From patchwork series 403296

https://patchwork.ozlabs.org//project/linuxppc-dev/list/?series=403296

Author: Fox Snowpatch

arch/powerpc/platforms/pseries/iommu.c

@@ -786,8 +786,16 @@ static void pci_dma_bus_setup_pSeriesLP(struct pci_bus *bus)
 	 * parent bus. During reboot, there will be ibm,dma-window property to
 	 * define DMA window. For kdump, there will at least be default window or DDW
 	 * or both.
+	 * There is an exception to the above. In case the PE goes into frozen
+	 * state, firmware may not provide ibm,dma-window property at the time
+	 * of LPAR reboot.
 	 */
 
+	if (!pdn) {
+		pr_debug("  no ibm,dma-window property !\n");
+		return;
+	}
+
 	ppci = PCI_DN(pdn);
 
 	pr_debug("  parent is %pOF, iommu_table: 0x%p\n",