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Date:	Thu, 19 Mar 2015 11:40:35 +0800
From:	Peter Chen <peter.chen@...escale.com>
To:	Roger Quadros <rogerq@...com>
CC:	<gregkh@...uxfoundation.org>, <balbi@...com>,
	<stern@...land.harvard.edu>, <dan.j.williams@...el.com>,
	<jun.li@...escale.com>, <mathias.nyman@...ux.intel.com>,
	<linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-omap@...r.kernel.org>
Subject: Re: [RFC][PATCH 3/9] usb: otg: add OTG core

On Wed, Mar 18, 2015 at 03:55:57PM +0200, Roger Quadros wrote:
> The OTG core instantiates the OTG Finite State Machine
> per OTG controller and manages starting/stopping the
> host and gadget controllers based on the bus state.
> 
> It provides APIs for the following tasks
> 
> - Registering an OTG capable controller
> - Registering Host and Gadget controllers to OTG core
> - Providing inputs to and kicking the OTG state machine
> 
> TODO:
> - sysfs interface to allow application inputs to OTG state machine
> - otg class?
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  drivers/usb/Makefile         |   1 +
>  drivers/usb/common/Makefile  |   1 +
>  drivers/usb/common/usb-otg.c | 732 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/usb/common/usb-otg.h |  71 +++++
>  drivers/usb/core/Kconfig     |   8 +
>  include/linux/usb/usb-otg.h  |  86 +++++
>  6 files changed, 899 insertions(+)
>  create mode 100644 drivers/usb/common/usb-otg.c
>  create mode 100644 drivers/usb/common/usb-otg.h
>  create mode 100644 include/linux/usb/usb-otg.h
> 
> diff --git a/drivers/usb/Makefile b/drivers/usb/Makefile
> index 2f1e2aa..07f59a5 100644
> --- a/drivers/usb/Makefile
> +++ b/drivers/usb/Makefile
> @@ -60,5 +60,6 @@ obj-$(CONFIG_USB_RENESAS_USBHS)	+= renesas_usbhs/
>  obj-$(CONFIG_USB_GADGET)	+= gadget/
>  
>  obj-$(CONFIG_USB_COMMON)	+= common/
> +obj-$(CONFIG_USB_OTG_CORE)	+= common/
>  
>  obj-$(CONFIG_USBIP_CORE)	+= usbip/
> diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
> index ca2f8bd..573fc75 100644
> --- a/drivers/usb/common/Makefile
> +++ b/drivers/usb/common/Makefile
> @@ -7,3 +7,4 @@ usb-common-y			  += common.o
>  usb-common-$(CONFIG_USB_LED_TRIG) += led.o
>  
>  obj-$(CONFIG_USB_OTG_FSM) += usb-otg-fsm.o
> +obj-$(CONFIG_USB_OTG_CORE) += usb-otg.o
> diff --git a/drivers/usb/common/usb-otg.c b/drivers/usb/common/usb-otg.c
> new file mode 100644
> index 0000000..1433fc9
> --- /dev/null
> +++ b/drivers/usb/common/usb-otg.c
> @@ -0,0 +1,732 @@
> +/**
> + * drivers/usb/common/usb-otg.c - USB OTG core
> + *
> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com
> + * Author: Roger Quadros <rogerq@...com>
> + *
> + * 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/list.h>
> +#include <linux/timer.h>
> +#include <linux/usb/otg.h>
> +#include <linux/usb/phy.h>	/* enum usb_otg_state */
> +#include <linux/usb/gadget.h>
> +#include <linux/usb/usb-otg.h>
> +#include <linux/workqueue.h>
> +
> +#include "usb-otg.h"
> +
> +/* to link timer with callback data */
> +struct otg_timer {
> +	struct timer_list timer;
> +	/* callback data */
> +	int *timeout_bit;
> +	struct otg_data *otgd;
> +};
> +
> +struct otg_data {
> +	struct device *dev;	/* HCD & GCD's parent device */
> +
> +	struct otg_fsm fsm;
> +	/* HCD, GCD and usb_otg_state are present in otg_fsm->otg
> +	 * HCD is bus_to_hcd(fsm->otg->host)
> +	 * GCD is fsm->otg->gadget
> +	 */
> +	struct otg_fsm_ops fsm_ops;	/* private copy for override */
> +	struct usb_otg otg;
> +	struct usb_hcd *shared_hcd;	/* if shared HCD registered */
> +
> +	/* saved hooks to OTG device */
> +	int (*start_host)(struct otg_fsm *fsm, int on);
> +	int (*start_gadget)(struct otg_fsm *fsm, int on);
> +
> +	struct list_head list;
> +
> +	struct work_struct work;	/* OTG FSM work */
> +	struct workqueue_struct *wq;
> +
> +	struct otg_timer timers[NUM_OTG_FSM_TIMERS];
> +
> +	bool fsm_running;
> +	bool gadget_can_start;		/* OTG FSM says gadget can start */
> +	bool host_can_start;		/* OTG FSM says host can start */
> +
> +	/* use otg->fsm.lock for serializing access */
> +};

What's the relationship between struct usb_otg otg and this one?

