[PATCH v7 08/14] usb: otg: add OTG/dual-role core

[Roger Quadros]

It provides APIs for the following tasks

- Registering an OTG/dual-role capable controller
- Registering Host and Gadget controllers to OTG core
- Providing inputs to and kicking the OTG state machine

Provide a dual-role device (DRD) state machine.
DRD mode is a reduced functionality OTG mode. In this mode
we don't support SRP, HNP and dynamic role-swap.

In DRD operation, the controller mode (Host or Peripheral)
is decided based on the ID pin status. Once a cable plug (Type-A
or Type-B) is attached the controller selects the state
and doesn't change till the cable in unplugged and a different
cable type is inserted.

As we don't need most of the complex OTG states and OTG timers
we implement a lean DRD state machine in usb-otg.c.
The DRD state machine is only interested in 2 hardware inputs
'id' and 'b_sess_vld'.

Signed-off-by: Roger Quadros <rogerq@xxxxxx>
---
 drivers/usb/common/Makefile  |    2 +-
 drivers/usb/common/usb-otg.c | 1040 ++++++++++++++++++++++++++++++++++++++++++
 drivers/usb/common/usb-otg.h |   71 +++
 drivers/usb/core/Kconfig     |    2 +-
 include/linux/usb/gadget.h   |    2 +
 include/linux/usb/hcd.h      |    1 +
 include/linux/usb/otg-fsm.h  |    7 +
 include/linux/usb/otg.h      |  154 ++++++-
 8 files changed, 1274 insertions(+), 5 deletions(-)
 create mode 100644 drivers/usb/common/usb-otg.c
 create mode 100644 drivers/usb/common/usb-otg.h

diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
index f8f2c88..730d928 100644
--- a/drivers/usb/common/Makefile
+++ b/drivers/usb/common/Makefile
@@ -7,5 +7,5 @@ usb-common-y			  += common.o
 usb-common-$(CONFIG_USB_LED_TRIG) += led.o
 
