[v14,02/10] platform/chrome: cros_ec_typec: Purge blocking switch devlinks

Commit Message

Pin-yen Lin March 22, 2023, 10:46 a.m. UTC

From: Prashant Malani <[e-mail]>

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 <[e-mail]>
Signed-off-by: Pin-yen Lin <[e-mail]>
Reviewed-by: Chen-Yu Tsai <[e-mail]>
Tested-by: Chen-Yu Tsai <[e-mail]>
Acked-by: Heikki Krogerus <[e-mail]>

---

(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(+)

Comments

AngeloGioacchino Del Regno March 22, 2023, 12:17 p.m. UTC | #1

Il 22/03/23 11:46, Pin-yen Lin ha scritto:
> From: Prashant Malani <[e-mail]>
> 
> 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 <[e-mail]>
> Signed-off-by: Pin-yen Lin <[e-mail]>
> Reviewed-by: Chen-Yu Tsai <[e-mail]>
> Tested-by: Chen-Yu Tsai <[e-mail]>
> Acked-by: Heikki Krogerus <[e-mail]>

Reviewed-by: AngeloGioacchino Del Regno <[e-mail]>

Patch

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index a673c3342470..5911cd9640cb 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -325,6 +325,16 @@  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) {