> +
> +/* OTG device list */
> +LIST_HEAD(otg_list);
> +static DEFINE_MUTEX(otg_list_mutex);
> +
> +/**
> + * check if device is in our OTG list and return
> + * otg_data, else NULL.
> + *
> + * otg_list_mutex must be held.
> + */
> +static struct otg_data *usb_otg_device_get_otgd(struct device *parent_dev)
> +{
> +	struct otg_data *otgd;
> +
> +	list_for_each_entry(otgd, &otg_list, list) {
> +		if (otgd->dev == parent_dev)
> +			return otgd;
> +	}
> +
> +	return NULL;
> +}
> +
> +/**
> + * timer callback to set timeout bit and kick FSM
> + */
> +static void set_tmout(unsigned long data)
> +{
> +	struct otg_timer *tmr_data;
> +
> +	tmr_data = (struct otg_timer *)data;
> +
> +	if (tmr_data->timeout_bit)
> +		*tmr_data->timeout_bit = 1;
> +
> +	usb_otg_sync_inputs(&tmr_data->otgd->fsm);
> +}
> +
> +/**
> + * Initialize one OTG timer with callback, timeout and timeout bit
> + */
> +static void otg_timer_init(enum otg_fsm_timer id, struct otg_data *otgd,
> +			   void (*callback)(unsigned long),
> +			   unsigned long expires_ms,
> +			   int *timeout_bit)
> +{
> +	struct otg_timer *otgtimer = &otgd->timers[id];
> +	struct timer_list *timer = &otgtimer->timer;
> +
> +	init_timer(timer);
> +	timer->function = callback;
> +	timer->expires = jiffies + msecs_to_jiffies(expires_ms);
> +	timer->data = (unsigned long)otgtimer;
> +

The timer for TB_DATA_PLS is about 10ms or less, it is not suitable
for using kernel timer, hrtimer is suitable choice.

> +	otgtimer->timeout_bit = timeout_bit;
> +	otgtimer->otgd = otgd;
> +}
> +
> +/**
> + * Initialize standard OTG timers
> + */
> +static void usb_otg_init_timers(struct otg_data *otgd)
> +{
> +	struct otg_fsm *fsm = &otgd->fsm;
> +
> +	otg_timer_init(A_WAIT_VRISE, otgd, set_tmout, TA_WAIT_VRISE, &fsm->a_wait_vrise_tmout);
> +	otg_timer_init(A_WAIT_VFALL, otgd, set_tmout, TA_WAIT_VFALL, &fsm->a_wait_vfall_tmout);
> +	otg_timer_init(A_WAIT_BCON, otgd, set_tmout, TA_WAIT_BCON, &fsm->a_wait_bcon_tmout);
> +	otg_timer_init(A_AIDL_BDIS, otgd, set_tmout, TA_AIDL_BDIS, &fsm->a_aidl_bdis_tmout);
> +	otg_timer_init(A_BIDL_ADIS, otgd, set_tmout, TA_BIDL_ADIS, &fsm->a_bidl_adis_tmout);
> +	otg_timer_init(B_ASE0_BRST, otgd, set_tmout, TB_ASE0_BRST, &fsm->b_ase0_brst_tmout);
> +
> +	otg_timer_init(B_SE0_SRP, otgd, set_tmout, TB_SE0_SRP, &fsm->b_se0_srp);
> +	otg_timer_init(B_SRP_FAIL, otgd, set_tmout, TB_SRP_FAIL, &fsm->b_srp_done);
> +
> +	otg_timer_init(A_WAIT_ENUM, otgd, set_tmout, TB_SRP_FAIL, NULL);
> +}
> +
> +/**
> + * OTG FSM ops function to add timer
> + */
> +static void usb_otg_add_timer(struct otg_fsm *fsm, enum otg_fsm_timer id)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +	struct timer_list *timer = &otgd->timers[id].timer;
> +
> +	if (!otgd->fsm_running)
> +		return;
> +
> +	/* if timer is already active, exit */
