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Date:	Thu, 19 Mar 2015 11:30:01 +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 2/9] usb: gadget: add usb_gadget_start/stop()

On Wed, Mar 18, 2015 at 03:55:56PM +0200, Roger Quadros wrote:
> The OTG state machine needs a mechanism to start and
> stop the gadget controller. Add usb_gadget_start()
> and usb_gadget_stop().
> 
> Signed-off-by: Roger Quadros <rogerq@...com>
> ---
>  drivers/usb/gadget/udc/udc-core.c | 166 +++++++++++++++++++++++++++++++++++---
>  include/linux/usb/gadget.h        |   3 +
>  2 files changed, 158 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/usb/gadget/udc/udc-core.c b/drivers/usb/gadget/udc/udc-core.c
> index 5a81cb0..69b4123 100644
> --- a/drivers/usb/gadget/udc/udc-core.c
> +++ b/drivers/usb/gadget/udc/udc-core.c
> @@ -35,6 +35,8 @@
>   * @dev - the child device to the actual controller
>   * @gadget - the gadget. For use by the class code
>   * @list - for use by the udc class driver
> + * @running - udc is running

Doesn't OTG FSM should know it?

Peter
> + * @softconnect - sysfs softconnect says OK to connect
>   *
>   * This represents the internal data structure which is used by the UDC-class
>   * to hold information about udc driver and gadget together.
> @@ -44,6 +46,8 @@ struct usb_udc {
>  	struct usb_gadget		*gadget;
>  	struct device			dev;
>  	struct list_head		list;
> +	bool				running;
> +	bool				softconnect;
>  };
>  
>  static struct class *udc_class;
> @@ -187,7 +191,14 @@ EXPORT_SYMBOL_GPL(usb_gadget_udc_reset);
>   */
>  static inline int usb_gadget_udc_start(struct usb_udc *udc)
>  {
> -	return udc->gadget->ops->udc_start(udc->gadget, udc->driver);
> +	int ret;
> +
> +	dev_dbg(&udc->dev, "%s\n", __func__);
> +	ret = udc->gadget->ops->udc_start(udc->gadget, udc->driver);
> +	if (!ret)
> +		udc->running = 1;
> +
> +	return ret;
>  }
>  
>  /**
> @@ -204,10 +215,140 @@ static inline int usb_gadget_udc_start(struct usb_udc *udc)
>   */
>  static inline void usb_gadget_udc_stop(struct usb_udc *udc)
>  {
> +	dev_dbg(&udc->dev, "%s\n", __func__);
>  	udc->gadget->ops->udc_stop(udc->gadget);
> +	udc->running = 0;
>  }
>  
>  /**
> + * usb_udc_start - Start the usb device controller only if conditions met
> + * @udc: The UDC to be started
> + *
> + * Start the UDC and connect to bus (enable pull) only if the
> + * following conditions are met
> + * - UDC is not already running
> + * - gadget function driver is loaded
> + * - userspace softconnect says OK to connect
> + *
> + * NOTE: udc_lock must be held by caller.
> + *
> + * Returs 0 on success or not ready to start, else negative errno.
> + */
> +static int usb_udc_start(struct usb_udc *udc)
> +{
> +	int ret;
> +
> +	if (udc->running) {
> +		dev_err(&udc->dev, "%s: not starting as already running\n",
> +			__func__);
> +		return -EBUSY;
> +	}
> +
> +	if (udc->driver && udc->softconnect) {
> +		ret = usb_gadget_udc_start(udc);
> +		if (ret)
> +			return ret;
> +
> +		usb_gadget_connect(udc->gadget);
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * usb_udc_stop - Stop the usb device controller
> + * @udc: The UDC to be stopped
> + *
> + * Disconnect from bus (disable pull) and stop the UDC.
> + *
> + * NOTE: udc_lock must be held by caller.
> + *
> + * Returs 0 on success, else negative errno.
> + */
> +static int usb_udc_stop(struct usb_udc *udc)
> +{
> +	if (!udc->running) {
> +		dev_err(&udc->dev, "%s: not stopping as already halted\n",
> +			__func__);
> +		return -EBUSY;
> +	}
> +
> +	usb_gadget_disconnect(udc->gadget);
> +	udc->driver->disconnect(udc->gadget);
> +	usb_gadget_udc_stop(udc);
> +
> +	return 0;
> +}
> +
> +/**
> + * usb_gadget_start - start the usb gadget controller
> + * @gadget: the gadget device to start
> + *
> + * This is external API for use by OTG core.
> + *
> + * Start the usb device controller and connect to bus (enable pull).
> + * There is no guarantee that the controller is started
> + * as we might be missing some dependencies
> + * i.e. gadget function driver not loaded or softconnect disabled.
> + */
> +int usb_gadget_start(struct usb_gadget *gadget)
> +{
> +	int ret;
