[POWERPC] Fix potential cell IOMMU bug when switching back to default DMA ops

If we get a 64-bit dma mask we switch to the fixed ops and call
cell_dma_dev_setup().  If the driver then switches back to a 32-bit dma
mask for any reason we don't call cell_dma_dev_setup() again, which
has the potential to leave bogus data in dev->archdata.dma_data.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/platforms/cell/iommu.c

@@ -841,19 +841,18 @@ static int dma_set_mask_and_switch(struct device *dev, u64 dma_mask)
 	if (!dev->dma_mask || !dma_supported(dev, dma_mask))
 		return -EIO;
 
-	if (dma_mask == DMA_BIT_MASK(64)) {
-		if (cell_iommu_get_fixed_address(dev) == OF_BAD_ADDR)
-			dev_dbg(dev, "iommu: 64-bit OK, but bad addr\n");
-		else {
-			dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n");
-			set_dma_ops(dev, &dma_iommu_fixed_ops);
-			cell_dma_dev_setup(dev);
-		}
+	if (dma_mask == DMA_BIT_MASK(64) &&
+		cell_iommu_get_fixed_address(dev) != OF_BAD_ADDR)
+	{
+		dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n");
+		set_dma_ops(dev, &dma_iommu_fixed_ops);
 	} else {
 		dev_dbg(dev, "iommu: not 64-bit, using default ops\n");
 		set_dma_ops(dev, get_pci_dma_ops());
 	}
 
+	cell_dma_dev_setup(dev);
+
 	*dev->dma_mask = dma_mask;
 
 	return 0;