Date: Fri, 17 Jul 2015 15:48:35 +0800
From: Li Jun <b47624@freescale.com>
To: Roger Quadros <rogerq@ti.com>
CC: <stern@rowland.harvard.edu>, <balbi@ti.com>, <gregkh@linuxfoundation.org>,
        <peter.chen@freescale.com>, <dan.j.williams@intel.com>,
        <jun.li@freescale.com>, <mathias.nyman@linux.intel.com>,
        <tony@atomide.com>, <Joao.Pinto@synopsys.com>,
        <linux-usb@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <linux-omap@vger.kernel.org>
Subject: Re: [PATCH v3 07/11] usb: otg: add OTG core
Message-ID: <20150717074832.GA4515@shlinux2>
References: <1436350777-28056-1-git-send-email-rogerq@ti.com>
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Hi, Roger

On Wed, Jul 08, 2015 at 01:19:33PM +0300, 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
> 
> Signed-off-by: Roger Quadros <rogerq@ti.com>
> ---
>  MAINTAINERS                  |   4 +-
>  drivers/usb/Kconfig          |   2 +-
>  drivers/usb/Makefile         |   1 +
>  drivers/usb/common/Makefile  |   3 +-
>  drivers/usb/common/usb-otg.c | 768 +++++++++++++++++++++++++++++++++++++++++++
>  drivers/usb/common/usb-otg.h |  71 ++++
>  drivers/usb/core/Kconfig     |  11 +-
>  include/linux/usb/otg.h      |  91 ++++-
>  8 files changed, 930 insertions(+), 21 deletions(-)
>  create mode 100644 drivers/usb/common/usb-otg.c
>  create mode 100644 drivers/usb/common/usb-otg.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 8133cef..b21278e 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -10640,12 +10640,14 @@ S:	Maintained
>  F:	Documentation/usb/ohci.txt
>  F:	drivers/usb/host/ohci*
>  
> -USB OTG FSM (Finite State Machine)
> +USB OTG/DRD core and FSM (Finite State Machine)
>  M:	Peter Chen <Peter.Chen@freescale.com>
> +M:	Roger Quadros <rogerq@ti.com>
>  T:	git git://git.kernel.org/pub/scm/linux/kernel/git/peter.chen/usb.git
>  L:	linux-usb@vger.kernel.org
>  S:	Maintained
>  F:	drivers/usb/common/usb-otg-fsm.c
> +F:	drivers/usb/common/usb-otg.c
>  
>  USB OVER IP DRIVER
>  M:	Valentina Manea <valentina.manea.m@gmail.com>
> diff --git a/drivers/usb/Kconfig b/drivers/usb/Kconfig
> index 8ed451d..5b625e2 100644
> --- a/drivers/usb/Kconfig
> +++ b/drivers/usb/Kconfig
> @@ -32,7 +32,7 @@ if USB_SUPPORT
>  config USB_COMMON
>  	tristate
>  	default y
> -	depends on USB || USB_GADGET
> +	depends on USB || USB_GADGET || USB_OTG
>  
>  config USB_ARCH_HAS_HCD
>  	def_bool y
> diff --git a/drivers/usb/Makefile b/drivers/usb/Makefile
> index d8926c6..769d13b 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)		+= common/
>  
>  obj-$(CONFIG_USBIP_CORE)	+= usbip/
> diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
> index 6bbb3ec..730d928 100644
> --- a/drivers/usb/common/Makefile
> +++ b/drivers/usb/common/Makefile
> @@ -6,5 +6,6 @@ obj-$(CONFIG_USB_COMMON)	  += usb-common.o
>  usb-common-y			  += common.o
>  usb-common-$(CONFIG_USB_LED_TRIG) += led.o
>  
> -obj-$(CONFIG_USB_OTG_FSM) += usb-otg-fsm.o
>  obj-$(CONFIG_USB_ULPI_BUS)	+= ulpi.o
> +usbotg-y		:= usb-otg.o usb-otg-fsm.o
> +obj-$(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..0379034
> --- /dev/null
> +++ b/drivers/usb/common/usb-otg.c
> @@ -0,0 +1,768 @@
> +/**
> + * drivers/usb/common/usb-otg.c - USB OTG core
> + *
> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com
> + * Author: Roger Quadros <rogerq@ti.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/ktime.h>
> +#include <linux/hrtimer.h>
> +#include <linux/list.h>
> +#include <linux/usb/otg.h>
> +#include <linux/usb/phy.h>	/* enum usb_otg_state */
> +#include <linux/usb/gadget.h>
> +#include <linux/workqueue.h>
> +
> +#include "usb-otg.h"
> +
> +/* to link timer with callback data */
> +struct otg_timer {
> +	struct hrtimer timer;
> +	ktime_t timeout;
> +	/* callback data */
> +	int *timeout_bit;
> +	struct otg_data *otgd;
> +};
> +
> +struct otg_hcd {
> +	struct usb_hcd *hcd;
> +	unsigned int irqnum;
> +	unsigned long irqflags;
> +	struct otg_hcd_ops *ops;
> +};
> +
> +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;		/* allocator for fsm->otg */
> +
> +	struct otg_hcd primary_hcd;
> +	struct otg_hcd shared_hcd;
> +
> +	struct otg_gadget_ops *gadget_ops; /* interface to gadget f/w */
> +
> +	/* 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;
> +	/* use otg->fsm.lock for serializing access */
> +};
> +
> +/* OTG device list */
> +LIST_HEAD(otg_list);
> +static DEFINE_MUTEX(otg_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 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 enum hrtimer_restart set_tmout(struct hrtimer *data)
> +{
> +	struct otg_timer *otgtimer;
> +
> +	otgtimer = container_of(data, struct otg_timer, timer);
> +	if (otgtimer->timeout_bit)
> +		*otgtimer->timeout_bit = 1;
> +
> +	usb_otg_sync_inputs(&otgtimer->otgd->fsm);
> +
> +	return HRTIMER_NORESTART;
> +}
> +
> +/**
> + * Initialize one OTG timer with callback, timeout and timeout bit
> + */
> +static void otg_timer_init(enum otg_fsm_timer id, struct otg_data *otgd,
> +			   enum hrtimer_restart (*callback)(struct hrtimer *),
> +			   unsigned long expires_ms,
> +			   int *timeout_bit)
> +{
> +	struct otg_timer *otgtimer = &otgd->timers[id];
> +	struct hrtimer *timer = &otgtimer->timer;
> +
> +	otgtimer->timeout = ms_to_ktime(expires_ms);
> +	hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
> +	timer->function = callback;
> +
> +	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);

