linux-kernel - [PATCH v1] usb: typec: tcpm: Don't block probing of consumers of "connector" nodes

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Date:   Wed,  5 May 2021 17:44:22 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Len Brown <lenb@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     John Stultz <john.stultz@...aro.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: [PATCH v1] usb: typec: tcpm: Don't block probing of consumers of
 "connector" nodes

fw_devlink expects DT device nodes with "compatible" property to have
struct devices created for them. Since the connector node might not be
populated as a device, mark it as such so that fw_devlink knows not to
wait on this fwnode being populated as a struct device.

Without this patch, USB functionality can be broken on some boards.

Fixes: f7514a663016 ("of: property: fw_devlink: Add support for remote-endpoint")
Reported-by: John Stultz <john.stultz@...aro.org>
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
Greg,

Probably better to take this in driver-core in case I need more fixes
for fw_devlink on top of this. Those fixes are more likely to land in
driver-core.

Hi John,

Can you please test this and give a Tested-by?

-Saravana

 drivers/base/core.c           | 3 ++-
 drivers/usb/typec/tcpm/tcpm.c | 9 +++++++++
 include/linux/fwnode.h        | 1 +
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 4a8bf8cda52b..628e33939aca 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -150,7 +150,7 @@ void fwnode_links_purge(struct fwnode_handle *fwnode)
 	fwnode_links_purge_consumers(fwnode);
 }
 
-static void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode)
+void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode)
 {
 	struct fwnode_handle *child;
 
@@ -164,6 +164,7 @@ static void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode)
 	fwnode_for_each_available_child_node(fwnode, child)
 		fw_devlink_purge_absent_suppliers(child);
 }
+EXPORT_SYMBOL_GPL(fw_devlink_purge_absent_suppliers);
 
 #ifdef CONFIG_SRCU
 static DEFINE_MUTEX(device_links_lock);
diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index c4fdc00a3bc8..bffa342d4e38 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -5754,6 +5754,15 @@ static int tcpm_fw_get_caps(struct tcpm_port *port,
 	if (!fwnode)
 		return -EINVAL;
 
+	/*
+	 * This fwnode has a "compatible" property, but is never populated as a
+	 * struct device. Instead we simply parse it to read the properties.
+	 * This it breaks fw_devlink=on. To maintain backward compatibility
+	 * with existing DT files, we work around this by deleting any
+	 * fwnode_links to/from this fwnode.
+	 */
+	fw_devlink_purge_absent_suppliers(fwnode);
+
 	/* USB data support is optional */
 	ret = fwnode_property_read_string(fwnode, "data-role", &cap_str);
 	if (ret == 0) {
diff --git a/include/linux/fwnode.h b/include/linux/fwnode.h
index ed4e67a7ff1c..59828516ebaf 100644
--- a/include/linux/fwnode.h
+++ b/include/linux/fwnode.h
@@ -187,5 +187,6 @@ extern u32 fw_devlink_get_flags(void);
 extern bool fw_devlink_is_strict(void);
 int fwnode_link_add(struct fwnode_handle *con, struct fwnode_handle *sup);
 void fwnode_links_purge(struct fwnode_handle *fwnode);
+void fw_devlink_purge_absent_suppliers(struct fwnode_handle *fwnode);
 
 #endif
-- 
2.31.1.527.g47e6f16901-goog