powerpc: Use the newly added get_required_mask dma_map_ops hook

Now that the generic code has dma_map_ops set, instead of having a
messy ifdef & if block in the base dma_get_required_mask hook push
the computation into the dma ops.

If the ops fails to set the get_required_mask hook default to the
width of dma_addr_t.

This also corrects ibmbus ibmebus_dma_supported to require a 64
bit mask.  I doubt anything is checking or setting the dma mask on
that bus.

Signed-off-by: Milton Miller <miltonm@bga.com>
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-kernel@vger.kernel.org
Cc: benh@kernel.crashing.org
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/dma-swiotlb.c

@@ -24,6 +24,21 @@
 
 unsigned int ppc_swiotlb_enable;
 
+static u64 swiotlb_powerpc_get_required(struct device *dev)
+{
+	u64 end, mask, max_direct_dma_addr = dev->archdata.max_direct_dma_addr;
+
+	end = memblock_end_of_DRAM();
+	if (max_direct_dma_addr && end > max_direct_dma_addr)
+		end = max_direct_dma_addr;
+	end += get_dma_offset(dev);
+
+	mask = 1ULL << (fls64(end) - 1);
+	mask += mask - 1;
+
+	return mask;
+}
+
 /*
  * At the moment, all platforms that use this code only require
  * swiotlb to be used if we're operating on HIGHMEM.  Since
@@ -44,6 +59,7 @@ struct dma_map_ops swiotlb_dma_ops = {
 	.sync_sg_for_cpu = swiotlb_sync_sg_for_cpu,
 	.sync_sg_for_device = swiotlb_sync_sg_for_device,
 	.mapping_error = swiotlb_dma_mapping_error,
+	.get_required_mask = swiotlb_powerpc_get_required,
 };
 
 void pci_dma_dev_setup_swiotlb(struct pci_dev *pdev)