PCI: Perform reset_resource() and build fail list in sync

Resetting a resource is problematic as it prevents attempting to allocate
the resource later, unless something in between restores the resource.
Similarly, if fail_head does not contain all resources that were reset,
those resources cannot be restored later.

The entire reset/restore cycle adds complexity and leaving resources in the
reset state causes issues to other code such as for checks done in
pci_enable_resources(). Take a small step towards not resetting resources
by delaying reset until the end of resource assignment and build failure
list (fail_head) in sync with the reset to avoid leaving behind resources
that cannot be restored (for the case where the caller provides fail_head
in the first place to allow restore somewhere in the callchain, as is not
all callers pass non-NULL fail_head).

Leave the Expansion ROM check temporarily in place while building the
failure list until an upcoming change that reworks optional resource
handling.

Ideally, whole resource reset could be removed but doing that in one step
would be non-tractable due to complexity of all related code.

Link: https://lore.kernel.org/r/20241216175632.4175-25-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Xiaochun Lee <lixc17@lenovo.com>

drivers/pci/setup-bus.c

@@ -252,9 +252,14 @@ static void reassign_resources_sorted(struct list_head *realloc_head,
 
 		res = add_res->res;
 		dev = add_res->dev;
+		idx = pci_resource_num(dev, res);
 
-		/* Skip resource that has been reset */
-		if (!res->flags)
+		/*
+		 * Skip resource that failed the earlier assignment and is
+		 * not optional as it would just fail again.
+		 */
+		if (!res->parent && resource_size(res) &&
+		    !pci_resource_is_optional(dev, idx))
 			goto out;
 
 		/* Skip this resource if not found in head list */
@@ -267,7 +272,6 @@ static void reassign_resources_sorted(struct list_head *realloc_head,
 		if (!found_match) /* Just skip */
 			continue;
 
-		idx = pci_resource_num(dev, res);
 		res_name = pci_resource_name(dev, idx);
 		add_size = add_res->add_size;
 		align = add_res->min_align;
@@ -277,7 +281,6 @@ static void reassign_resources_sorted(struct list_head *realloc_head,
 				pci_dbg(dev,
 					"%s %pR: ignoring failure in optional allocation\n",
 					res_name, res);
-				reset_resource(res);
 			}
 		} else {
 			res->flags |= add_res->flags &
@@ -332,7 +335,6 @@ static void assign_requested_resources_sorted(struct list_head *head,
 						    0 /* don't care */,
 						    0 /* don't care */);
 			}
-			reset_resource(res);
 		}
 	}
 }
@@ -518,13 +520,34 @@ static void __assign_resources_sorted(struct list_head *head,
 
 requested_and_reassign:
 	/* Satisfy the must-have resource requests */
-	assign_requested_resources_sorted(head, fail_head);
+	assign_requested_resources_sorted(head, NULL);
 
 	/* Try to satisfy any additional optional resource requests */
 	if (!list_empty(realloc_head))
 		reassign_resources_sorted(realloc_head, head);
 
 out:
+	/* Reset any failed resource, cannot use fail_head as it can be NULL. */
+	list_for_each_entry(dev_res, head, list) {
+		res = dev_res->res;
+		dev = dev_res->dev;
+
+		if (res->parent)
+			continue;
+
+		/*
+		 * If the failed resource is a ROM BAR and it will
+		 * be enabled later, don't add it to the list.
+		 */
+		if (fail_head && !pci_resource_is_disabled_rom(res, idx)) {
+			add_to_list(fail_head, dev, res,
+				    0 /* don't care */,
+				    0 /* don't care */);
+		}
+
+		reset_resource(res);
+	}
+
 	free_list(head);
 }