 obj-$(CONFIG_USB_ULPI_BUS)	+= ulpi.o
-usbotg-y		:= usb-otg-fsm.o
+usbotg-y		:= usb-otg.o usb-otg-fsm.o
 obj-$(CONFIG_USB_OTG)	+= usbotg.o
diff --git a/drivers/usb/common/usb-otg.c b/drivers/usb/common/usb-otg.c
new file mode 100644
index 0000000..702bca8
--- /dev/null
+++ b/drivers/usb/common/usb-otg.c
@@ -0,0 +1,1040 @@
+/**
+ * drivers/usb/common/usb-otg.c - USB OTG core
+ *
+ * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com
+ * Author: Roger Quadros <rogerq@xxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/ktime.h>
+#include <linux/hrtimer.h>
+#include <linux/list.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/usb/otg.h>
+#include <linux/usb/gadget.h>
+#include <linux/workqueue.h>
+
+#include "usb-otg.h"
+
+struct otg_gcd {
+	struct usb_gadget *gadget;
+	struct otg_gadget_ops *ops;
+};
+
+/* OTG device list */
+LIST_HEAD(otg_list);
+static DEFINE_MUTEX(otg_list_mutex);
+
+/* Hosts and Gadgets waiting for OTG controller */
+struct otg_wait_data {
+	struct device *dev;		/* OTG controller device */
+
+	struct otg_hcd primary_hcd;
+	struct otg_hcd shared_hcd;
+	struct otg_gcd gcd;
+	struct list_head list;
+};
+
+LIST_HEAD(wait_list);
+static DEFINE_MUTEX(wait_list_mutex);
+
+static int usb_otg_hcd_is_primary_hcd(struct usb_hcd *hcd)
+{
+	if (!hcd->primary_hcd)
+		return 1;
+	return hcd == hcd->primary_hcd;
+}
+
+/**
+ * Check if the OTG device is in our wait list and return
+ * otg_wait_data, else NULL.
+ *
+ * wait_list_mutex must be held.
+ */
+static struct otg_wait_data *usb_otg_get_wait(struct device *otg_dev)
+{
+	struct otg_wait_data *wait;
+
+	if (!otg_dev)
+		return NULL;
+
+	/* is there an entry for this otg_dev ?*/
+	list_for_each_entry(wait, &wait_list, list) {
+		if (wait->dev == otg_dev)
+			return wait;
+	}
+
+	return NULL;
+}
+
+/**
+ * Add the hcd to our wait list
+ */
+static int usb_otg_hcd_wait_add(struct device *otg_dev, struct usb_hcd *hcd,
+				unsigned int irqnum, unsigned long irqflags,
+				struct otg_hcd_ops *ops)
+{
+	struct otg_wait_data *wait;
+	int ret = -EINVAL;
+
+	mutex_lock(&wait_list_mutex);
+
+	wait = usb_otg_get_wait(otg_dev);
+	if (!wait) {
+		/* Not yet in wait list? allocate and add */
+		wait = kzalloc(sizeof(*wait), GFP_KERNEL);
+		if (!wait) {
+			ret = -ENOMEM;
+			goto fail;
+		}
+
+		wait->dev = otg_dev;
+		list_add_tail(&wait->list, &wait_list);
+	}
+
+	if (usb_otg_hcd_is_primary_hcd(hcd)) {
+		if (wait->primary_hcd.hcd)	/* already assigned? */
+			goto fail;
+
+		wait->primary_hcd.hcd = hcd;
+		wait->primary_hcd.irqnum = irqnum;
+		wait->primary_hcd.irqflags = irqflags;
+		wait->primary_hcd.ops = ops;
+		wait->primary_hcd.otg_dev = otg_dev;
+	} else {
+		if (wait->shared_hcd.hcd)	/* already assigned? */
+			goto fail;
+
+		wait->shared_hcd.hcd = hcd;
+		wait->shared_hcd.irqnum = irqnum;
+		wait->shared_hcd.irqflags = irqflags;
+		wait->shared_hcd.ops = ops;
+		wait->shared_hcd.otg_dev = otg_dev;
+	}
+
+	mutex_unlock(&wait_list_mutex);
+	return 0;
+
+fail:
+	mutex_unlock(&wait_list_mutex);
+	return ret;
+}
+
+/**
+ * Check and free wait list entry if empty
+ *
+ * wait_list_mutex must be held
+ */
+static void usb_otg_check_free_wait(struct otg_wait_data *wait)
+{
+	if (wait->primary_hcd.hcd || wait->shared_hcd.hcd || wait->gcd.gadget)
+		return;
+
+	list_del(&wait->list);
+	kfree(wait);
+}
+
+/**
+ * Remove the hcd from our wait list
+ */
+static int usb_otg_hcd_wait_remove(struct usb_hcd *hcd)
+{
+	struct otg_wait_data *wait;
+
+	mutex_lock(&wait_list_mutex);
+
+	/* is there an entry for this hcd ?*/
+	list_for_each_entry(wait, &wait_list, list) {
+		if (wait->primary_hcd.hcd == hcd) {
+			wait->primary_hcd.hcd = 0;
+			goto found;
+		} else if (wait->shared_hcd.hcd == hcd) {
+			wait->shared_hcd.hcd = 0;
+			goto found;
+		}
+	}
+
+	mutex_unlock(&wait_list_mutex);
+	return -EINVAL;
+
+found:
+	usb_otg_check_free_wait(wait);
+	mutex_unlock(&wait_list_mutex);
+
+	return 0;
+}
+
+/**
+ * Add the gadget to our wait list
+ */
+static int usb_otg_gadget_wait_add(struct device *otg_dev,
+				   struct usb_gadget *gadget,
+				   struct otg_gadget_ops *ops)
+{
+	struct otg_wait_data *wait;
+	int ret = -EINVAL;
+
+	mutex_lock(&wait_list_mutex);
+
+	wait = usb_otg_get_wait(otg_dev);
+	if (!wait) {
+		/* Not yet in wait list? allocate and add */
+		wait = kzalloc(sizeof(*wait), GFP_KERNEL);
+		if (!wait) {
+			ret = -ENOMEM;
+			goto fail;
+		}
+
+		wait->dev = otg_dev;
+		list_add_tail(&wait->list, &wait_list);
+	}
+
+	if (wait->gcd.gadget) /* already assigned? */
+		goto fail;
+
+	wait->gcd.gadget = gadget;
+	wait->gcd.ops = ops;
+	mutex_unlock(&wait_list_mutex);
+
+	return 0;
+
+fail:
+	mutex_unlock(&wait_list_mutex);
+	return ret;
+}
+
+/**
+ * Remove the gadget from our wait list
+ */
+static int usb_otg_gadget_wait_remove(struct usb_gadget *gadget)
+{
+	struct otg_wait_data *wait;
+
+	mutex_lock(&wait_list_mutex);
+
+	/* is there an entry for this gadget ?*/
+	list_for_each_entry(wait, &wait_list, list) {
+		if (wait->gcd.gadget == gadget) {
+			wait->gcd.gadget = 0;
+			goto found;
+		}
+	}
+
+	mutex_unlock(&wait_list_mutex);
+
+	return -EINVAL;
+
+found:
+	usb_otg_check_free_wait(wait);
+	mutex_unlock(&wait_list_mutex);
+
+	return 0;
+}
+
+/**
+ * Register pending host/gadget and remove entry from wait list
+ */
+static void usb_otg_flush_wait(struct device *otg_dev)
+{
+	struct otg_wait_data *wait;
+	struct otg_hcd *whcd;
+	struct otg_gcd *wgcd;
+
+	mutex_lock(&wait_list_mutex);
+
+	wait = usb_otg_get_wait(otg_dev);
+	if (!wait)
+		goto done;
+
