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

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Message-ID: <573C6347.6080705@ti.com>
Date:	Wed, 18 May 2016 15:42:47 +0300
From:	Roger Quadros <rogerq@...com>
To:	Jun Li <jun.li@....com>, Peter Chen <hzpeterchen@...il.com>
CC:	"peter.chen@...escale.com" <peter.chen@...escale.com>,
	"balbi@...nel.org" <balbi@...nel.org>,
	"tony@...mide.com" <tony@...mide.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"mathias.nyman@...ux.intel.com" <mathias.nyman@...ux.intel.com>,
	"Joao.Pinto@...opsys.com" <Joao.Pinto@...opsys.com>,
	"sergei.shtylyov@...entembedded.com" 
	<sergei.shtylyov@...entembedded.com>,
	"jun.li@...escale.com" <jun.li@...escale.com>,
	"grygorii.strashko@...com" <grygorii.strashko@...com>,
	"yoshihiro.shimoda.uh@...esas.com" <yoshihiro.shimoda.uh@...esas.com>,
	"robh@...nel.org" <robh@...nel.org>,
	"nsekhar@...com" <nsekhar@...com>, "b-liu@...com" <b-liu@...com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v8 13/14] usb: gadget: udc: adapt to OTG core

On 17/05/16 11:28, Jun Li wrote:
> Hi Roger,
> 
>> -----Original Message-----
>> From: Roger Quadros [mailto:rogerq@...com]
>> Sent: Tuesday, May 17, 2016 4:09 PM
>> To: Jun Li <jun.li@....com>; 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 17/05/16 10:38, Jun Li wrote:
>>> Hi
>>>
>>>> -----Original Message-----
>>>> From: Roger Quadros [mailto:rogerq@...com]
>>>> Sent: Monday, May 16, 2016 5:52 PM
>>>> 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?
>>>
>>> Instead create those new interfaces/symbol here and there just aim to
>>> address build problems in diff configures, Could we only allow
>>> meaningful combination of those 3 drivers configures?
>>>
>>> Hcd=y, gadget=y, otg=y or
>>> Hcd=m, gadget=m, otg=m
>>
>> This is still a limitation.
>>
>> It is perfectly fine to have
>> hcd=m, gadget=y
>> or
>> hcd=y, gadget=m
> 
> I agree it makes sense to have above configs in non-otg case, that is,
> the 'y' driver can work without 'm' driver loaded.
> 
> But,
> in otg enabled(y/m) case, the otherwise config of my list can't make
> any sense from my point view. That is: some driver is built-in, but
> it can't work at all if another 'm' driver is not loaded,
> 
> in another words, the otg driver has to be 'm' if its dependent driver
> is 'm', correct?

If both host and gadget are 'm' then otg can be 'm', but if either host or
gadget is built in then we have no choice but to make otg as built-in.

I didn't want to have complex Kconfig so decided to have otg as built-in only.
What do you want me to change in existing code? and why?

cheers,
-roger
    
> 
> Li Jun
> 
>>
>> cheers,
>> -roger
>>
>>>
>>> Li Jun
>>>
>>>>
>>>> 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
>>>>>