> +	if (timer_pending(timer)) {
> +		dev_err(otgd->dev, "USB-OTG: Timer %d is already running\n",
> +			id);
> +	}
> +
> +	add_timer(timer);
> +}
> +
> +/**
> + * OTG FSM ops function to delete timer
> + */
> +static void usb_otg_del_timer(struct otg_fsm *fsm, enum otg_fsm_timer id)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +	struct timer_list *timer = &otgd->timers[id].timer;
> +
> +	del_timer(timer);
> +}
> +
> +/**
> + * OTG FSM ops function to start/stop host
> + */
> +static int usb_otg_start_host(struct otg_fsm *fsm, int on)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +	int ret = 0;
> +	struct usb_hcd *hcd;
> +
> +	dev_info(otgd->dev, "%s %d\n", __func__, on);
> +	if (!fsm->otg->host) {
> +		WARN_ONCE(1, "OTG FSM running without Host\n");
> +		return 0;
> +	}
> +
> +	hcd = bus_to_hcd(fsm->otg->host);
> +	otgd->host_can_start = on;
> +	if (hcd->shared_hcd && !otgd->shared_hcd) {
> +		dev_info(otgd->dev, "%s: waiting for Shared HCD to register\n",
> +			 __func__);
> +		return 0;
> +	}
> +
> +	/* call OTG device operations */
> +	if (otgd->start_host) {
> +		ret = otgd->start_host(fsm, on);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (on) {
> +		usb_start_hcd(hcd);
> +		if (hcd->shared_hcd)
> +			usb_start_hcd(hcd->shared_hcd);
> +	} else {
> +		if (hcd->shared_hcd)
> +			usb_stop_hcd(hcd->shared_hcd);
> +		usb_stop_hcd(hcd);
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * OTG FSM ops function to start/stop gadget
> + */
> +static int usb_otg_start_gadget(struct otg_fsm *fsm, int on)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +	int ret = 0;
> +	struct usb_gadget *gadget = fsm->otg->gadget;
> +
> +	dev_info(otgd->dev, "%s %d\n", __func__, on);
> +	if (!gadget) {
> +		WARN_ONCE(1, "OTG FSM running without Gadget\n");
> +		return 0;
> +	}
> +
> +	/* call OTG device operations */
> +	if (otgd->start_gadget) {
> +		ret = otgd->start_gadget(fsm, on);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	otgd->gadget_can_start = on;
> +	if (on)
> +		usb_gadget_start(fsm->otg->gadget);
> +	else
> +		usb_gadget_stop(fsm->otg->gadget);
> +
> +	return 0;
> +}
> +
> +/**
> + * OTG FSM work function
> + */
> +static void usb_otg_work(struct work_struct *work)
> +{
> +	struct otg_data *otgd = container_of(work, struct otg_data, work);
> +
> +	if (otg_statemachine(&otgd->fsm)) {
> +		/* state changed. any action ? */
> +	}
> +}
> +
> +/**
> + * usb_otg_register() - Register the OTG device to OTG core
> + * @parent_device:	parent device of Host & Gadget controllers.
> + * @otg_fsm_ops:	otg state machine ops.
> + *
> + * Register parent device that contains both HCD and GCD into
> + * the USB OTG core. HCD and GCD will be prevented from starting
> + * till both are available for use.
> + *
> + * Return: struct otg_fsm * if success, NULL if error.
