usb: typec: API for controlling USB Type-C Multiplexers

USB Type-C connectors consist of various muxes and switches
that route the pins on the connector to the right locations.
The USB Type-C drivers need to be able to control the muxes,
as they are the ones that know things like the cable plug
orientation, and the current mode that was negotiated with
the partner.

This introduces a small API for registering and controlling
cable plug orientation switches, and separate small API for
registering and controlling pin multiplexer/demultiplexer
switches that are needed with Accessory/Alternate Modes.

Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 191 insertions, 0 deletions

diff --git a/drivers/usb/typec/mux.c b/drivers/usb/typec/mux.c
new file mode 100644
index 000000000000..f89093bd7185
--- /dev/null
+++ b/drivers/usb/typec/mux.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+/**
+ * USB Type-C Multiplexer/DeMultiplexer Switch support
+ *
+ * Copyright (C) 2018 Intel Corporation
+ * Author: Heikki Krogerus <heikki.krogerus@linux.intel.com>
+ *         Hans de Goede <hdegoede@redhat.com>
+ */
+
+#include <linux/device.h>
+#include <linux/list.h>
+#include <linux/mutex.h>
+#include <linux/usb/typec_mux.h>
+
+static DEFINE_MUTEX(switch_lock);
+static DEFINE_MUTEX(mux_lock);
+static LIST_HEAD(switch_list);
+static LIST_HEAD(mux_list);
+
+static void *typec_switch_match(struct device_connection *con, int ep,
+				void *data)
+{
+	struct typec_switch *sw;
+
+	list_for_each_entry(sw, &switch_list, entry)
+		if (!strcmp(con->endpoint[ep], dev_name(sw->dev)))
+			return sw;
+
+	/*
+	 * We only get called if a connection was found, tell the caller to
+	 * wait for the switch to show up.
+	 */
+	return ERR_PTR(-EPROBE_DEFER);
+}
+
+/**
+ * typec_switch_get - Find USB Type-C orientation switch
+ * @dev: The caller device
+ *
+ * Finds a switch linked with @dev. Returns a reference to the switch on
+ * success, NULL if no matching connection was found, or
+ * ERR_PTR(-EPROBE_DEFER) when a connection was found but the switch
+ * has not been enumerated yet.
+ */
+struct typec_switch *typec_switch_get(struct device *dev)
+{
+	struct typec_switch *sw;
+
+	mutex_lock(&switch_lock);
+	sw = device_connection_find_match(dev, "typec-switch", NULL,
+					  typec_switch_match);
+	if (!IS_ERR_OR_NULL(sw))
+		get_device(sw->dev);
+	mutex_unlock(&switch_lock);
+
+	return sw;
+}
+EXPORT_SYMBOL_GPL(typec_switch_get);
+
+/**
+ * typec_put_switch - Release USB Type-C orientation switch
+ * @sw: USB Type-C orientation switch
+ *
+ * Decrement reference count for @sw.
+ */
+void typec_switch_put(struct typec_switch *sw)
+{
+	if (!IS_ERR_OR_NULL(sw))
+		put_device(sw->dev);
+}
+EXPORT_SYMBOL_GPL(typec_switch_put);
+
+/**
+ * typec_switch_register - Register USB Type-C orientation switch
+ * @sw: USB Type-C orientation switch
+ *
+ * This function registers a switch that can be used for routing the correct
+ * data pairs depending on the cable plug orientation from the USB Type-C
+ * connector to the USB controllers. USB Type-C plugs can be inserted
+ * right-side-up or upside-down.
+ */
+int typec_switch_register(struct typec_switch *sw)
+{
+	mutex_lock(&switch_lock);
+	list_add_tail(&sw->entry, &switch_list);
+	mutex_unlock(&switch_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(typec_switch_register);
+
+/**
+ * typec_switch_unregister - Unregister USB Type-C orientation switch
+ * @sw: USB Type-C orientation switch
+ *
+ * Unregister switch that was registered with typec_switch_register().
+ */
+void typec_switch_unregister(struct typec_switch *sw)
+{
+	mutex_lock(&switch_lock);
+	list_del(&sw->entry);
+	mutex_unlock(&switch_lock);
+}
+EXPORT_SYMBOL_GPL(typec_switch_unregister);
+
+/* ------------------------------------------------------------------------- */
+
+static void *typec_mux_match(struct device_connection *con, int ep, void *data)
+{
+	struct typec_mux *mux;
+
+	list_for_each_entry(mux, &mux_list, entry)
+		if (!strcmp(con->endpoint[ep], dev_name(mux->dev)))
+			return mux;
+
+	/*
+	 * We only get called if a connection was found, tell the caller to
+	 * wait for the switch to show up.
+	 */
+	return ERR_PTR(-EPROBE_DEFER);
+}
+
+/**
+ * typec_mux_get - Find USB Type-C Multiplexer
+ * @dev: The caller device
+ *
+ * Finds a mux linked to the caller. This function is primarily meant for the
+ * Type-C drivers. Returns a reference to the mux on success, NULL if no
+ * matching connection was found, or ERR_PTR(-EPROBE_DEFER) when a connection
+ * was found but the mux has not been enumerated yet.
+ */
+struct typec_mux *typec_mux_get(struct device *dev)
+{
+	struct typec_mux *mux;
+
+	mutex_lock(&mux_lock);
+	mux = device_connection_find_match(dev, "typec-mux", NULL,
+					   typec_mux_match);
+	if (!IS_ERR_OR_NULL(mux))
+		get_device(mux->dev);
+	mutex_unlock(&mux_lock);
+
+	return mux;
+}
+EXPORT_SYMBOL_GPL(typec_mux_get);
+
+/**
+ * typec_mux_put - Release handle to a Multiplexer
+ * @mux: USB Type-C Connector Multiplexer/DeMultiplexer
+ *
+ * Decrements reference count for @mux.
+ */
+void typec_mux_put(struct typec_mux *mux)
+{
+	if (!IS_ERR_OR_NULL(mux))
+		put_device(mux->dev);
+}
+EXPORT_SYMBOL_GPL(typec_mux_put);
+
+/**
+ * typec_mux_register - Register Multiplexer routing USB Type-C pins
+ * @mux: USB Type-C Connector Multiplexer/DeMultiplexer
+ *
+ * USB Type-C connectors can be used for alternate modes of operation besides
+ * USB when Accessory/Alternate Modes are supported. With some of those modes,
+ * the pins on the connector need to be reconfigured. This function registers
+ * multiplexer switches routing the pins on the connector.
+ */
+int typec_mux_register(struct typec_mux *mux)
+{
+	mutex_lock(&mux_lock);
+	list_add_tail(&mux->entry, &mux_list);
+	mutex_unlock(&mux_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(typec_mux_register);
+
+/**
+ * typec_mux_unregister - Unregister Multiplexer Switch
+ * @sw: USB Type-C Connector Multiplexer/DeMultiplexer
+ *
+ * Unregister mux that was registered with typec_mux_register().
+ */
+void typec_mux_unregister(struct typec_mux *mux)
+{
+	mutex_lock(&mux_lock);
+	list_del(&mux->entry);
+	mutex_unlock(&mux_lock);
+}
+EXPORT_SYMBOL_GPL(typec_mux_unregister);