+	dev_dbg(otg_dev, "otg: registering pending host/gadget\n");
+	wgcd = &wait->gcd;
+	if (wgcd->gadget)
+		usb_otg_register_gadget(wgcd->gadget, wgcd->ops);
+
+	whcd = &wait->primary_hcd;
+	if (whcd->hcd)
+		usb_otg_register_hcd(whcd->hcd, whcd->irqnum, whcd->irqflags,
+				     whcd->ops);
+
+	whcd = &wait->shared_hcd;
+	if (whcd->hcd)
+		usb_otg_register_hcd(whcd->hcd, whcd->irqnum, whcd->irqflags,
+				     whcd->ops);
+
+	list_del(&wait->list);
+	kfree(wait);
+
+done:
+	mutex_unlock(&wait_list_mutex);
+}
+
+/**
+ * Check if the OTG device is in our OTG list and return
+ * usb_otg data, else NULL.
+ *
+ * otg_list_mutex must be held.
+ */
+static struct usb_otg *usb_otg_get_data(struct device *otg_dev)
+{
+	struct usb_otg *otg;
+
+	if (!otg_dev)
+		return NULL;
+
+	list_for_each_entry(otg, &otg_list, list) {
+		if (otg->dev == otg_dev)
+			return otg;
+	}
+
+	return NULL;
+}
+
+/**
+ * usb_otg_start_host - start/stop the host controller
+ * @otg:	usb_otg instance
+ * @on:		true to start, false to stop
+ *
+ * Start/stop the USB host controller. This function is meant
+ * for use by the OTG controller driver.
+ */
+int usb_otg_start_host(struct usb_otg *otg, int on)
+{
+	struct otg_hcd_ops *hcd_ops = otg->hcd_ops;
+
+	dev_dbg(otg->dev, "otg: %s %d\n", __func__, on);
+	if (!otg->host) {
+		WARN_ONCE(1, "otg: fsm running without host\n");
+		return 0;
+	}
+
+	if (on) {
+		if (otg->flags & OTG_FLAG_HOST_RUNNING)
+			return 0;
+
+		otg->flags |= OTG_FLAG_HOST_RUNNING;
+
+		/* start host */
+		hcd_ops->add(otg->primary_hcd.hcd, otg->primary_hcd.irqnum,
+			     otg->primary_hcd.irqflags);
+		if (otg->shared_hcd.hcd) {
+			hcd_ops->add(otg->shared_hcd.hcd,
+				     otg->shared_hcd.irqnum,
+				     otg->shared_hcd.irqflags);
+		}
+	} else {
+		if (!(otg->flags & OTG_FLAG_HOST_RUNNING))
+			return 0;
+
+		otg->flags &= ~OTG_FLAG_HOST_RUNNING;
+
+		/* stop host */
+		if (otg->shared_hcd.hcd)
+			hcd_ops->remove(otg->shared_hcd.hcd);
+
+		hcd_ops->remove(otg->primary_hcd.hcd);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_start_host);
+
+/**
+ * usb_otg_start_gadget - start/stop the gadget controller
+ * @otg:	usb_otg instance
+ * @on:		true to start, false to stop
+ *
+ * Start/stop the USB gadget controller. This function is meant
+ * for use by the OTG controller driver.
+ */
+int usb_otg_start_gadget(struct usb_otg *otg, int on)
+{
+	struct usb_gadget *gadget = otg->gadget;
+
+	dev_dbg(otg->dev, "otg: %s %d\n", __func__, on);
+	if (!gadget) {
+		WARN_ONCE(1, "otg: fsm running without gadget\n");
+		return 0;
+	}
+
+	if (on) {
+		if (otg->flags & OTG_FLAG_GADGET_RUNNING)
+			return 0;
+
+		otg->flags |= OTG_FLAG_GADGET_RUNNING;
+		otg->gadget_ops->start(otg->gadget);
+	} else {
+		if (!(otg->flags & OTG_FLAG_GADGET_RUNNING))
+			return 0;
+
+		otg->flags &= ~OTG_FLAG_GADGET_RUNNING;
+		otg->gadget_ops->stop(otg->gadget);
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_start_gadget);
+
+/**
+ * Change USB protocol when there is a protocol change.
+ * fsm->lock must be held.
+ */
+static int drd_set_protocol(struct otg_fsm *fsm, int protocol)
+{
+	struct usb_otg *otg = container_of(fsm, struct usb_otg, fsm);
+	int ret = 0;
+
+	if (fsm->protocol != protocol) {
+		dev_dbg(otg->dev, "otg: changing role fsm->protocol= %d; new protocol= %d\n",
+			fsm->protocol, protocol);
+		/* stop old protocol */
+		if (fsm->protocol == PROTO_HOST)
+			ret = otg_start_host(otg, 0);
+		else if (fsm->protocol == PROTO_GADGET)
+			ret = otg_start_gadget(otg, 0);
+		if (ret)
+			return ret;
+
+		/* start new protocol */
+		if (protocol == PROTO_HOST)
+			ret = otg_start_host(otg, 1);
+		else if (protocol == PROTO_GADGET)
+			ret = otg_start_gadget(otg, 1);
+		if (ret)
+			return ret;
+
+		fsm->protocol = protocol;
+		return 0;
+	}
+
+	return 0;
+}
+
+/**
+ * Called when entering a DRD state.
+ * fsm->lock must be held.
+ */
+static void drd_set_state(struct otg_fsm *fsm, enum usb_otg_state new_state)
+{
+	struct usb_otg *otg = container_of(fsm, struct usb_otg, fsm);
+
+	if (otg->state == new_state)
+		return;
+
+	fsm->state_changed = 1;
+	dev_dbg(otg->dev, "otg: set state: %s\n",
+		usb_otg_state_string(new_state));
+	switch (new_state) {
+	case OTG_STATE_B_IDLE:
+		drd_set_protocol(fsm, PROTO_UNDEF);
+		otg_drv_vbus(otg, 0);
+		break;
+	case OTG_STATE_B_PERIPHERAL:
+		drd_set_protocol(fsm, PROTO_GADGET);
+		otg_drv_vbus(otg, 0);
+		break;
+	case OTG_STATE_A_HOST:
+		drd_set_protocol(fsm, PROTO_HOST);
+		otg_drv_vbus(otg, 1);
+		break;
+	default:
+		dev_warn(otg->dev, "%s: otg: invalid state: %s\n",
+			 __func__, usb_otg_state_string(new_state));
+		break;
+	}
+
+	otg->state = new_state;
+}
+
+/**
+ * DRD state change judgement
+ *
+ * For DRD we're only interested in some of the OTG states
+ * i.e. OTG_STATE_B_IDLE: both peripheral and host are stopped
+ *	OTG_STATE_B_PERIPHERAL: peripheral active
+ *	OTG_STATE_A_HOST: host active
+ * we're only interested in the following inputs
+ *	fsm->id, fsm->b_sess_vld
+ */
+int drd_statemachine(struct usb_otg *otg)
+{
+	struct otg_fsm *fsm = &otg->fsm;
+	enum usb_otg_state state;
+	int ret;
+
+	mutex_lock(&fsm->lock);
+
+	fsm->state_changed = 0;
+	state = otg->state;
+
+	switch (state) {
+	case OTG_STATE_UNDEFINED:
+		if (!fsm->id)
+			drd_set_state(fsm, OTG_STATE_A_HOST);
+		else if (fsm->id && fsm->b_sess_vld)
+			drd_set_state(fsm, OTG_STATE_B_PERIPHERAL);
+		else
+			drd_set_state(fsm, OTG_STATE_B_IDLE);
+		break;
+	case OTG_STATE_B_IDLE:
+		if (!fsm->id)
+			drd_set_state(fsm, OTG_STATE_A_HOST);
