linux-kernel - Re: [PATCH v6 09/12] usb: gadget: udc: adapt to OTG core

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Message-ID: <5720A106.1030702@ti.com>
Date:	Wed, 27 Apr 2016 14:22:46 +0300
From:	Roger Quadros <rogerq@...com>
To:	Jun Li <jun.li@....com>,
	"stern@...land.harvard.edu" <stern@...land.harvard.edu>,
	"balbi@...nel.org" <balbi@...nel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"peter.chen@...escale.com" <peter.chen@...escale.com>
CC:	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"jun.li@...escale.com" <jun.li@...escale.com>,
	"mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	"tony@...mide.com" <tony@...mide.com>,
	"Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
	"abrestic@...omium.org" <abrestic@...omium.org>,
	"r.baldyga@...sung.com" <r.baldyga@...sung.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>
Subject: Re: [PATCH v6 09/12] usb: gadget: udc: adapt to OTG core

On 26/04/16 03:07, Jun Li wrote:
> Hi
> 
>> -----Original Message-----
>> From: Roger Quadros [mailto:rogerq@...com]
>> Sent: Monday, April 25, 2016 10:04 PM
>> To: Jun Li <jun.li@....com>; stern@...land.harvard.edu; balbi@...nel.org;
>> gregkh@...uxfoundation.org; peter.chen@...escale.com
>> Cc: dan.j.williams@...el.com; jun.li@...escale.com;
>> mathias.nyman@...ux.intel.com; tony@...mide.com; Joao.Pinto@...opsys.com;
>> abrestic@...omium.org; r.baldyga@...sung.com; linux-usb@...r.kernel.org;
>> linux-kernel@...r.kernel.org; linux-omap@...r.kernel.org
>> Subject: Re: [PATCH v6 09/12] usb: gadget: udc: adapt to OTG core
>>
>> Hi,
>>
>> On 21/04/16 09:38, Jun Li wrote:
>>> Hi,
>>>
>>> ...
>>>>
>>>>  /**
>>>> + * usb_gadget_start - start the usb gadget controller and connect to
>>>> +bus
>>>> + * @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).
>>>> + */
>>>> +static 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_gadget_udc_start(udc);
>>>> +	if (ret)
>>>> +		dev_err(&udc->dev, "USB Device Controller didn't start: %d\n",
>>>> +			ret);
>>>> +	else
>>>> +		usb_udc_connect_control(udc);
>>>
>>> For drd, it's fine, but for real otg, gadget connect should be done by
>>> loc_conn() instead of gadget start.
>>
>> It is upto the OTG state machine to call gadget_start() when it needs to
>> connect to the bus (i.e. loc_conn()). I see no point in calling gadget
>> start before.
>>
>> Do you see any issue in doing so?
> 
> This is what OTG state machine does:
> case OTG_STATE_B_PERIPHERAL:
>      otg_chrg_vbus(otg, 0);
>      otg_loc_sof(otg, 0);
>      otg_set_protocol(fsm, PROTO_GADGET);
>      otg_loc_conn(otg, 1);
>      break;
> 
> You intend to abstract something common in this api when start gadget,
> which should be called by otg_set_protocol(fsm, PROTO_GADGET); and
> drd_set_protocol(fsm, PROTO_GADGET); right?
> 
> So you may move usb_udc_connect_control(IMO usb_gadget_connect()
> is better)out of usb_gadget_start(), then for drd:
> 
> case OTG_STATE_B_PERIPHERAL:
>      drd_set_protocol(fsm, PROTO_GADGET);
>      otg_drv_vbus(otg, 0);
>      usb_gadget_connect();

OK. I understand now. I'll implement your suggestion. Thanks.

cheers,
-roger

>>>
>>>> +
>>>> +	mutex_unlock(&udc_lock);
>>>> +
>>>> +	return ret;
>>>> +}
>>>> +
>>>> +/**
>>>> + * usb_gadget_stop - disconnect from bus and 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.
>>>> + */
>>>> +static int usb_gadget_stop(struct usb_gadget *gadget) {
>>>> +	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:
>>>> +	usb_gadget_disconnect(udc->gadget);
>>>
>>> Likewise, gadget disconnect also should be done by loc_conn() instead
>>> of gadget stop.
>>>
>>>> +	udc->driver->disconnect(udc->gadget);
>>>> +	usb_gadget_udc_stop(udc);
>>>> +	mutex_unlock(&udc_lock);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>
>>> Li Jun
>>>