linux-kernel - [PATCH 08/22] platform/chrome: cros_ec_typec: Purge blocking switch devlinks

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Date: Fri,  9 Feb 2024 23:09:19 -0800
From: Stephen Boyd <swboyd@...omium.org>
To: chrome-platform@...ts.linux.dev
Cc: Prashant Malani <pmalani@...omium.org>,
	linux-kernel@...r.kernel.org,
	patches@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org,
	devicetree@...r.kernel.org,
	linux-arm-msm@...r.kernel.org,
	Douglas Anderson <dianders@...omium.org>,
	Pin-yen Lin <treapking@...omium.org>,
	Chen-Yu Tsai <wenst@...omium.org>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Subject: [PATCH 08/22] platform/chrome: cros_ec_typec: Purge blocking switch devlinks

From: Prashant Malani <pmalani@...omium.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@...omium.org>
Signed-off-by: Pin-yen Lin <treapking@...omium.org>
Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Tested-by: Chen-Yu Tsai <wenst@...omium.org>
Acked-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Link: https://lore.kernel.org/r/20230331091145.737305-3-treapking@chromium.org
Signed-off-by: Stephen Boyd <swboyd@...omium.org>
---
 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 2b2f14a1b711..cc5269a4b2f1 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) {
-- 
https://chromeos.dev