+		else if (fsm->b_sess_vld)
+			drd_set_state(fsm, OTG_STATE_B_PERIPHERAL);
+		break;
+	case OTG_STATE_B_PERIPHERAL:
+		if (!fsm->id)
+			drd_set_state(fsm, OTG_STATE_A_HOST);
+		else if (!fsm->b_sess_vld)
+			drd_set_state(fsm, OTG_STATE_B_IDLE);
+		break;
+	case OTG_STATE_A_HOST:
+		if (fsm->id && fsm->b_sess_vld)
+			drd_set_state(fsm, OTG_STATE_B_PERIPHERAL);
+		else if (fsm->id && !fsm->b_sess_vld)
+			drd_set_state(fsm, OTG_STATE_B_IDLE);
+		break;
+
+	default:
+		dev_err(otg->dev, "%s: otg: invalid usb-drd state: %s\n",
+			__func__, usb_otg_state_string(state));
+		break;
+	}
+
+	ret = fsm->state_changed;
+	mutex_unlock(&fsm->lock);
+	dev_dbg(otg->dev, "otg: quit statemachine, changed %d\n",
+		fsm->state_changed);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(drd_statemachine);
+
+/**
+ * Dual-role device (DRD) work function
+ */
+static void usb_drd_work(struct work_struct *work)
+{
+	struct usb_otg *otg = container_of(work, struct usb_otg, work);
+
+	pm_runtime_get_sync(otg->dev);
+	drd_statemachine(otg);
+	pm_runtime_put_sync(otg->dev);
+}
+
+/**
+ * usb_otg_register() - Register the OTG/dual-role device to OTG core
+ * @dev: OTG/dual-role controller device.
+ * @config: OTG configuration.
+ *
+ * Registers the OTG/dual-role controller device with the USB OTG core.
+ *
+ * Return: struct usb_otg * if success, ERR_PTR() if error.
+ */
+struct usb_otg *usb_otg_register(struct device *dev,
+				 struct usb_otg_config *config)
+{
+	struct usb_otg *otg;
+	struct otg_wait_data *wait;
+	int ret = 0;
+
+	if (!dev || !config || !config->fsm_ops)
+		return ERR_PTR(-EINVAL);
+
+	/* already in list? */
+	mutex_lock(&otg_list_mutex);
+	if (usb_otg_get_data(dev)) {
+		dev_err(dev, "otg: %s: device already in otg list\n",
+			__func__);
+		ret = -EINVAL;
+		goto unlock;
+	}
+
+	/* allocate and add to list */
+	otg = kzalloc(sizeof(*otg), GFP_KERNEL);
+	if (!otg) {
+		ret = -ENOMEM;
+		goto unlock;
+	}
+
+	otg->dev = dev;
+	otg->caps = config->otg_caps;
+
+	if ((otg->caps->hnp_support || otg->caps->srp_support ||
+	     otg->caps->adp_support) && !config->otg_work) {
+		dev_err(dev,
+			"otg: otg_work must be provided for OTG support\n");
+		ret = -EINVAL;
+		goto err_wq;
+	}
+
+	if (config->otg_work)	/* custom otg_work ? */
+		INIT_WORK(&otg->work, config->otg_work);
+	else
+		INIT_WORK(&otg->work, usb_drd_work);
+
+	otg->wq = create_singlethread_workqueue("usb_otg");
+	if (!otg->wq) {
+		dev_err(dev, "otg: %s: can't create workqueue\n",
+			__func__);
+		ret = -ENOMEM;
+		goto err_wq;
+	}
+
+	/* set otg ops */
+	otg->fsm.ops = config->fsm_ops;
+
+	mutex_init(&otg->fsm.lock);
+
+	list_add_tail(&otg->list, &otg_list);
+	mutex_unlock(&otg_list_mutex);
+
+	/* were we in wait list? */
+	mutex_lock(&wait_list_mutex);
+	wait = usb_otg_get_wait(dev);
+	mutex_unlock(&wait_list_mutex);
+	if (wait) {
+		/* register pending host/gadget and flush from list */
+		usb_otg_flush_wait(dev);
+	}
+
+	return otg;
+
+err_wq:
+	kfree(otg);
+unlock:
+	mutex_unlock(&otg_list_mutex);
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(usb_otg_register);
+
+/**
+ * usb_otg_unregister() - Unregister the OTG/dual-role device from USB OTG core
+ * @dev: OTG controller device.
+ *
+ * Unregisters the OTG/dual-role controller device from USB OTG core.
+ * Prevents unregistering till both the associated Host and Gadget controllers
+ * have unregistered from the OTG core.
+ *
+ * Return: 0 on success, error value otherwise.
+ */
+int usb_otg_unregister(struct device *dev)
+{
+	struct usb_otg *otg;
+
+	mutex_lock(&otg_list_mutex);
+	otg = usb_otg_get_data(dev);
+	if (!otg) {
+		dev_err(dev, "otg: %s: device not in otg list\n",
+			__func__);
+		mutex_unlock(&otg_list_mutex);
+		return -EINVAL;
+	}
+
+	/* prevent unregister till both host & gadget have unregistered */
+	if (otg->host || otg->gadget) {
+		dev_err(dev, "otg: %s: host/gadget still registered\n",
+			__func__);
+		return -EBUSY;
+	}
+
+	/* OTG FSM is halted when host/gadget unregistered */
+	destroy_workqueue(otg->wq);
+
+	/* remove from otg list */
+	list_del(&otg->list);
+	kfree(otg);
+	mutex_unlock(&otg_list_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_unregister);
+
+/**
+ * start/kick the OTG FSM if we can
+ * fsm->lock must be held
+ */
+static void usb_otg_start_fsm(struct usb_otg *otg)
+{
+	struct otg_fsm *fsm = &otg->fsm;
+
+	if (fsm->running)
+		goto kick_fsm;
+
+	if (!otg->host) {
+		dev_info(otg->dev, "otg: can't start till host registers\n");
+		return;
+	}
+
+	if (!otg->gadget) {
+		dev_info(otg->dev, "otg: can't start till gadget registers\n");
+		return;
+	}
+
+	fsm->running = true;
+kick_fsm:
+	queue_work(otg->wq, &otg->work);
+}
+
+/**
+ * stop the OTG FSM. Stops Host & Gadget controllers as well.
+ * fsm->lock must be held
+ */
+static void usb_otg_stop_fsm(struct usb_otg *otg)
+{
+	struct otg_fsm *fsm = &otg->fsm;
+
+	if (!fsm->running)
+		return;
+
+	/* no more new events queued */
+	fsm->running = false;
+
+	flush_workqueue(otg->wq);
+	otg->state = OTG_STATE_UNDEFINED;
+
+	/* stop host/gadget immediately */
+	if (fsm->protocol == PROTO_HOST)
+		otg_start_host(otg, 0);
+	else if (fsm->protocol == PROTO_GADGET)
+		otg_start_gadget(otg, 0);
+	fsm->protocol = PROTO_UNDEF;
+}
+
+/**
+ * usb_otg_sync_inputs - Sync OTG inputs with the OTG state machine
+ * @fsm:	OTG FSM instance
+ *
+ * Used by the OTG driver to update the inputs to the OTG
+ * state machine.
+ *
+ * Can be called in IRQ context.
+ */
+void usb_otg_sync_inputs(struct usb_otg *otg)
+{