2 timers are missing: B_DATA_PLS, B_SSEND_SRP.

> +}
> +
> +/**
> + * 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 otg_timer *otgtimer = &otgd->timers[id];
> +	struct hrtimer *timer = &otgtimer->timer;
> +
> +	if (!otgd->fsm_running)
> +		return;
> +
> +	/* if timer is already active, exit */
> +	if (hrtimer_active(timer)) {
> +		dev_err(otgd->dev, "otg: timer %d is already running\n", id);
> +		return;
> +	}
> +
> +	hrtimer_start(timer, otgtimer->timeout, HRTIMER_MODE_REL);
> +}
> +
> +/**
> + * 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 hrtimer *timer = &otgd->timers[id].timer;
> +
> +	hrtimer_cancel(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);
> +	struct otg_hcd_ops *hcd_ops;
> +
> +	dev_dbg(otgd->dev, "otg: %s %d\n", __func__, on);
> +	if (!fsm->otg->host) {
> +		WARN_ONCE(1, "otg: fsm running without host\n");
> +		return 0;
> +	}
> +
> +	if (on) {
> +		/* OTG device operations */
> +		if (otgd->start_host)
> +			otgd->start_host(fsm, on);
> +
> +		/* start host */
> +		hcd_ops = otgd->primary_hcd.ops;
> +		hcd_ops->add(otgd->primary_hcd.hcd, otgd->primary_hcd.irqnum,
> +			     otgd->primary_hcd.irqflags);
> +		if (otgd->shared_hcd.hcd) {
> +			hcd_ops = otgd->shared_hcd.ops;
> +			hcd_ops->add(otgd->shared_hcd.hcd,
> +				     otgd->shared_hcd.irqnum,
> +				     otgd->shared_hcd.irqflags);
> +		}
> +	} else {
> +		/* stop host */
> +		if (otgd->shared_hcd.hcd) {
> +			hcd_ops = otgd->shared_hcd.ops;
> +			hcd_ops->remove(otgd->shared_hcd.hcd);
> +		}
> +		hcd_ops = otgd->primary_hcd.ops;
> +		hcd_ops->remove(otgd->primary_hcd.hcd);
> +
> +		/* OTG device operations */
> +		if (otgd->start_host)
> +			otgd->start_host(fsm, on);
> +	}
> +
> +	return 0;
> +}

I do not see much benefit by this override function, usb_add/remove_hcd
can be simply included by controller's start_host function, also there
maybe some additional operations after usb_add_hcd, but this override
function limit usb_add_hcd() is the last step.

Maybe your intention is to make usb_add_hcd is the only operation required
to start host, so ideally controller driver need not define its start_host
routine for this otg ops, I am not sure if this can work for different otg
platforms. If the shared code is only usb_add/remove_hcd(), maybe leave this
ops defined by controller driver can make core code simple and give flexibility
to controller drivers.

