diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 6d47b4a3ce39..ac0d6376bdad 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -39,6 +39,14 @@
 
 #include "pseries.h"
 
+enum {
+	DDW_QUERY_PE_DMA_WIN  = 0,
+	DDW_CREATE_PE_DMA_WIN = 1,
+	DDW_REMOVE_PE_DMA_WIN = 2,
+
+	DDW_APPLICABLE_SIZE
+};
+
 static struct iommu_table_group *iommu_pseries_alloc_group(int node)
 {
 	struct iommu_table_group *table_group;
@@ -771,12 +779,12 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
 {
 	struct dynamic_dma_window_prop *dwp;
 	struct property *win64;
-	u32 ddw_avail[3];
+	u32 ddw_avail[DDW_APPLICABLE_SIZE];
 	u64 liobn;
 	int ret = 0;
 
 	ret = of_property_read_u32_array(np, "ibm,ddw-applicable",
-					 &ddw_avail[0], 3);
+					 &ddw_avail[0], DDW_APPLICABLE_SIZE);
 
 	win64 = of_find_property(np, DIRECT64_PROPNAME, NULL);
 	if (!win64)
@@ -798,15 +806,15 @@ static void remove_ddw(struct device_node *np, bool remove_prop)
 		pr_debug("%pOF successfully cleared tces in window.\n",
 			 np);
 
-	ret = rtas_call(ddw_avail[2], 1, 1, NULL, liobn);
+	ret = rtas_call(ddw_avail[DDW_REMOVE_PE_DMA_WIN], 1, 1, NULL, liobn);
 	if (ret)
 		pr_warn("%pOF: failed to remove direct window: rtas returned "
 			"%d to ibm,remove-pe-dma-window(%x) %llx\n",
-			np, ret, ddw_avail[2], liobn);
+			np, ret, ddw_avail[DDW_REMOVE_PE_DMA_WIN], liobn);
 	else
 		pr_debug("%pOF: successfully removed direct window: rtas returned "
 			"%d to ibm,remove-pe-dma-window(%x) %llx\n",
-			np, ret, ddw_avail[2], liobn);
+			np, ret, ddw_avail[DDW_REMOVE_PE_DMA_WIN], liobn);
 
 delprop:
 	if (remove_prop)
@@ -889,11 +897,11 @@ static int query_ddw(struct pci_dev *dev, const u32 *ddw_avail,
 	buid = pdn->phb->buid;
 	cfg_addr = ((pdn->busno << 16) | (pdn->devfn << 8));
 
-	ret = rtas_call(ddw_avail[0], 3, 5, (u32 *)query,
-		  cfg_addr, BUID_HI(buid), BUID_LO(buid));
+	ret = rtas_call(ddw_avail[DDW_QUERY_PE_DMA_WIN], 3, 5, (u32 *)query,
+			cfg_addr, BUID_HI(buid), BUID_LO(buid));
 	dev_info(&dev->dev, "ibm,query-pe-dma-windows(%x) %x %x %x"
-		" returned %d\n", ddw_avail[0], cfg_addr, BUID_HI(buid),
-		BUID_LO(buid), ret);
+		" returned %d\n", ddw_avail[DDW_QUERY_PE_DMA_WIN], cfg_addr,
+		 BUID_HI(buid), BUID_LO(buid), ret);
 	return ret;
 }
 
@@ -920,15 +928,16 @@ static int create_ddw(struct pci_dev *dev, const u32 *ddw_avail,
 
 	do {
 		/* extra outputs are LIOBN and dma-addr (hi, lo) */
-		ret = rtas_call(ddw_avail[1], 5, 4, (u32 *)create,
-				cfg_addr, BUID_HI(buid), BUID_LO(buid),
-				page_shift, window_shift);
+		ret = rtas_call(ddw_avail[DDW_CREATE_PE_DMA_WIN], 5, 4,
+				(u32 *)create, cfg_addr, BUID_HI(buid),
+				BUID_LO(buid), page_shift, window_shift);
 	} while (rtas_busy_delay(ret));
 	dev_info(&dev->dev,
 		"ibm,create-pe-dma-window(%x) %x %x %x %x %x returned %d "
-		"(liobn = 0x%x starting addr = %x %x)\n", ddw_avail[1],
-		 cfg_addr, BUID_HI(buid), BUID_LO(buid), page_shift,
-		 window_shift, ret, create->liobn, create->addr_hi, create->addr_lo);
+		"(liobn = 0x%x starting addr = %x %x)\n",
+		 ddw_avail[DDW_CREATE_PE_DMA_WIN], cfg_addr, BUID_HI(buid),
+		 BUID_LO(buid), page_shift, window_shift, ret, create->liobn,
+		 create->addr_hi, create->addr_lo);
 
 	return ret;
 }
@@ -996,7 +1005,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	int page_shift;
 	u64 dma_addr, max_addr;
 	struct device_node *dn;
-	u32 ddw_avail[3];
+	u32 ddw_avail[DDW_APPLICABLE_SIZE];
 	struct direct_window *window;
 	struct property *win64;
 	struct dynamic_dma_window_prop *ddwprop;
@@ -1029,7 +1038,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	 * the property is actually in the parent, not the PE
 	 */
 	ret = of_property_read_u32_array(pdn, "ibm,ddw-applicable",
-					 &ddw_avail[0], 3);
+					 &ddw_avail[0], DDW_APPLICABLE_SIZE);
 	if (ret)
 		goto out_failed;