+	/* Don't kick FSM till it has started */
+	if (!otg->fsm.running)
+		return;
+
+	/* Kick FSM */
+	queue_work(otg->wq, &otg->work);
+}
+EXPORT_SYMBOL_GPL(usb_otg_sync_inputs);
+
+/**
+ * usb_otg_kick_fsm - Kick the OTG state machine
+ * @otg_dev:	OTG controller device
+ *
+ * Used by USB host/device stack to sync OTG related
+ * events to the OTG state machine.
+ * e.g. change in host_bus->b_hnp_enable, gadget->b_hnp_enable
+ *
+ * Returns: 0 on success, error value otherwise.
+ */
+int usb_otg_kick_fsm(struct device *otg_dev)
+{
+	struct usb_otg *otg;
+
+	mutex_lock(&otg_list_mutex);
+	otg = usb_otg_get_data(otg_dev);
+	mutex_unlock(&otg_list_mutex);
+	if (!otg) {
+		dev_dbg(otg_dev, "otg: %s: invalid otg device\n",
+			__func__);
+		return -ENODEV;
+	}
+
+	usb_otg_sync_inputs(otg);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_kick_fsm);
+
+/**
+ * usb_otg_register_hcd - Register the host controller to OTG core
+ * @hcd:	host controller device
+ * @irqnum:	interrupt number
+ * @irqflags:	interrupt flags
+ * @ops:	HCD ops to interface with the HCD
+ *
+ * This is used by the USB Host stack to register the host controller
+ * to the OTG core. Host controller must not be started by the
+ * caller as it is left upto the OTG state machine to do so.
+ * hcd->otg_dev must contain the related otg controller device.
+ *
+ * Returns: 0 on success, error value otherwise.
+ */
+int usb_otg_register_hcd(struct usb_hcd *hcd, unsigned int irqnum,
+			 unsigned long irqflags, struct otg_hcd_ops *ops)
+{
+	struct usb_otg *otg;
+	struct device *hcd_dev = hcd->self.controller;
+	struct device *otg_dev = hcd->otg_dev;
+
+	if (!otg_dev)
+		return -EINVAL;
+
+	/* we're otg but otg controller might not yet be registered */
+	mutex_lock(&otg_list_mutex);
+	otg = usb_otg_get_data(otg_dev);
+	mutex_unlock(&otg_list_mutex);
+	if (!otg) {
+		dev_dbg(hcd_dev,
+			"otg: controller not yet registered. waiting..\n");
+		/*
+		 * otg controller might register later. Put the hcd in
+		 * wait list and call us back when ready
+		 */
+		if (usb_otg_hcd_wait_add(otg_dev, hcd, irqnum, irqflags, ops)) {
+			dev_err(hcd_dev, "otg: failed to add hcd to wait list\n");
+			return -EINVAL;
+		}
+
+		return 0;
+	}
+
+	/* HCD will be started by OTG fsm when needed */
+	mutex_lock(&otg->fsm.lock);
+	if (otg->primary_hcd.hcd) {
+		/* probably a shared HCD ? */
+		if (usb_otg_hcd_is_primary_hcd(hcd)) {
+			dev_err(otg_dev, "otg: primary host already registered\n");
+			goto err;
+		}
+
+		if (hcd->shared_hcd == otg->primary_hcd.hcd) {
+			if (otg->shared_hcd.hcd) {
+				dev_err(otg_dev, "otg: shared host already registered\n");
+				goto err;
+			}
+
+			otg->shared_hcd.hcd = hcd;
+			otg->shared_hcd.irqnum = irqnum;
+			otg->shared_hcd.irqflags = irqflags;
+			otg->shared_hcd.ops = ops;
+			dev_info(otg_dev, "otg: shared host %s registered\n",
+				 dev_name(hcd->self.controller));
+		} else {
+			dev_err(otg_dev, "otg: invalid shared host %s\n",
+				dev_name(hcd->self.controller));
+			goto err;
+		}
+	} else {
+		if (!usb_otg_hcd_is_primary_hcd(hcd)) {
+			dev_err(otg_dev, "otg: primary host must be registered first\n");
+			goto err;
+		}
+
+		otg->primary_hcd.hcd = hcd;
+		otg->primary_hcd.irqnum = irqnum;
+		otg->primary_hcd.irqflags = irqflags;
+		otg->primary_hcd.ops = ops;
+		otg->hcd_ops = ops;
+		dev_info(otg_dev, "otg: primary host %s registered\n",
+			 dev_name(hcd->self.controller));
+	}
+
+	/*
+	 * we're ready only if we have shared HCD
+	 * or we don't need shared HCD.
+	 */
+	if (otg->shared_hcd.hcd || !otg->primary_hcd.hcd->shared_hcd) {
+		otg->host = hcd_to_bus(hcd);
+		/* FIXME: set bus->otg_port if this is true OTG port with HNP */
+
+		/* start FSM */
+		usb_otg_start_fsm(otg);
+	} else {
+		dev_dbg(otg_dev, "otg: can't start till shared host registers\n");
+	}
+
+	mutex_unlock(&otg->fsm.lock);
+
+	return 0;
+
+err:
+	mutex_unlock(&otg->fsm.lock);
+	return -EINVAL;
+}
+EXPORT_SYMBOL_GPL(usb_otg_register_hcd);
+
+/**
+ * usb_otg_unregister_hcd - Unregister the host controller from OTG core
+ * @hcd:	host controller device
+ *
+ * This is used by the USB Host stack to unregister the host controller
+ * from the OTG core. Ensures that host controller is not running
+ * on successful return.
+ *
+ * Returns: 0 on success, error value otherwise.
+ */
+int usb_otg_unregister_hcd(struct usb_hcd *hcd)
+{
+	struct usb_otg *otg;
+	struct device *hcd_dev = hcd_to_bus(hcd)->controller;
+	struct device *otg_dev = hcd->otg_dev;
+
+	if (!otg_dev)
+		return -EINVAL;	/* we're definitely not OTG */
+
+	mutex_lock(&otg_list_mutex);
+	otg = usb_otg_get_data(otg_dev);
+	mutex_unlock(&otg_list_mutex);
+	if (!otg) {
+		/* are we in wait list? */
+		if (!usb_otg_hcd_wait_remove(hcd))
+			return 0;
+
+		dev_dbg(hcd_dev, "otg: host wasn't registered with otg\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&otg->fsm.lock);
+	if (hcd == otg->primary_hcd.hcd) {
+		otg->primary_hcd.hcd = NULL;
+		dev_info(otg_dev, "otg: primary host %s unregistered\n",
+			 dev_name(hcd_dev));
+	} else if (hcd == otg->shared_hcd.hcd) {
+		otg->shared_hcd.hcd = NULL;
+		dev_info(otg_dev, "otg: shared host %s unregistered\n",
+			 dev_name(hcd_dev));
+	} else {
+		dev_err(otg_dev, "otg: host %s wasn't registered with otg\n",
+			dev_name(hcd_dev));
+		mutex_unlock(&otg->fsm.lock);
+		return -EINVAL;
+	}
+
+	/* stop FSM & Host */
+	usb_otg_stop_fsm(otg);
+	otg->host = NULL;
+
+	mutex_unlock(&otg->fsm.lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_unregister_hcd);
+
+/**