> + */
> +struct otg_fsm *usb_otg_register(struct device *parent_dev,
> +				 struct otg_fsm_ops *fsm_ops)
> +{
> +	struct otg_data *otgd;
> +	int ret = 0;
> +
> +	if (!parent_dev || !fsm_ops)
> +		return ERR_PTR(-EINVAL);
> +
> +	/* already in list? */
> +	mutex_lock(&otg_list_mutex);
> +	if (usb_otg_device_get_otgd(parent_dev)) {
> +		dev_err(parent_dev, "%s: device already in OTG list\n",
> +			__func__);
> +		ret = -EINVAL;
> +		goto unlock;
> +	}
> +
> +	/* allocate and add to list */
> +	otgd = kzalloc(sizeof(*otgd), GFP_KERNEL);
> +	if (!otgd) {
> +		ret = -ENOMEM;
> +		goto unlock;
> +	}
> +
> +	otgd->dev = parent_dev;
> +	INIT_WORK(&otgd->work, usb_otg_work);
> +	otgd->wq = create_singlethread_workqueue("usb_otg");
> +	if (!otgd->wq) {
> +		dev_err(parent_dev, "%s: can't create workqueue\n", __func__);
> +		ret = -ENODEV;
> +		goto err_wq;
> +	}
> +
> +	usb_otg_init_timers(otgd);
> +
> +	/* save original start host/gadget ops */
> +	otgd->start_host = fsm_ops->start_host;
> +	otgd->start_gadget = fsm_ops->start_gadget;
> +	/* create copy of original ops */
> +	otgd->fsm_ops = *fsm_ops;
> +	/* override ops */
> +	otgd->fsm_ops.start_host = usb_otg_start_host;
> +	otgd->fsm_ops.start_gadget = usb_otg_start_gadget;
> +	/* FIXME: we ignore caller's timer ops */
> +	otgd->fsm_ops.add_timer = usb_otg_add_timer;
> +	otgd->fsm_ops.del_timer = usb_otg_del_timer;
> +	/* set otg ops */
> +	otgd->fsm.ops = &otgd->fsm_ops;
> +	otgd->fsm.otg = &otgd->otg;
> +
> +	mutex_init(&otgd->fsm.lock);
> +
> +	list_add_tail(&otgd->list, &otg_list);
> +	mutex_unlock(&otg_list_mutex);
> +	return &otgd->fsm;
> +
> +err_wq:
> +	kfree(otgd);
> +unlock:
> +	mutex_unlock(&otg_list_mutex);
> +	return ERR_PTR(ret);
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_register);
> +
> +/**
> + * usb_otg_unregister() - Unregister the OTG device from USB OTG core
> + * @parent_device:	parent device of Host & Gadget controllers.
> + *
> + * Unregister parent OTG deviced from USB OTG core.
> + * Prevents unregistering till both Host and Gadget controllers
> + * have unregistered from the OTG core.
> + *
> + * Return: 0 on success, error value otherwise.
> + */
> +int usb_otg_unregister(struct device *parent_dev)
> +{
> +	struct otg_data *otgd;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(parent_dev);
> +	if (!otgd) {
> +		dev_err(parent_dev, "%s: device not in OTG list\n",
> +			__func__);
> +		mutex_unlock(&otg_list_mutex);
> +		return -EINVAL;
> +	}
> +
> +	/* prevent unregister till both host & gadget have unregistered */
> +	if (otgd->fsm.otg->host || otgd->fsm.otg->gadget) {
> +		dev_err(parent_dev, "%s: host/gadget still registered\n",
> +			__func__);
> +		return -EBUSY;
> +	}
> +
> +	/* OTG FSM is halted when host/gadget unregistered */
> +	destroy_workqueue(otgd->wq);
> +
> +	/* remove from otg list */
> +	list_del(&otgd->list);
> +	kfree(otgd);
> +	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 otg_fsm *fsm)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +
> +	if (otgd->fsm_running)
> +		goto kick_fsm;
> +
> +	if (!fsm->otg->host) {
> +		dev_info(otgd->dev, "Not starting OTG till Host registers\n");
> +		return;
> +	}
> +
> +	if (!fsm->otg->gadget) {
> +		dev_info(otgd->dev, "Not starting OTG till Gadget registers\n");
> +		return;
> +	}
> +
> +	otgd->fsm_running = true;
> +kick_fsm:
> +	queue_work(otgd->wq, &otgd->work);
> +}
> +
> +/**
> + * stop the OTG FSM. Stops Host & Gadget controllers as well.
