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

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Date:	Mon, 16 May 2016 11:26:57 +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

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.

> 
>>  	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 */

> 
>>  	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