+ * usb_otg_register_gadget - Register the gadget controller to OTG core
+ * @gadget:	gadget controller
+ *
+ * This is used by the USB gadget stack to register the gadget controller
+ * to the OTG core. Gadget controller must not be started by the
+ * caller as it is left upto the OTG state machine to do so.
+ *
+ * Gadget core must call this only when all resources required for
+ * gadget controller to run are available.
+ * i.e. gadget function driver is available.
+ *
+ * Returns: 0 on success, error value otherwise.
+ */
+int usb_otg_register_gadget(struct usb_gadget *gadget,
+			    struct otg_gadget_ops *ops)
+{
+	struct usb_otg *otg;
+	struct device *gadget_dev = &gadget->dev;
+	struct device *otg_dev = gadget->otg_dev;
+
+	if (!otg_dev)
+		return -EINVAL;	/* we're definitely not OTG */
+
+	/* we're otg but otg controller might not yet be registered */
+	mutex_lock(&otg_list_mutex);
+	otg = usb_otg_get_data(otg_dev);
+	mutex_unlock(&otg_list_mutex);
+	if (!otg) {
+		dev_dbg(gadget_dev,
+			"otg: controller not yet registered. waiting..\n");
+		/*
+		 * otg controller might register later. Put the gadget in
+		 * wait list and call us back when ready
+		 */
+		if (usb_otg_gadget_wait_add(otg_dev, gadget, ops)) {
+			dev_err(gadget_dev,
+				"otg: failed to add to gadget to wait list\n");
+			return -EINVAL;
+		}
+
+		return 0;
+	}
+
+	mutex_lock(&otg->fsm.lock);
+	if (otg->gadget) {
+		dev_err(otg_dev, "otg: gadget already registered with otg\n");
+		mutex_unlock(&otg->fsm.lock);
+		return -EINVAL;
+	}
+
+	otg->gadget = gadget;
+	otg->gadget_ops = ops;
+	dev_info(otg_dev, "otg: gadget %s registered\n",
+		 dev_name(&gadget->dev));
+
+	/* start FSM */
+	usb_otg_start_fsm(otg);
+	mutex_unlock(&otg->fsm.lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_register_gadget);
+
+/**
+ * usb_otg_unregister_gadget - Unregister the gadget controller from OTG core
+ * @gadget:	gadget controller
+ *
+ * This is used by the USB gadget stack to unregister the gadget controller
+ * from the OTG core. Ensures that gadget controller is halted
+ * on successful return.
+ *
+ * Returns: 0 on success, error value otherwise.
+ */
+int usb_otg_unregister_gadget(struct usb_gadget *gadget)
+{
+	struct usb_otg *otg;
+	struct device *gadget_dev = &gadget->dev;
+	struct device *otg_dev = gadget->otg_dev;
+
+	if (!otg_dev)
+		return -EINVAL;
+
+	mutex_lock(&otg_list_mutex);
+	otg = usb_otg_get_data(otg_dev);
+	mutex_unlock(&otg_list_mutex);
+	if (!otg) {
+		/* are we in wait list? */
+		if (!usb_otg_gadget_wait_remove(gadget))
+			return 0;
+
+		dev_dbg(gadget_dev, "otg: gadget wasn't registered with otg\n");
+		return -EINVAL;
+	}
+
+	mutex_lock(&otg->fsm.lock);
+	if (otg->gadget != gadget) {
+		dev_err(otg_dev, "otg: gadget %s wasn't registered with otg\n",
+			dev_name(&gadget->dev));
+		mutex_unlock(&otg->fsm.lock);
+		return -EINVAL;
+	}
+
+	/* Stop FSM & gadget */
+	usb_otg_stop_fsm(otg);
+	otg->gadget = NULL;
+	mutex_unlock(&otg->fsm.lock);
+
+	dev_info(otg_dev, "otg: gadget %s unregistered\n",
+		 dev_name(&gadget->dev));
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(usb_otg_unregister_gadget);
diff --git a/drivers/usb/common/usb-otg.h b/drivers/usb/common/usb-otg.h
new file mode 100644
index 0000000..2bf3fbf
--- /dev/null
+++ b/drivers/usb/common/usb-otg.h
@@ -0,0 +1,71 @@
+/**
+ * drivers/usb/common/usb-otg.h - USB OTG core local header
+ *
+ * Copyright (C) 2016 Texas Instruments Incorporated - http://www.ti.com
+ * Author: Roger Quadros <rogerq@xxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef __DRIVERS_USB_COMMON_USB_OTG_H
+#define __DRIVERS_USB_COMMON_USB_OTG_H
+
+/*
+ *  A-DEVICE timing constants
+ */
+
+/* Wait for VBUS Rise  */
+#define TA_WAIT_VRISE        (100)	/* a_wait_vrise: section 7.1.2
+					 * a_wait_vrise_tmr: section 7.4.5.1
+					 * TA_VBUS_RISE <= 100ms, section 4.4
+					 * Table 4-1: Electrical Characteristics
+					 * ->DC Electrical Timing
+					 */
+/* Wait for VBUS Fall  */
+#define TA_WAIT_VFALL        (1000)	/* a_wait_vfall: section 7.1.7
+					 * a_wait_vfall_tmr: section: 7.4.5.2
+					 */
+/* Wait for B-Connect */
+#define TA_WAIT_BCON         (10000)	/* a_wait_bcon: section 7.1.3
+					 * TA_WAIT_BCON: should be between 1100
+					 * and 30000 ms, section 5.5, Table 5-1
+					 */
+/* A-Idle to B-Disconnect */
+#define TA_AIDL_BDIS         (5000)	/* a_suspend min 200 ms, section 5.2.1
+					 * TA_AIDL_BDIS: section 5.5, Table 5-1
+					 */
+/* B-Idle to A-Disconnect */
+#define TA_BIDL_ADIS         (500)	/* TA_BIDL_ADIS: section 5.2.1
+					 * 500ms is used for B switch to host
+					 * for safe
+					 */
+
+/*
+ * B-device timing constants
+ */
+
+/* Data-Line Pulse Time*/
+#define TB_DATA_PLS          (10)	/* b_srp_init,continue 5~10ms
+					 * section:5.1.3
+					 */
+/* SRP Fail Time  */
+#define TB_SRP_FAIL          (6000)	/* b_srp_init,fail time 5~6s
+					 * section:5.1.6
+					 */
+/* A-SE0 to B-Reset  */
+#define TB_ASE0_BRST         (155)	/* minimum 155 ms, section:5.3.1 */
+/* SE0 Time Before SRP */
+#define TB_SE0_SRP           (1000)	/* b_idle,minimum 1s, section:5.1.2 */
+/* SSEND time before SRP */
+#define TB_SSEND_SRP         (1500)	/* minimum 1.5 sec, section:5.1.2 */
+
+#define TB_SESS_VLD          (1000)
+
+#endif /* __DRIVERS_USB_COMMON_USB_OTG_H */
diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
index ae228d0..b468a9f 100644
--- a/drivers/usb/core/Kconfig
+++ b/drivers/usb/core/Kconfig
@@ -42,7 +42,7 @@ config USB_DYNAMIC_MINORS
 	  If you are unsure about this, say N here.
 