> + * fsm->lock must be held
> + */
> +static void usb_otg_stop_fsm(struct otg_fsm *fsm)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +	int i;
> +
> +	if (!otgd->fsm_running)
> +		return;
> +
> +	/* no more new events queued */
> +	otgd->fsm_running = false;
> +
> +	/* Stop state machine / timers */
> +	for (i = 0; i < ARRAY_SIZE(otgd->timers); i++)
> +		del_timer_sync(&otgd->timers[i].timer);
> +
> +	flush_workqueue(otgd->wq);
> +
> +	/* stop host/gadget immediately */
> +	if (fsm->protocol == PROTO_HOST)
> +		otg_start_host(fsm, 0);
> +	else if (fsm->protocol == PROTO_GADGET)
> +		otg_start_gadget(fsm, 0);
> +}
> +
> +/**
> + * 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 otg_fsm *fsm)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +
> +	/* Don't kick FSM till it has started */
> +	if (!otgd->fsm_running)
> +		return;
> +
> +	/* Kick FSM */
> +	queue_work(otgd->wq, &otgd->work);
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_sync_inputs);
> +
> +/**
> + * usb_otg_kick_fsm - Kick the OTG state machine
> + * @hcd_gcd_device:	Host/Gadget 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 *hcd_gcd_device)
> +{
> +	struct otg_data *otgd;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(hcd_gcd_device->parent);
> +	if (!otgd) {
> +		dev_err(hcd_gcd_device, "%s: invalid host/gadget device\n",
> +			__func__);
> +		mutex_unlock(&otg_list_mutex);
> +		return -ENODEV;
> +	}
> +
> +	mutex_unlock(&otg_list_mutex);
> +	usb_otg_sync_inputs(&otgd->fsm);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_kick_fsm);
> +
> +/**
> + * usb_otg_register_hcd - Register Host controller to OTG core
> + * @hcd:	Host controller device
> + *
> + * 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.
> + *
> + * Returns: 0 on success, error value otherwise.
> + */
> +int usb_otg_register_hcd(struct usb_hcd *hcd)
> +{
> +	struct otg_data *otgd;
> +	struct usb_bus *bus = hcd_to_bus(hcd);
> +	struct device *otg_dev = bus->controller->parent;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(otg_dev);
> +	if (!otgd) {
> +		dev_err(otg_dev, "%s: device not registered to OTG core\n",
> +			__func__);
> +		mutex_unlock(&otg_list_mutex);
> +		return -EINVAL;
> +	}
> +
> +	mutex_unlock(&otg_list_mutex);
> +	/* HCD will be started by OTG fsm when needed */
> +	mutex_lock(&otgd->fsm.lock);
> +	if (otgd->fsm.otg->host) {
> +		/* probably a shared hcd ? */
> +		if (usb_hcd_is_primary_hcd(hcd)) {
> +			dev_err(otg_dev, "%s: hcd already registered\n",
> +				__func__);
> +			goto err;
> +		}
> +
> +		if (hcd->shared_hcd == bus_to_hcd(otgd->fsm.otg->host)) {
> +			if (otgd->shared_hcd) {
> +				dev_err(otg_dev, "%s: shared HCD already registered\n",
> +					__func__);
> +				goto err;
> +			}
> +
> +			otgd->shared_hcd = hcd;
> +			dev_info(otg_dev, "USB-OTG: Shared Host %s registered\n",
> +				 dev_name(bus->controller));
> +			/* we might be pending a start_host */
> +			if (otgd->host_can_start)
> +				usb_otg_start_host(&otgd->fsm, 1);
> +			goto unlock;
> +		} else {
> +			dev_err(otg_dev, "%s: invalid shared hcd\n",
> +					__func__);
> +			goto err;
> +		}
> +	}
> +
> +	otgd->fsm.otg->host = bus;
> +
> +	/* FIXME: set bus->otg_port if this is true OTG port with HNP */
> +	dev_info(otg_dev, "USB-OTG: Primary Host %s registered\n",
> +		 dev_name(bus->controller));
> +
> +unlock:
> +	/* Kick FSM */
> +	usb_otg_start_fsm(&otgd->fsm);
> +	mutex_unlock(&otgd->fsm.lock);
> +
> +	return 0;
> +
> +err:
> +	mutex_unlock(&otgd->fsm.lock);
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_register_hcd);
> +
> +/**
> + * usb_otg_unregister_hcd - Unregister 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 otg_data *otgd;
> +	struct usb_bus *bus = hcd_to_bus(hcd);
> +	struct device *otg_dev = bus->controller->parent;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(otg_dev);
> +	if (!otgd) {
> +		dev_err(otg_dev, "%s: device not registered to OTG core\n",
> +			__func__);
> +		mutex_unlock(&otg_list_mutex);
> +		return -EINVAL;
> +	}
> +
> +	mutex_unlock(&otg_list_mutex);
> +
> +	mutex_lock(&otgd->fsm.lock);
> +	if (otgd->fsm.otg->host != bus) {
> +		dev_err(otg_dev, "%s: host wansn't registered with OTG\n",
> +			__func__);
> +		mutex_unlock(&otgd->fsm.lock);
> +		return -EINVAL;
> +	}
> +
> +	/* stop FSM & Host */
> +	usb_otg_stop_fsm(&otgd->fsm);
> +	otgd->fsm.otg->host = NULL;
> +
> +	mutex_unlock(&otgd->fsm.lock);
> +	dev_info(otg_dev, "USB-OTG: Host %s unregistered\n",
> +		 dev_name(bus->controller));
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_unregister_hcd);
> +
> +/**
> + * usb_otg_register_gadget - Register 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.