> +	struct usb_udc *udc = NULL;
> +
> +	dev_dbg(&gadget->dev, "%s\n", __func__);
> +	mutex_lock(&udc_lock);
> +	list_for_each_entry(udc, &udc_list, list)
> +		if (udc->gadget == gadget)
> +			goto found;
> +
> +	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
> +		__func__);
> +	mutex_unlock(&udc_lock);
> +	return -EINVAL;
> +
> +found:
> +	ret = usb_udc_start(udc);
> +	mutex_unlock(&udc_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(usb_gadget_start);
> +
> +/**
> + * usb_gadget_stop - stop the usb gadget
> + * @gadget: The gadget device we want to stop
> + *
> + * This is external API for use by OTG core.
> + *
> + * Disconnect from the bus (disable pull) and stop the
> + * gadget controller.
> + */
> +int usb_gadget_stop(struct usb_gadget *gadget)
> +{
> +	int ret;
> +	struct usb_udc *udc = NULL;
> +
> +	dev_dbg(&gadget->dev, "%s\n", __func__);
> +	mutex_lock(&udc_lock);
> +	list_for_each_entry(udc, &udc_list, list)
> +		if (udc->gadget == gadget)
> +			goto found;
> +
> +	dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
> +		__func__);
> +	mutex_unlock(&udc_lock);
> +	return -EINVAL;
> +
> +found:
> +	ret = usb_udc_stop(udc);
> +	mutex_unlock(&udc_lock);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(usb_gadget_stop);
> +
> +/**
>   * usb_udc_release - release the usb_udc struct
>   * @dev: the dev member within usb_udc
>   *
> @@ -278,6 +419,7 @@ int usb_add_gadget_udc_release(struct device *parent, struct usb_gadget *gadget,
>  		goto err3;
>  
>  	udc->gadget = gadget;
> +	udc->softconnect = 1;	/* connect by default */
>  
>  	mutex_lock(&udc_lock);
>  	list_add_tail(&udc->list, &udc_list);
> @@ -329,10 +471,8 @@ static void usb_gadget_remove_driver(struct usb_udc *udc)
>  
>  	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
>  
> -	usb_gadget_disconnect(udc->gadget);
> -	udc->driver->disconnect(udc->gadget);
> +	usb_udc_stop(udc);
>  	udc->driver->unbind(udc->gadget);
> -	usb_gadget_udc_stop(udc);
>  
>  	udc->driver = NULL;
>  	udc->dev.driver = NULL;
> @@ -378,6 +518,7 @@ EXPORT_SYMBOL_GPL(usb_del_gadget_udc);
>  
>  /* ------------------------------------------------------------------------- */
>  
> +/* udc_lock must be held */
>  static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *driver)
>  {
>  	int ret;
> @@ -392,12 +533,12 @@ static int udc_bind_to_driver(struct usb_udc *udc, struct usb_gadget_driver *dri
>  	ret = driver->bind(udc->gadget, driver);
>  	if (ret)
>  		goto err1;
> -	ret = usb_gadget_udc_start(udc);
> +
> +	ret = usb_udc_start(udc);
>  	if (ret) {
>  		driver->unbind(udc->gadget);
>  		goto err1;
>  	}
> -	usb_gadget_connect(udc->gadget);
>  
>  	kobject_uevent(&udc->dev.kobj, KOBJ_CHANGE);
>  	return 0;
> @@ -510,12 +651,15 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
>  	}
>  
>  	if (sysfs_streq(buf, "connect")) {
> -		usb_gadget_udc_start(udc);
> -		usb_gadget_connect(udc->gadget);
> +		mutex_lock(&udc_lock);
> +		udc->softconnect = 1;
> +		usb_udc_start(udc);
> +		mutex_unlock(&udc_lock);
>  	} else if (sysfs_streq(buf, "disconnect")) {
> -		usb_gadget_disconnect(udc->gadget);
> -		udc->driver->disconnect(udc->gadget);
> -		usb_gadget_udc_stop(udc);
> +		mutex_lock(&udc_lock);
> +		udc->softconnect = 0;
> +		usb_udc_stop(udc);
> +		mutex_unlock(&udc_lock);
>  	} else {
>  		dev_err(dev, "unsupported command '%s'\n", buf);
>  		return -EINVAL;
> diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
> index e2f00fd..7ada7e6 100644
> --- a/include/linux/usb/gadget.h
> +++ b/include/linux/usb/gadget.h
> @@ -922,6 +922,9 @@ int usb_gadget_probe_driver(struct usb_gadget_driver *driver);
>   */
>  int usb_gadget_unregister_driver(struct usb_gadget_driver *driver);
>  
> +int usb_gadget_start(struct usb_gadget *gadget);
> +int usb_gadget_stop(struct usb_gadget *gadget);
> +
>  extern int usb_add_gadget_udc_release(struct device *parent,
>  		struct usb_gadget *gadget, void (*release)(struct device *dev));
>  extern int usb_add_gadget_udc(struct device *parent, struct usb_gadget *gadget);
> -- 
> 2.1.0
> 

-- 

Best Regards,
Peter Chen
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