 config USB_OTG
-	bool "OTG support"
+	bool "OTG/Dual-role support"
 	depends on PM
 	default n
 	help
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index 8c0ae64..1878ae1 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -583,6 +583,7 @@ struct usb_gadget_ops {
  * @out_epnum: last used out ep number
  * @in_epnum: last used in ep number
  * @otg_caps: OTG capabilities of this gadget.
+ * @otg_dev: OTG controller device, if needs to be used with OTG core.
  * @sg_supported: true if we can handle scatter-gather
  * @is_otg: True if the USB device port uses a Mini-AB jack, so that the
  *	gadget driver must provide a USB OTG descriptor.
@@ -639,6 +640,7 @@ struct usb_gadget {
 	unsigned			out_epnum;
 	unsigned			in_epnum;
 	struct usb_otg_caps		*otg_caps;
+	struct device			*otg_dev;
 
 	unsigned			sg_supported:1;
 	unsigned			is_otg:1;
diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index 861ccaa..2017cd4 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -184,6 +184,7 @@ struct usb_hcd {
 	struct mutex		*bandwidth_mutex;
 	struct usb_hcd		*shared_hcd;
 	struct usb_hcd		*primary_hcd;
+	struct device		*otg_dev;	/* OTG controller device */
 
 
 #define HCD_BUFFER_POOLS	4
diff --git a/include/linux/usb/otg-fsm.h b/include/linux/usb/otg-fsm.h
index 26e6531..943714a 100644
--- a/include/linux/usb/otg-fsm.h
+++ b/include/linux/usb/otg-fsm.h
@@ -60,6 +60,11 @@ enum otg_fsm_timer {
 /**
  * struct otg_fsm - OTG state machine according to the OTG spec
  *
+ * DRD mode hardware Inputs
+ *
+ * @id:		TRUE for B-device, FALSE for A-device.
+ * @b_sess_vld:	VBUS voltage in regulation.
+ *
  * OTG hardware Inputs
  *
  *	Common inputs for A and B device
@@ -132,6 +137,7 @@ enum otg_fsm_timer {
  * a_clr_err:	Asserted (by application ?) to clear a_vbus_err due to an
  *		overcurrent condition and causes the A-device to transition
  *		to a_wait_vfall
+ * running:	state machine running/stopped indicator
  */
 struct otg_fsm {
 	/* Input */
@@ -187,6 +193,7 @@ struct otg_fsm {
 	int b_ase0_brst_tmout;
 	int a_bidl_adis_tmout;
 
