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SubjectRe: [PATCH v6 09/12] usb: gadget: udc: adapt to OTG core
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On 26/04/16 03:07, Jun Li wrote:
> Hi
>
>> -----Original Message-----
>> From: Roger Quadros [mailto:rogerq@ti.com]
>> Sent: Monday, April 25, 2016 10:04 PM
>> To: Jun Li <jun.li@nxp.com>; stern@rowland.harvard.edu; balbi@kernel.org;
>> gregkh@linuxfoundation.org; peter.chen@freescale.com
>> Cc: dan.j.williams@intel.com; jun.li@freescale.com;
>> mathias.nyman@linux.intel.com; tony@atomide.com; Joao.Pinto@synopsys.com;
>> abrestic@chromium.org; r.baldyga@samsung.com; linux-usb@vger.kernel.org;
>> linux-kernel@vger.kernel.org; linux-omap@vger.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
>>>

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