[PATCH 24/25] PCI: Perform reset_resource() and build fail list in sync

[Ilpo Järvinen]

Resetting resource is problematic as it prevent 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 resource cannot be restored later.

The entire reset/restore cycle adds complexity and leaving resources
into reseted 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).

The Expansion ROM check is temporarily left in place while building the
failure list until the upcoming change which reworks optional resource
handling.

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

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
---
 drivers/pci/setup-bus.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index fec7d68fb971..b61f24a5cfa5 100644
--- a/drivers/pci/setup-bus.c
+++ b/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);
 }
 
-- 
2.39.5