev->dev.bus = &vio_bus_type;
 	viodev->dev.release = vio_dev_release;
+        /* needed to ensure proper operation of coherent allocations
+         * later, in case driver doesn't set it explicitly */
+        dma_set_mask(&viodev->dev, DMA_BIT_MASK(64));
+        dma_set_coherent_mask(&viodev->dev, DMA_BIT_MASK(64));
 
 	/* register with generic device framework */
 	if (device_register(&viodev->dev)) {