+	bool running;
 	struct otg_fsm_ops *ops;
 
 	/* Current usb protocol used: 0:undefine; 1:host; 2:client */
diff --git a/include/linux/usb/otg.h b/include/linux/usb/otg.h
index 85b8fb5..b094352 100644
--- a/include/linux/usb/otg.h
+++ b/include/linux/usb/otg.h
@@ -10,10 +10,55 @@
 #define __LINUX_USB_OTG_H
 
 #include <linux/phy/phy.h>
-#include <linux/usb/phy.h>
-#include <linux/usb/otg-fsm.h>
+#include <linux/device.h>
+#include <linux/hrtimer.h>
+#include <linux/ktime.h>
+#include <linux/usb.h>
 #include <linux/usb/hcd.h>
+#include <linux/usb/gadget.h>
+#include <linux/usb/otg-fsm.h>
+#include <linux/usb/phy.h>
 
+/**
+ * struct otg_hcd - host controller state and interface
+ *
+ * @hcd: host controller
+ * @irqnum: irq number
+ * @irqflags: irq flags
+ * @ops: otg to host controller interface
+ * @ops: otg to host controller interface
+ * @otg_dev: otg controller device
+ */
+struct otg_hcd {
+	struct usb_hcd *hcd;
+	unsigned int irqnum;
+	unsigned long irqflags;
+	struct otg_hcd_ops *ops;
+	struct device *otg_dev;
+};
+
+/**
+ * struct usb_otg - usb otg controller state
+ *
+ * @default_a: Indicates we are an A device. i.e. Host.
+ * @phy: USB phy interface
+ * @usb_phy: old usb_phy interface
+ * @host: host controller bus
+ * @gadget: gadget device
+ * @state: current otg state
+ * @dev: otg controller device
+ * @caps: otg capabilities revision, hnp, srp, etc
+ * @fsm: otg finite state machine
+ * @hcd_ops: host controller interface
+ * ------- internal use only -------
+ * @primary_hcd: primary host state and interface
+ * @shared_hcd: shared host state and interface
+ * @gadget_ops: gadget controller interface
+ * @list: list of otg controllers
+ * @work: otg state machine work
+ * @wq: otg state machine work queue
+ * @flags: to track if host/gadget is running
+ */
 struct usb_otg {
 	u8			default_a;
 
@@ -24,9 +69,24 @@ struct usb_otg {
 	struct usb_gadget	*gadget;
 
 	enum usb_otg_state	state;
+	struct device *dev;
+	struct usb_otg_caps *caps;
 	struct otg_fsm fsm;
 	struct otg_hcd_ops	*hcd_ops;
 
+	/* internal use only */
+	struct otg_hcd primary_hcd;
+	struct otg_hcd shared_hcd;
+	struct otg_gadget_ops *gadget_ops;
+	struct list_head list;
+	struct work_struct work;
+	struct workqueue_struct *wq;
+	u32 flags;
+#define OTG_FLAG_GADGET_RUNNING (1 << 0)
+#define OTG_FLAG_HOST_RUNNING (1 << 1)
+	/* use otg->fsm.lock for serializing access */
+
+/*------------- deprecated interface -----------------------------*/
 	/* bind/unbind the host controller */
 	int	(*set_host)(struct usb_otg *otg, struct usb_bus *host);
 
@@ -42,7 +102,7 @@ struct usb_otg {
 
 	/* start or continue HNP role switch */
 	int	(*start_hnp)(struct usb_otg *otg);
-
+/*---------------------------------------------------------------*/
 };
 
 /**
@@ -60,8 +120,92 @@ struct usb_otg_caps {
 	bool adp_support;
 };
 
+/**
+ * struct usb_otg_config - otg controller configuration
+ * @caps: otg capabilities of the controller
+ * @ops: otg fsm operations
+ * @otg_work: optional custom otg state machine work function
+ */
+struct usb_otg_config {
+	struct usb_otg_caps *otg_caps;
+	struct otg_fsm_ops *fsm_ops;
+	void (*otg_work)(struct work_struct *work);
+};
+
 extern const char *usb_otg_state_string(enum usb_otg_state state);
 
+#if IS_ENABLED(CONFIG_USB_OTG)
+struct usb_otg *usb_otg_register(struct device *dev,
+				 struct usb_otg_config *config);
+int usb_otg_unregister(struct device *dev);
+int usb_otg_register_hcd(struct usb_hcd *hcd, unsigned int irqnum,
+			 unsigned long irqflags, struct otg_hcd_ops *ops);
+int usb_otg_unregister_hcd(struct usb_hcd *hcd);
+int usb_otg_register_gadget(struct usb_gadget *gadget,
+			    struct otg_gadget_ops *ops);
+int usb_otg_unregister_gadget(struct usb_gadget *gadget);
+void usb_otg_sync_inputs(struct usb_otg *otg);
+int usb_otg_kick_fsm(struct device *otg_dev);
+int usb_otg_start_host(struct usb_otg *otg, int on);
+int usb_otg_start_gadget(struct usb_otg *otg, int on);
+
+#else /* CONFIG_USB_OTG */
+
+static inline struct usb_otg *usb_otg_register(struct device *dev,
+					       struct usb_otg_config *config)
+{
+	return ERR_PTR(-ENOTSUPP);
+}
+
+static inline int usb_otg_unregister(struct device *dev)
+{
+	return -ENOTSUPP;
+}
+
+static inline int usb_otg_register_hcd(struct usb_hcd *hcd, unsigned int irqnum,
+				       unsigned long irqflags,
+				       struct otg_hcd_ops *ops)
+{
+	return -ENOTSUPP;
+}
+
+static inline int usb_otg_unregister_hcd(struct usb_hcd *hcd)
+{
+	return -ENOTSUPP;
+}
+
+static inline int usb_otg_register_gadget(struct usb_gadget *gadget,
+					  struct otg_gadget_ops *ops)
+{
+	return -ENOTSUPP;
+}
+
+static inline int usb_otg_unregister_gadget(struct usb_gadget *gadget)
+{
+	return -ENOTSUPP;
+}
+
+static inline void usb_otg_sync_inputs(struct usb_otg *otg)
+{
+}
+
+static inline int usb_otg_kick_fsm(struct device *otg_dev)
+{
+	return -ENOTSUPP;
+}
+
+static inline int usb_otg_start_host(struct usb_otg *otg, int on)
+{
+	return -ENOTSUPP;
+}
+
+static inline int usb_otg_start_gadget(struct usb_otg *otg, int on)
+{
+	return -ENOTSUPP;
+}
+#endif /* CONFIG_USB_OTG */
+
+/*------------- deprecated interface -----------------------------*/
 /* Context: can sleep */
 static inline int
 otg_start_hnp(struct usb_otg *otg)
@@ -113,6 +257,8 @@ otg_start_srp(struct usb_otg *otg)
 	return -ENOTSUPP;
 }
 
+/*---------------------------------------------------------------*/
+
 /* for OTG controller drivers (and maybe other stuff) */
 extern int usb_bus_start_enum(struct usb_bus *bus, unsigned port_num);
 
@@ -237,4 +383,6 @@ static inline int otg_start_gadget(struct usb_otg *otg, int on)
 	return otg->fsm.ops->start_gadget(otg, on);
 }
 
+int drd_statemachine(struct usb_otg *otg);
+
 #endif /* __LINUX_USB_OTG_H */
-- 
2.7.4