Revert "pseries/iommu: Remove DDW on kexec"

After reverting 25ebc45b
("powerpc/pseries/iommu: remove default window before attempting DDW
manipulation"), we no longer remove the base window in enable_ddw.
Therefore, we no longer need to reset the DMA window state in
find_existing_ddw_windows(). We can instead go back to what was done
before, which simply reuses the previous configuration, if any. Further,
this removes the final caller of the reset-pe-dma-windows call, so
remove those functions.

This fixes an EEH on kdump with the ipr driver. The EEH occurs, because
the initcall removes the DDW configuration (64-bit DMA window), but
doesn't ensure the ops are via the IOMMU -- a DMA operation occurs
during probe (still investigating this) and we EEH.

This reverts commit 14b6f00f.
Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/pseries/iommu.c

@@ -787,68 +787,33 @@ static u64 find_existing_ddw(struct device_node *pdn)
 	return dma_addr;
 }
 
-static void __restore_default_window(struct eeh_dev *edev,
-						u32 ddw_restore_token)
-{
-	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
-	 */
-	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));
-	pr_info("ibm,reset-pe-dma-windows(%x) %x %x %x returned %d\n",
-		 ddw_restore_token, cfg_addr, BUID_HI(buid), BUID_LO(buid), ret);
-}
-
 static int find_existing_ddw_windows(void)
 {
+	int len;
 	struct device_node *pdn;
+	struct direct_window *window;
 	const struct dynamic_dma_window_prop *direct64;
-	const u32 *ddw_extensions;
 
 	if (!firmware_has_feature(FW_FEATURE_LPAR))
 		return 0;
 
 	for_each_node_with_property(pdn, DIRECT64_PROPNAME) {
-		direct64 = of_get_property(pdn, DIRECT64_PROPNAME, NULL);
+		direct64 = of_get_property(pdn, DIRECT64_PROPNAME, &len);
 		if (!direct64)
 			continue;
 
-		/*
-		 * We need to ensure the IOMMU table is active when we
-		 * return from the IOMMU setup so that the common code
-		 * can clear the table or find the holes. To that end,
-		 * first, remove any existing DDW configuration.
-		 */
-		remove_ddw(pdn);
+		window = kzalloc(sizeof(*window), GFP_KERNEL);
+		if (!window || len < sizeof(struct dynamic_dma_window_prop)) {
+			kfree(window);
+			remove_ddw(pdn);
+			continue;
+		}
 
-		/*
-		 * Second, if we are running on a new enough level of
-		 * firmware where the restore API is present, use it to
-		 * restore the 32-bit window, which was removed in
-		 * create_ddw.
-		 * If the API is not present, then create_ddw couldn't
-		 * have removed the 32-bit window in the first place, so
-		 * removing the DDW configuration should be sufficient.
-		 */
-		ddw_extensions = of_get_property(pdn, "ibm,ddw-extensions",
-									NULL);
-		if (ddw_extensions && ddw_extensions[0] > 0)
-			__restore_default_window(of_node_to_eeh_dev(pdn),
-							ddw_extensions[1]);
+		window->device = pdn;
+		window->prop = direct64;
+		spin_lock(&direct_window_list_lock);
+		list_add(&window->list, &direct_window_list);
+		spin_unlock(&direct_window_list_lock);
 	}
 
 	return 0;