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Date:	Sat, 21 May 2016 10:44:47 +0800
From:	Peter Chen <hzpeterchen@...il.com>
To:	Roger Quadros <rogerq@...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 Fri, May 20, 2016 at 10:26:03AM +0300, Roger Quadros wrote:
> Peter,
> 
> On 20/05/16 04:39, Peter Chen wrote:
> > On Wed, May 18, 2016 at 03:45:11PM +0300, Roger Quadros wrote:
> >> On 18/05/16 06:18, Peter Chen wrote:
> >>> On Mon, May 16, 2016 at 12:51:53PM +0300, Roger Quadros wrote:
> >>>> 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?
> >>>>
> >>>
> >>> Oh, I meant only drd and fully otg state machine needs it. I am
> >>> wondering if we need have a new API to do it. Two questions:
> >>
> >> OK.
> >>>
> >>> - Except for vbus interrupt, any chances this API will be used at
> >>> current logic?
> >>
> >> I don't think so. But we can't assume caller behaviour for any API.
> >>
> >>> - When this API is called but without a coming gadget->stop?
> >>>
> >> Never for DRD case. But we want to catch wrong users.
> >>
> > 
> > In future, otg_start_gadget will be used for both DRD and fully OTG FSM.
> > There is no otg_loc_conn at current DRD FSM, but there is
> > otg_loc_conn at current OTG FSM, see below.
> > 
> > DRD FSM:
> > 	case OTG_STATE_B_IDLE:
> > 		drd_set_protocol(fsm, PROTO_UNDEF);
> > 		otg_drv_vbus(otg, 0);
> > 		break;
> > 	case OTG_STATE_B_PERIPHERAL:
> > 		drd_set_protocol(fsm, PROTO_GADGET);
> > 		otg_drv_vbus(otg, 0);
> > 		break;
> > 
> > OTG FSM:
> > 	case OTG_STATE_B_IDLE:
> > 		otg_drv_vbus(otg, 0);
> > 		otg_chrg_vbus(otg, 0);
> > 		otg_loc_conn(otg, 0);
> > 		otg_loc_sof(otg, 0);
> > 		/*
> > 		 * Driver is responsible for starting ADP probing
> > 		 * if ADP sensing times out.
> > 		 */
> > 		otg_start_adp_sns(otg);
> > 		otg_set_protocol(fsm, PROTO_UNDEF);
> > 		otg_add_timer(otg, B_SE0_SRP);
> > 		break;
> > 	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;
> > 
> > My original suggestion is to have an API to do pull dp and this API
> > will be used at both DRD and OTG FSM, and called at otg_loc_conn.
> 
> The API is usb_gadget_connect_control();
> 
> > The (de)initialize is the same for both two FSMs, it both includes
> > init peripheral mode and pull up dp, and can be done by drd_set_protocol(fsm, PROTO_GADGET)
> > otg_loc_conn(otg, 1);
> > 
> > What do you think?
> > 
> 
> I think loc_conn is a bit confusing to drd users. Another issue I see is that 
> DRD controller drivers will need to explicitly pass .loc_conn ops via the otg_fsm_ops.
> This is an additional step and totally unnecessary as it can be automatically done
> via direct DRD -> UDC-core call.
> 

If you are stick to that, let's follow your way if Felipe agree with it
too, although it lets the DRD state machine look different with OTG's.

-- 

Best Regards,
Peter Chen

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