pseries/iommu: remove default window before attempting DDW manipulation

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 0915b1a..526076b 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -707,6 +707,21 @@  static int __init disable_ddw_setup(char *str)
 
 early_param("disable_ddw", disable_ddw_setup);
 
+static inline void __remove_ddw(struct device_node *np, const u32 *ddw_avail, u64 liobn)
+{
+	int ret;
+
+	ret = rtas_call(ddw_avail[2], 1, 1, NULL, liobn);
+	if (ret)
+		pr_warning("%s: failed to remove DMA window: rtas returned "
+			"%d to ibm,remove-pe-dma-window(%x) %llx\n",
+			np->full_name, ret, ddw_avail[2], liobn);
+	else
+		pr_debug("%s: successfully removed DMA window: rtas returned "
+			"%d to ibm,remove-pe-dma-window(%x) %llx\n",
+			np->full_name, ret, ddw_avail[2], liobn);
+}
+
 static void remove_ddw(struct device_node *np)
 {
 	struct dynamic_dma_window_prop *dwp;
@@ -736,15 +751,7 @@  static void remove_ddw(struct device_node *np)
 		pr_debug("%s successfully cleared tces in window.\n",
 			 np->full_name);
 
-	ret = rtas_call(ddw_avail[2], 1, 1, NULL, liobn);
-	if (ret)
-		pr_warning("%s: failed to remove direct window: rtas returned "
-			"%d to ibm,remove-pe-dma-window(%x) %llx\n",
-			np->full_name, ret, ddw_avail[2], liobn);
-	else
-		pr_debug("%s: successfully removed direct window: rtas returned "
-			"%d to ibm,remove-pe-dma-window(%x) %llx\n",
-			np->full_name, ret, ddw_avail[2], liobn);
+	__remove_ddw(np, ddw_avail, liobn);
 
 delprop:
 	ret = prom_remove_property(np, win64);
@@ -869,6 +876,35 @@  static int create_ddw(struct pci_dev *dev, const u32 *ddw_avail,
 	return ret;
 }
 
+static void restore_default_window(struct pci_dev *dev,
+				u32 ddw_restore_token, unsigned long liobn)
+{
+	struct eeh_dev *edev;
+	u32 cfg_addr;
+	u64 buid;
+	int ret;
+
+	/*
+	 * Get the config address and phb buid of the PE window.
+	 * Rely on eeh to retrieve this for us.
+	 * Retrieve them from the pci device, not the node with the
+	 * dma-window property
+	 */
+	edev = pci_dev_to_eeh_dev(dev);
+	cfg_addr = edev->config_addr;
+	if (edev->pe_config_addr)
+		cfg_addr = edev->pe_config_addr;
+	buid = edev->phb->buid;
+
+	do {
+		ret = rtas_call(ddw_restore_token, 3, 1, NULL, cfg_addr,
+					BUID_HI(buid), BUID_LO(buid));
+	} while (rtas_busy_delay(ret));
+	dev_info(&dev->dev,
+		"ibm,reset-pe-dma-windows(%x) %x %x %x returned %d\n",
+		 ddw_restore_token, cfg_addr, BUID_HI(buid), BUID_LO(buid), ret);
+}
+
 /*
  * If the PE supports dynamic dma windows, and there is space for a table
  * that can map all pages in a linear offset, then setup such a table,
@@ -889,9 +925,13 @@  static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	u64 dma_addr, max_addr;
 	struct device_node *dn;
 	const u32 *uninitialized_var(ddw_avail);
+	const u32 *uninitialized_var(ddw_extensions);
+	u32 ddw_restore_token = 0;
 	struct direct_window *window;
 	struct property *win64;
 	struct dynamic_dma_window_prop *ddwprop;
+	const void *dma_window = NULL;
+	unsigned long liobn, offset, size;
 
 	mutex_lock(&direct_window_init_mutex);
 
@@ -911,7 +951,40 @@  static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	if (!ddw_avail || len < 3 * sizeof(u32))
 		goto out_unlock;
 
-       /*
+	/*
+	 * the extensions property is only required to exist in certain
+	 * levels of firmware and later
+	 * the ibm,ddw-extensions property is a list with the first
+	 * element containing the number of extensions and each
+	 * subsequent entry is a value corresponding to that extension
+	 */
+	ddw_extensions = of_get_property(pdn, "ibm,ddw-extensions", &len);
+	if (ddw_extensions) {
+		/*
+		 * each new defined extension length should be added to
+		 * the top of the switch so the "earlier" entries also
+		 * get picked up
+		 */
+		switch (ddw_extensions[0]) {
+			/* ibm,reset-pe-dma-windows */
+			case 1:
+				ddw_restore_token = ddw_extensions[1];
+				break;
+		}
+	}
+
+	/*
+	 * Only remove the existing DMA window if we can restore back to
+	 * the default state. Removing the existing window maximizes the
+	 * resources available to firmware for dynamic window creation.
+	 */
+	if (ddw_restore_token) {
+		dma_window = of_get_property(pdn, "ibm,dma-window", NULL);
+		of_parse_dma_window(pdn, dma_window, &liobn, &offset, &size);
+		__remove_ddw(pdn, ddw_avail, liobn);
+	}
+
+	/*
 	 * Query if there is a second window of size to map the
 	 * whole partition.  Query returns number of windows, largest
 	 * block assigned to PE (partition endpoint), and two bitmasks
@@ -920,7 +993,7 @@  static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	dn = pci_device_to_OF_node(dev);
 	ret = query_ddw(dev, ddw_avail, &query);
 	if (ret != 0)
-		goto out_unlock;
+		goto out_restore_window;
 
 	if (query.windows_available == 0) {
 		/*
@@ -929,7 +1002,7 @@  static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 		 * trading in for a larger page size.
 		 */
 		dev_dbg(&dev->dev, "no free dynamic windows");
-		goto out_unlock;
+		goto out_restore_window;
 	}
 	if (query.page_size & 4) {
 		page_shift = 24; /* 16MB */
@@ -940,7 +1013,7 @@  static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	} else {
 		dev_dbg(&dev->dev, "no supported direct page size in mask %x",
 			  query.page_size);
-		goto out_unlock;
+		goto out_restore_window;
 	}
 	/* verify the window * number of ptes will map the partition */
 	/* check largest block * page size > max memory hotplug addr */
@@ -949,14 +1022,14 @@  static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 		dev_dbg(&dev->dev, "can't map partiton max 0x%llx with %u "
 			  "%llu-sized pages\n", max_addr,  query.largest_available_block,
 			  1ULL << page_shift);
-		goto out_unlock;
+		goto out_restore_window;
 	}
 	len = order_base_2(max_addr);
 	win64 = kzalloc(sizeof(struct property), GFP_KERNEL);
 	if (!win64) {
 		dev_info(&dev->dev,
 			"couldn't allocate property for 64bit dma window\n");
-		goto out_unlock;
+		goto out_restore_window;
 	}
 	win64->name = kstrdup(DIRECT64_PROPNAME, GFP_KERNEL);
 	win64->value = ddwprop = kmalloc(sizeof(*ddwprop), GFP_KERNEL);
@@ -1018,6 +1091,10 @@  out_free_prop:
 	kfree(win64->value);
 	kfree(win64);
 
+out_restore_window:
+	if (ddw_restore_token)
+		restore_default_window(dev, ddw_restore_token, liobn);
+
 out_unlock:
 	mutex_unlock(&direct_window_init_mutex);
 	return dma_addr;