driver core: Add FWLINK_FLAG_IGNORE to completely ignore a fwnode link

A fwnode link between specific supplier-consumer fwnodes can be added
multiple times for multiple reasons. If that dependency doesn't exist,
deleting the fwnode link once doesn't guarantee that it won't get created
again.

So, add FWLINK_FLAG_IGNORE flag to mark a fwnode link as one that needs to
be completely ignored. Since a fwnode link's flags is an OR of all the
flags passed to all the fwnode_link_add() calls to create that specific
fwnode link, the FWLINK_FLAG_IGNORE flag is preserved and can be used to
mark a fwnode link as on that need to be completely ignored until it is
deleted.

Signed-off-by: Saravana Kannan <saravanak@google.com>
Acked-by: "Rafael J. Wysocki" <rafael@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20240305050458.1400667-3-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Saravana Kannan

drivers/base/core.c

@@ -1012,7 +1012,8 @@ static struct fwnode_handle *fwnode_links_check_suppliers(
 		return NULL;
 
 	list_for_each_entry(link, &fwnode->suppliers, c_hook)
-		if (!(link->flags & FWLINK_FLAG_CYCLE))
+		if (!(link->flags &
+		      (FWLINK_FLAG_CYCLE | FWLINK_FLAG_IGNORE)))
 			return link->supplier;
 
 	return NULL;
@@ -2021,6 +2022,9 @@ static bool __fw_devlink_relax_cycles(struct device *con,
 	}
 
 	list_for_each_entry(link, &sup_handle->suppliers, c_hook) {
+		if (link->flags & FWLINK_FLAG_IGNORE)
+			continue;
+
 		if (__fw_devlink_relax_cycles(con, link->supplier)) {
 			__fwnode_link_cycle(link);
 			ret = true;
@@ -2099,6 +2103,9 @@ static int fw_devlink_create_devlink(struct device *con,
 	int ret = 0;
 	u32 flags;
 
+	if (link->flags & FWLINK_FLAG_IGNORE)
+		return 0;
+
 	if (con->fwnode == link->consumer)
 		flags = fw_devlink_get_flags(link->flags);
 	else

include/linux/fwnode.h

@@ -59,8 +59,10 @@ struct fwnode_handle {
  * fwnode link flags
  *
  * CYCLE:	The fwnode link is part of a cycle. Don't defer probe.
+ * IGNORE:	Completely ignore this link, even during cycle detection.
  */
 #define FWLINK_FLAG_CYCLE			BIT(0)
+#define FWLINK_FLAG_IGNORE			BIT(1)
 
 struct fwnode_link {
 	struct fwnode_handle *supplier;