> +
> +/**
> + * 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);
> +	struct usb_gadget *gadget = fsm->otg->gadget;
> +
> +	dev_dbg(otgd->dev, "otg: %s %d\n", __func__, on);
> +	if (!gadget) {
> +		WARN_ONCE(1, "otg: fsm running without gadget\n");
> +		return 0;
> +	}
> +
> +	if (on) {
> +		/* OTG device operations */
> +		if (otgd->start_gadget)
> +			otgd->start_gadget(fsm, on);
> +
> +		otgd->gadget_ops->start(fsm->otg->gadget);
> +	} else {
> +		otgd->gadget_ops->stop(fsm->otg->gadget);
> +
> +		/* OTG device operations */
> +		if (otgd->start_gadget)
> +			otgd->start_gadget(fsm, on);
> +	}
> +
> +	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);
> +
> +	otg_statemachine(&otgd->fsm);

Need consider runtime pm, or you want to rely on controller driver take
care of it?

> +}
> +
> +/**
> + * 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, "otg: %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, "otg: %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, "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 (otgd->fsm.otg->host || otgd->fsm.otg->gadget) {
> +		dev_err(parent_dev, "otg: %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, "otg: can't start till host registers\n");
> +		return;
> +	}
> +

This cannot work, fsm->otg->host is set in usb_otg_register_hcd(), which is
called by usb_add_hcd(), but usb_add_hcd() should be called only if otg fsm
already started to some A-device state, deadlock.

> +	if (!fsm->otg->gadget) {
> +		dev_info(otgd->dev, "otg: can't start 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++)
> +		hrtimer_cancel(&otgd->timers[i].timer);
> +
> +	flush_workqueue(otgd->wq);
> +	fsm->otg->state = OTG_STATE_UNDEFINED;
> +
> +	/* 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);
> +	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 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, "otg: %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
> + * @irqnum:	interrupt number
> + * @irqflags:	interrupt flags
> + * @ops:	HCD ops to add/remove 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.
> + *
> + * 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 otg_data *otgd;
> +	struct device *otg_dev = hcd->self.controller->parent;
> +
> +	mutex_lock(&otg_list_mutex);
> +	otgd = usb_otg_device_get_otgd(otg_dev);
> +	if (!otgd) {
> +		dev_dbg(otg_dev, "otg: %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->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 == otgd->primary_hcd.hcd) {
> +			if (otgd->shared_hcd.hcd) {
> +				dev_err(otg_dev, "otg: shared host already registered\n");
> +				goto err;
> +			}
> +
> +			otgd->shared_hcd.hcd = hcd;
> +			otgd->shared_hcd.irqnum = irqnum;
> +			otgd->shared_hcd.irqflags = irqflags;
> +			otgd->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;
> +		}
> +
> +		otgd->primary_hcd.hcd = hcd;
> +		otgd->primary_hcd.irqnum = irqnum;
> +		otgd->primary_hcd.irqflags = irqflags;
> +		otgd->primary_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 (otgd->shared_hcd.hcd || !otgd->primary_hcd.hcd->shared_hcd) {
> +		otgd->fsm.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(&otgd->fsm);

usb_otg_register_hcd() is called before usb_otg_add_hcd(), start fsm on
this point can make sense since hcd has not been added?

> +	} else {
> +		dev_dbg(otg_dev, "otg: can't start till shared host registers\n");
> +	}
> +
> +	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, "otg: %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 (hcd == otgd->primary_hcd.hcd) {
> +		otgd->primary_hcd.hcd = NULL;
> +		dev_info(otg_dev, "otg: primary host %s unregistered\n",
> +			 dev_name(bus->controller));
> +	} else if (hcd == otgd->shared_hcd.hcd) {
> +		otgd->shared_hcd.hcd = NULL;
> +		dev_info(otg_dev, "otg: shared host %s unregistered\n",
> +			 dev_name(bus->controller));
> +	} else {
> +		dev_err(otg_dev, "otg: host %s wasn't registered with otg\n",
> +			dev_name(bus->controller));
> +		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);
> +
> +	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.
> + *
> + * 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 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, "otg: %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, "otg: gadget already registered with otg\n");
> +		mutex_unlock(&otgd->fsm.lock);
> +		return -EINVAL;
> +	}
> +
> +	otgd->fsm.otg->gadget = gadget;
> +	otgd->gadget_ops = ops;
> +	dev_info(otg_dev, "otg: gadget %s registered\n",
> +		 dev_name(&gadget->dev));
> +
> +	/* start 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, "otg: %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, "otg: gadget %s wasn't registered with otg\n",
> +			dev_name(&gadget->dev));
> +		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, "otg: gadget %s unregistered\n",
> +		 dev_name(&gadget->dev));
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_unregister_gadget);
> +
> +/**
> + * usb_otg_fsm_to_dev - Get OTG controller device from struct otg_fsm
> + * @fsm:	otg_fsm data structure
> + *
> + * This is used by the OTG controller driver to get it's device node
> + * from any of the otg_fsm->ops.
> + */
> +struct device *usb_otg_fsm_to_dev(struct otg_fsm *fsm)
> +{
> +	struct otg_data *otgd = container_of(fsm, struct otg_data, fsm);
> +
> +	return otgd->dev;
> +}
> +EXPORT_SYMBOL_GPL(usb_otg_fsm_to_dev);
> 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@ti.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)
> +

