From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Mon, 20 Jun 2022 20:32:26 +0200
Subject: thunderbolt: ACPI: Replace tb_acpi_find_port() with
 acpi_find_child_by_adr()
Patch-mainline: v6.0-rc1
Git-commit: a73a204b44586c07876f18e329be3fcb713af29b
References: jsc#PED-1408

Use acpi_find_child_by_adr() to find the child matching a given bus
address instead of tb_acpi_find_port() that walks the list of children
of an ACPI device directly for this purpose and drop the latter.

Apart from simplifying the code, this will help to eliminate the
children list head from struct acpi_device as it is redundant and it
is used in questionable ways in some places (in particular, locking is
needed for walking the list pointed to it safely, but it is often
missing).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-by: Lee, Chun-Yi <jlee@suse.com>
---
 drivers/thunderbolt/acpi.c |   29 +++++++----------------------
 1 file changed, 7 insertions(+), 22 deletions(-)

--- a/drivers/thunderbolt/acpi.c
+++ b/drivers/thunderbolt/acpi.c
@@ -301,37 +301,22 @@ static bool tb_acpi_bus_match(struct dev
 	return tb_is_switch(dev) || tb_is_usb4_port_device(dev);
 }
 
-static struct acpi_device *tb_acpi_find_port(struct acpi_device *adev,
-					     const struct tb_port *port)
+static struct acpi_device *tb_acpi_switch_find_companion(struct tb_switch *sw)
 {
-	struct acpi_device *port_adev;
-
-	if (!adev)
-		return NULL;
+	struct acpi_device *adev = NULL;
+	struct tb_switch *parent_sw;
 
 	/*
 	 * Device routers exists under the downstream facing USB4 port
 	 * of the parent router. Their _ADR is always 0.
 	 */
-	list_for_each_entry(port_adev, &adev->children, node) {
-		if (acpi_device_adr(port_adev) == port->port)
-			return port_adev;
-	}
-
-	return NULL;
-}
-
-static struct acpi_device *tb_acpi_switch_find_companion(struct tb_switch *sw)
-{
-	struct acpi_device *adev = NULL;
-	struct tb_switch *parent_sw;
-
 	parent_sw = tb_switch_parent(sw);
 	if (parent_sw) {
 		struct tb_port *port = tb_port_at(tb_route(sw), parent_sw);
 		struct acpi_device *port_adev;
 
-		port_adev = tb_acpi_find_port(ACPI_COMPANION(&parent_sw->dev), port);
+		port_adev = acpi_find_child_by_adr(ACPI_COMPANION(&parent_sw->dev),
+						   port->port);
 		if (port_adev)
 			adev = acpi_find_child_device(port_adev, 0, false);
 	} else {
@@ -364,8 +349,8 @@ static struct acpi_device *tb_acpi_find_
 	if (tb_is_switch(dev))
 		return tb_acpi_switch_find_companion(tb_to_switch(dev));
 	else if (tb_is_usb4_port_device(dev))
-		return tb_acpi_find_port(ACPI_COMPANION(dev->parent),
-					 tb_to_usb4_port_device(dev)->port);
+		return acpi_find_child_by_adr(ACPI_COMPANION(dev->parent),
+					      tb_to_usb4_port_device(dev)->port->port);
 	return NULL;
 }