powerpc/pseries: Device tree should only be updated once after suspend/migrate

The current code makes rtas calls for update-nodes, activate-firmware and then
update-nodes again. The FW provides the same data for both update-nodes calls.
As a result a proc entry exists error is reported for the second update while
adding device nodes.

This patch makes a single rtas call for update-nodes after activating the FW.
It also add rtas_busy delay for the activate-firmware rtas call.
Signed-off-by: Haren Myneni <hbabu@us.ibm.com>
Signed-off-by: Tyrel Datwyler <tyreld@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/mobility.c

@@ -290,13 +290,6 @@ void post_mobility_fixup(void)
 	int rc;
 	int activate_fw_token;
 
-	rc = pseries_devicetree_update(MIGRATION_SCOPE);
-	if (rc) {
-		printk(KERN_ERR "Initial post-mobility device tree update "
-		       "failed: %d\n", rc);
-		return;
-	}
-
 	activate_fw_token = rtas_token("ibm,activate-firmware");
 	if (activate_fw_token == RTAS_UNKNOWN_SERVICE) {
 		printk(KERN_ERR "Could not make post-mobility "
@@ -304,16 +297,17 @@ void post_mobility_fixup(void)
 		return;
 	}
 
-	rc = rtas_call(activate_fw_token, 0, 1, NULL);
-	if (!rc) {
-		rc = pseries_devicetree_update(MIGRATION_SCOPE);
-		if (rc)
-			printk(KERN_ERR "Secondary post-mobility device tree "
-			       "update failed: %d\n", rc);
-	} else {
+	do {
+		rc = rtas_call(activate_fw_token, 0, 1, NULL);
+	} while (rtas_busy_delay(rc));
+
+	if (rc)
 		printk(KERN_ERR "Post-mobility activate-fw failed: %d\n", rc);
-		return;
-	}
+
+	rc = pseries_devicetree_update(MIGRATION_SCOPE);
+	if (rc)
+		printk(KERN_ERR "Post-mobility device tree update "
+			"failed: %d\n", rc);
 
 	return;
 }