[POWERPC] Fix cell IOMMU null pointer explosion on old firmwares

The cell IOMMU fixed mapping support has a null pointer bug if you run
it on older firmwares that don't contain the "dma-ranges" properties.
Fix it and convert to using of_get_next_parent() while we're there.

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

1 files changed, 7 insertions, 8 deletions

diff --git a/arch/powerpc/platforms/cell/iommu.c b/arch/powerpc/platforms/cell/iommu.c
index df330666ccc9..a276064471b3 100644
--- a/arch/powerpc/platforms/cell/iommu.c
+++ b/arch/powerpc/platforms/cell/iommu.c
@@ -26,6 +26,7 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/notifier.h>
+#include <linux/of.h>
 #include <linux/of_platform.h>
 
 #include <asm/prom.h>
@@ -789,18 +790,16 @@ static int __init cell_iommu_init_disabled(void)
 static u64 cell_iommu_get_fixed_address(struct device *dev)
 {
         u64 cpu_addr, size, best_size, pci_addr = OF_BAD_ADDR;
-        struct device_node *tmp, *np;
+        struct device_node *np;
         const u32 *ranges = NULL;
         int i, len, best;
 
-        np = dev->archdata.of_node;
-        of_node_get(np);
-        ranges = of_get_property(np, "dma-ranges", &len);
-        while (!ranges && np) {
-                tmp = of_get_parent(np);
-                of_node_put(np);
-                np = tmp;
+        np = of_node_get(dev->archdata.of_node);
+        while (np) {
                 ranges = of_get_property(np, "dma-ranges", &len);
+                if (ranges)
+                        break;
+                np = of_get_next_parent(np);
         }
 
         if (!ranges) {