[PATCH v12 02/10] platform/chrome: cros_ec_typec: Purge blocking switch devlinks

Pin-yen Lin
2023-02-21T09:51:35Z

From: Prashant Malani <pmalani@chromium.org>

When using OF graph, the fw_devlink code will create links between the
individual port driver (cros-ec-typec here) and the parent device for
a Type-C switch (like mode-switch). Since the mode-switch will in turn
have the usb-c-connector (i.e the child of the port driver) as a
supplier, fw_devlink will not be able to resolve the cyclic dependency
correctly.

As a result, the mode-switch driver probe() never runs, so mode-switches
are never registered. Because of that, the port driver probe constantly
fails with -EPROBE_DEFER, because the Type-C connector class requires all
switch devices to be registered prior to port registration.

To break this deadlock and allow the mode-switch registration to occur,
purge all the usb-c-connector nodes' absent suppliers. This eliminates
the connector as a supplier for a switch and allows it to be probed.

Signed-off-by: Prashant Malani <pmalani@chromium.org>
Signed-off-by: Pin-yen Lin <treapking@chromium.org>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-by: Chen-Yu Tsai <wenst@chromium.org>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>

---

(no changes since v11)

Changes in v11:
- Collected Acked-by tag

Changes in v10:
- Collected Reviewed-by and Tested-by tags

Changes in v7:
- Fix the long comment lines

Changes in v6:
- New in v6

drivers/platform/chrome/cros_ec_typec.c | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index 001b0de95a46..bbc95a3ba5a7 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -385,6 +385,16 @@ static int cros_typec_init_ports(struct cros_typec_data *typec)
return -EINVAL;
}

+ /*
+ * OF graph may have set up some device links with switches,
+ * since connectors have their own compatible. Purge these
+ * to avoid a deadlock in switch probe (the switch mistakenly
+ * assumes the connector is a supplier).
+ */
+ if (dev_of_node(dev))
+ device_for_each_child_node(dev, fwnode)
+ fw_devlink_purge_absent_suppliers(fwnode);
+
/* DT uses "reg" to specify port number. */
port_prop = dev->of_node ? "reg" : "port-number";
device_for_each_child_node(dev, fwnode) {
--
2.39.2.637.g21b0678d19-goog