> + *
> + * As gadget controller needs to be prevented from starting till other
> + * conditions are met (i.e. driver loaded, softconnet enabled),
> + * the gadget stack can use the usb_otg_gadget_can_start() function
> + * to check if OTG core has given the permission to start the gadget.
> + *
> + * Returns: 0 on success, error value otherwise.
> + */
> +int usb_otg_register_gadget(struct usb_gadget *gadget)
> +{
> +	struct otg_data *otgd;
> +	struct device *otg_dev = gadget->dev.parent;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(otg_dev);
> +	if (!otgd) {
> +		dev_err(otg_dev, "%s: device not registered to OTG core\n",
> +			__func__);
> +		mutex_unlock(&otg_list_mutex);
> +		return -EINVAL;
> +	}
> +
> +	mutex_unlock(&otg_list_mutex);
> +
> +	mutex_lock(&otgd->fsm.lock);
> +	if (otgd->fsm.otg->gadget) {
> +		dev_err(otg_dev, "%s: gadget already registered with OTG\n",
> +			__func__);
> +		mutex_unlock(&otgd->fsm.lock);
> +		return -EINVAL;
> +	}
> +
> +	otgd->fsm.otg->gadget = gadget;
> +	dev_info(otg_dev, "USB-OTG: Gadget %s registered\n",
> +		 dev_name(&gadget->dev));
> +
> +	/* Kick FSM */
> +	usb_otg_start_fsm(&otgd->fsm);
> +	mutex_unlock(&otgd->fsm.lock);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_register_gadget);
> +
> +/**
> + * usb_otg_unregister_gadget - Unregister 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 not running
> + * on successful return.
> + *
> + * Returns: 0 on success, error value otherwise.
> + */
> +int usb_otg_unregister_gadget(struct usb_gadget *gadget)
> +{
> +	struct otg_data *otgd;
> +	struct device *otg_dev = gadget->dev.parent;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(otg_dev);
> +	if (!otgd) {
> +		dev_err(otg_dev, "%s: device not registered to OTG core\n",
> +			__func__);
> +		mutex_unlock(&otg_list_mutex);
> +		return -EINVAL;
> +	}
> +
> +	mutex_unlock(&otg_list_mutex);
> +
> +	mutex_lock(&otgd->fsm.lock);
> +	if (otgd->fsm.otg->gadget != gadget) {
> +		dev_err(otg_dev, "%s: gadget wasn't registered with OTG\n",
> +			__func__);
> +		mutex_unlock(&otgd->fsm.lock);
> +		return -EINVAL;
> +	}
> +
> +	/* Stop FSM & gadget */
> +	usb_otg_stop_fsm(&otgd->fsm);
> +	otgd->fsm.otg->gadget = NULL;
> +	mutex_unlock(&otgd->fsm.lock);
> +
> +	dev_info(otg_dev, "USB-OTG: Gadget %s unregistered\n",
> +		 dev_name(&gadget->dev));
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_unregister_gadget);
> +
> +/**
> + * usb_otg_gadget_can_start - check if Gadget can be started from OTG perspective
> + * @gadget:	Gadget controller
> + *
> + * This is used by the USB Gadget stack to check if Gadget controller
> + * can be started from the OTG state machines perspective.
> + * i.e. we're in 'b_peripheral' state.
> + *
> + * Returns: 0 on success, error value otherwise.
