linux-kernel - Re: [PATCH v8 13/14] usb: gadget: udc: adapt to OTG core

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Date:	Mon, 16 May 2016 12:51:53 +0300
From:	Roger Quadros <rogerq@...com>
To:	Peter Chen <hzpeterchen@...il.com>
CC:	<peter.chen@...escale.com>, <balbi@...nel.org>, <tony@...mide.com>,
	<gregkh@...uxfoundation.org>, <dan.j.williams@...el.com>,
	<mathias.nyman@...ux.intel.com>, <Joao.Pinto@...opsys.com>,
	<sergei.shtylyov@...entembedded.com>, <jun.li@...escale.com>,
	<grygorii.strashko@...com>, <yoshihiro.shimoda.uh@...esas.com>,
	<robh@...nel.org>, <nsekhar@...com>, <b-liu@...com>,
	<linux-usb@...r.kernel.org>, <linux-omap@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <devicetree@...r.kernel.org>
Subject: Re: [PATCH v8 13/14] usb: gadget: udc: adapt to OTG core

On 16/05/16 12:23, Peter Chen wrote:
> On Mon, May 16, 2016 at 11:26:57AM +0300, Roger Quadros wrote:
>> Hi,
>>
>> On 16/05/16 10:02, Peter Chen wrote:
>>> On Fri, May 13, 2016 at 01:03:27PM +0300, Roger Quadros wrote:
>>>> +
>>>> +static int usb_gadget_connect_control(struct usb_gadget *gadget, bool connect)
>>>> +{
>>>> +	struct usb_udc *udc;
>>>> +
>>>> +	mutex_lock(&udc_lock);
>>>> +	udc = usb_gadget_to_udc(gadget);
>>>> +	if (!udc) {
>>>> +		dev_err(gadget->dev.parent, "%s: gadget not registered.\n",
>>>> +			__func__);
>>>> +		mutex_unlock(&udc_lock);
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
>>>> +	if (connect) {
>>>> +		if (!gadget->connected)
>>>> +			usb_gadget_connect(udc->gadget);
>>>> +	} else {
>>>> +		if (gadget->connected) {
>>>> +			usb_gadget_disconnect(udc->gadget);
>>>> +			udc->driver->disconnect(udc->gadget);
>>>> +		}
>>>> +	}
>>>> +
>>>> +	mutex_unlock(&udc_lock);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>
>>> Since this is called for vbus interrupt, why not using
>>> usb_udc_vbus_handler directly, and call udc->driver->disconnect
>>> at usb_gadget_stop.
>>
>> We can't assume that this is always called for vbus interrupt so
>> I decided not to call usb_udc_vbus_handler.
>>
>> udc->vbus is really pointless for us. We keep vbus states in our
>> state machine and leave udc->vbus as ture always.
>>
>> Why do you want to move udc->driver->disconnect() to stop?
>> If USB controller disconnected from bus then the gadget driver
>> must be notified about the disconnect immediately. The controller
>> may or may not be stopped by the core.
>>
> 
> Then, would you give some comments when this API will be used?
> I was assumed it is only used for drd state machine.

drd_state machine didn't even need this API in the first place :).
You guys wanted me to separate out start/stop and connect/disconnect for full OTG case.
Won't full OTG state machine want to use this API? If not what would it use?

cheers,
-roger

> 
>>>
>>>>  	return 0;
>>>> @@ -660,9 +830,15 @@ static ssize_t usb_udc_softconn_store(struct device *dev,
>>>>  		return -EOPNOTSUPP;
>>>>  	}
>>>>  
>>>> +	/* In OTG mode we don't support softconnect, but b_bus_req */
>>>> +	if (udc->gadget->otg_dev) {
>>>> +		dev_err(dev, "soft-connect not supported in OTG mode\n");
>>>> +		return -EOPNOTSUPP;
>>>> +	}
>>>> +
>>>
>>> The soft-connect can be supported at dual-role mode currently, we can
>>> use b_bus_req entry once it is implemented later.
>>
>> Soft-connect should be done via sysfs handling within the OTG core.
>> This can be added later. I don't want anything outside the OTG core
>> to handle soft-connect behaviour as it will be hard to keep things
>> in sync.
>>
>> I can update the comment to something like this.
>>
>> /* In OTG/dual-role mode, soft-connect should be handled by OTG core */
> 
> Ok, let's Felipe decide it.
> 
>>
>>>
>>>>  	if (sysfs_streq(buf, "connect")) {
>>>>  		usb_gadget_udc_start(udc);
>>>> -		usb_gadget_connect(udc->gadget);
>>>> +		usb_udc_connect_control(udc);
>>>
>>> This line seems to be not related with this patch.
>>>
>> Right. I'll remove it.
>>
>> cheers,
>> -roger
>