linux-kernel - [PATCH v6 2/7] platform/chrome: cros_ec_typec: Purge blocking switch devlinks

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Date:   Thu, 24 Nov 2022 18:20:51 +0800
From:   Pin-yen Lin <treapking@...omium.org>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Prashant Malani <pmalani@...omium.org>,
        Benson Leung <bleung@...omium.org>,
        Guenter Roeck <groeck@...omium.org>
Cc:     Javier Martinez Canillas <javierm@...hat.com>,
        Stephen Boyd <swboyd@...omium.org>,
        dri-devel@...ts.freedesktop.org,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        devicetree@...r.kernel.org, Pin-yen Lin <treapking@...omium.org>,
        chrome-platform@...ts.linux.dev, linux-acpi@...r.kernel.org,
        Marek Vasut <marex@...x.de>, Xin Ji <xji@...logixsemi.com>,
        Lyude Paul <lyude@...hat.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-kernel@...r.kernel.org, Allen Chen <allen.chen@....com.tw>
Subject: [PATCH v6 2/7] 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>
---

Changes in v6:
- New in v6

 drivers/platform/chrome/cros_ec_typec.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_typec.c b/drivers/platform/chrome/cros_ec_typec.c
index 2a7ff14dc37e..f74e01d18ef3 100644
--- a/drivers/platform/chrome/cros_ec_typec.c
+++ b/drivers/platform/chrome/cros_ec_typec.c
@@ -382,6 +382,15 @@ 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)
+		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) {
-- 
2.38.1.584.g0f3c55d4c2-goog