All otg timer timeout value should be in some *range* defined by otg spec,
not some specific value, I don't think one specific value can meet all otg
platforms, so we need find a way to make those value can be configured by
controller drivers.

> +#endif /* __DRIVERS_USB_COMMON_USB_OTG_H */
> diff --git a/drivers/usb/core/Kconfig b/drivers/usb/core/Kconfig
> index a99c89e..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
> @@ -75,15 +75,6 @@ config USB_OTG_BLACKLIST_HUB
>  	  and software costs by not supporting external hubs.  So
>  	  are "Embedded Hosts" that don't offer OTG support.
>  
> -config USB_OTG_FSM
> -	tristate "USB 2.0 OTG FSM implementation"
> -	depends on USB
> -	select USB_OTG
> -	select USB_PHY
> -	help
> -	  Implements OTG Finite State Machine as specified in On-The-Go
> -	  and Embedded Host Supplement to the USB Revision 2.0 Specification.
> -
>  config USB_ULPI_BUS
>  	tristate "USB ULPI PHY interface support"
>  	depends on USB_SUPPORT
> diff --git a/include/linux/usb/otg.h b/include/linux/usb/otg.h
> index 52661c5..ce6f8d8 100644
> --- a/include/linux/usb/otg.h
> +++ b/include/linux/usb/otg.h
> @@ -10,6 +10,11 @@
>  #define __LINUX_USB_OTG_H
>  
>  #include <linux/phy/phy.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>
>  #include <linux/usb/phy.h>
>  
>  struct usb_otg {
> @@ -23,6 +28,7 @@ struct usb_otg {
>  
>  	enum usb_otg_state	state;
>  
> +/*------------- deprecated interface -----------------------------*/
>  	/* bind/unbind the host controller */
>  	int	(*set_host)(struct usb_otg *otg, struct usb_bus *host);
>  
> @@ -38,11 +44,85 @@ struct usb_otg {
>  
>  	/* start or continue HNP role switch */
>  	int	(*start_hnp)(struct usb_otg *otg);
> -
> +/*---------------------------------------------------------------*/
>  };
>  
>  extern const char *usb_otg_state_string(enum usb_otg_state state);
>  
> +enum usb_dr_mode {
> +	USB_DR_MODE_UNKNOWN,
> +	USB_DR_MODE_HOST,
> +	USB_DR_MODE_PERIPHERAL,
> +	USB_DR_MODE_OTG,
> +};
> +
> +#if IS_ENABLED(CONFIG_USB_OTG)
> +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, 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 otg_fsm *fsm);
> +int usb_otg_kick_fsm(struct device *hcd_gcd_device);
> +struct device *usb_otg_fsm_to_dev(struct otg_fsm *fsm);
> +
> +#else /* CONFIG_USB_OTG */
> +
> +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, unsigned int irqnum,
> +				       unsigned long irqflags,
> +				       struct otg_hcd_ops *ops)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int usb_otg_unregister_hcd(struct usb_hcd *hcd)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline int usb_otg_register_gadget(struct usb_gadget *gadget,
> +					  struct otg_gadget_ops *ops)
> +{
> +	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)
> +{
> +}
> +
> +static inline int usb_otg_kick_fsm(struct device *hcd_gcd_device)
> +{
> +	return -ENOSYS;
> +}
> +
> +static inline struct device *usb_otg_fsm_to_dev(struct otg_fsm *fsm)
> +{
> +	return NULL;
> +}
> +
> +#endif /* CONFIG_USB_OTG */
> +
> +/*------------- deprecated interface -----------------------------*/
>  /* Context: can sleep */
>  static inline int
>  otg_start_hnp(struct usb_otg *otg)
> @@ -94,14 +174,9 @@ 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);
>  
> -enum usb_dr_mode {
> -	USB_DR_MODE_UNKNOWN,
> -	USB_DR_MODE_HOST,
> -	USB_DR_MODE_PERIPHERAL,
> -	USB_DR_MODE_OTG,
> -};
> -
>  #endif /* __LINUX_USB_OTG_H */
> -- 
> 2.1.4
> 

I assume I will have more comments after try more.

Li Jun 
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