> + */
> +bool usb_otg_gadget_can_start(struct usb_gadget *gadget)
> +{
> +	struct otg_data *otgd;
> +	struct device *otg_dev = gadget->dev.parent;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(otg_dev);
> +	if (!otgd) {
> +		dev_err(otg_dev, "%s: device not registered to OTG core\n",
> +			__func__);
> +		mutex_unlock(&otg_list_mutex);
> +		return -EINVAL;
> +	}
> +
> +	mutex_unlock(&otg_list_mutex);
> +
> +	return otgd->gadget_can_start;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_gadget_can_start);
> diff --git a/drivers/usb/common/usb-otg.h b/drivers/usb/common/usb-otg.h
> new file mode 100644
> index 0000000..05331f0
> --- /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) 2015 Texas Instruments Incorporated - http://www.ti.com
> + * Author: Roger Quadros <rogerq@...com>
> + *
> + * 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 cc0ced0..43a0d2d 100644
> --- a/drivers/usb/core/Kconfig
> +++ b/drivers/usb/core/Kconfig
> @@ -84,3 +84,11 @@ config USB_OTG_FSM
>  	  Implements OTG Finite State Machine as specified in On-The-Go
>  	  and Embedded Host Supplement to the USB Revision 2.0 Specification.
>  
> +config USB_OTG_CORE
> +	tristate "USB OTG core"
> +	depends on USB
> +	select USB_OTG_FSM
> +	help
> +	  Standardize the way OTG is implemented on Linux. The OTG state
> +	  machine is instantiated here instead of being done in each controller
> +	  driver.
> diff --git a/include/linux/usb/usb-otg.h b/include/linux/usb/usb-otg.h
> new file mode 100644
> index 0000000..52ab7b1
> --- /dev/null
> +++ b/include/linux/usb/usb-otg.h
> @@ -0,0 +1,86 @@
> +/**
> + * include/linux/usb/usb-otg.h - USB OTG core
> + *
> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com
> + * Author: Roger Quadros <rogerq@...com>
> + *
> + * 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 __LINUX_USB_OTG_CORE_H
> +#define __LINUX_USB_OTG_CORE_H
> +
> +#include <linux/device.h>
> +#include <linux/usb.h>
> +#include <linux/usb/hcd.h>
> +#include <linux/usb/gadget.h>
> +#include <linux/usb/otg-fsm.h>
> +
> +#if IS_ENABLED(CONFIG_USB_OTG_CORE)
> +struct otg_fsm *usb_otg_register(struct device *parent_dev,
> +				 struct otg_fsm_ops *fsm_ops);
> +int usb_otg_unregister(struct device *parent_dev);
> +int usb_otg_register_hcd(struct usb_hcd *hcd);
> +int usb_otg_unregister_hcd(struct usb_hcd *hcd);
> +int usb_otg_register_gadget(struct usb_gadget *gadget);
> +int usb_otg_unregister_gadget(struct usb_gadget *gadget);
> +void usb_otg_sync_inputs(struct otg_fsm *fsm);
> +int usb_otg_kick_fsm(struct device *hcd_gcd_device);
> +bool usb_otg_gadget_can_start(struct usb_gadget *gadget);
> +
> +#else /* CONFIG_USB_OTG_CORE */
> +
> +static inline struct otg_fsm *usb_otg_register(struct device *parent_dev,
> +					       struct otg_fsm_ops *fsm_ops)
> +{
> +	return ERR_PTR(-ENOSYS);
> +}
> +
> +static inline int usb_otg_unregister(struct device *parent_dev)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int usb_otg_register_hcd(struct usb_hcd *hcd)
> +{
> +	return -ENOSYS;
> +}
> +
> +int usb_otg_unregister_hcd(struct usb_hcd *hcd)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int usb_otg_register_gadget(struct usb_gadget *gadget)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int usb_otg_unregister_gadget(struct usb_gadget *gadget)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline void usb_otg_sync_inputs(struct otg_fsm *fsm)
> +{
> +}
> +
> +int usb_otg_kick_fsm(struct device *hcd_gcd_device)
> +{
> +	return -ENOSYS;
> +}
> +
> +bool usb_otg_gadget_can_start(struct usb_gadget *gadget)
> +{
> +	return true;
> +}
> +#endif /* CONFIG_USB_OTG_CORE */
> +
> +#endif /* __LINUX_USB_OTG_CORE */
> -- 
> 2.1.0
> 

-- 

Best Regards,
Peter Chen
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