linux-kernel - RE: [PATCH 08/21] usb: chipidea: Kick OTG state machine for AVVIS with vbus extcon

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Date:	Thu, 30 Jun 2016 01:50:03 +0000
From:	Jun Li <jun.li@....com>
To:	Peter Chen <hzpeterchen@...il.com>,
	Stephen Boyd <stephen.boyd@...aro.org>
CC:	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
	Andy Gross <andy.gross@...aro.org>,
	"Bjorn Andersson" <bjorn.andersson@...aro.org>,
	Neil Armstrong <narmstrong@...libre.com>,
	Arnd Bergmann <arnd@...db.de>, Felipe Balbi <balbi@...nel.org>,
	Peter Chen <peter.chen@....com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: RE: [PATCH 08/21] usb: chipidea: Kick OTG state machine for AVVIS
 with vbus extcon

Hi Stephen,

> -----Original Message-----
> From: linux-usb-owner@...r.kernel.org [mailto:linux-usb-
> owner@...r.kernel.org] On Behalf Of Peter Chen
> Sent: Thursday, June 30, 2016 9:27 AM
> To: Stephen Boyd <stephen.boyd@...aro.org>
> Cc: linux-usb@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-kernel@...r.kernel.org; linux-arm-msm@...r.kernel.org; Andy Gross
> <andy.gross@...aro.org>; Bjorn Andersson <bjorn.andersson@...aro.org>;
> Neil Armstrong <narmstrong@...libre.com>; Arnd Bergmann <arnd@...db.de>;
> Felipe Balbi <balbi@...nel.org>; Peter Chen <peter.chen@....com>; Greg
> Kroah-Hartman <gregkh@...uxfoundation.org>
> Subject: Re: [PATCH 08/21] usb: chipidea: Kick OTG state machine for AVVIS
> with vbus extcon
> 
> On Wed, Jun 29, 2016 at 06:19:59PM -0700, Stephen Boyd wrote:
> > Quoting Peter Chen (2016-06-28 20:09:13)
> > > On Sun, Jun 26, 2016 at 12:28:25AM -0700, Stephen Boyd wrote:
> > > > Force the OTG state machine to go forward when we're using an
> > > > extcon for vbus detection. In this case, the controller may never
> > > > raise an interrupt for AVVIS, so we need to simulate the event by
> > > > toggling the appropriate OTG fsm bits and kicking the state
> > > > machine again.
> > > >
> > >
> > > Well, I think you may misunderstand the OTG FSM and dual-role.
> > > From my and Felipe's point, there are seldom users for USB FSM,
> > > there are only OTG FSM spec and related OTG certification.
> >
> > Probably yes.
> >
> > >
> > > The OTG FSM needs related SoC support, the vbus will be off at
> > > several states, and the SRP should be supported by SoC.
> > >
> > > By default, the dts needs below properties for disabling it if you
> > > choose otg fsm support at kernel configuration.
> > >
> > > &usbotg1 {
> > >         vbus-supply = <&reg_usb_otg1_vbus>;
> > >         srp-disable;
> > >         hnp-disable;
> > >         adp-disable;
> > >         status = "okay";
> > > };
> > >
> > > See Documentation/devicetree/bindings/usb/generic.txt.
> >
> > Does this mean we should be setting all those properties if we're
> > using an extcon for vbus and id?
> 
> It is not related to how we know vbus and id. If your controller is otg-
> capable, and you don't want to enable OTG FSM (just want dual-role), you
> should set them at dts since the zImage is multi-platforms, the
> CONFIG_USB_OTG and CONFIG_USB_OTG_FSM may be chosen.
> 
> > I have noticed that vbus is powered off after some time when no device
> > is connected and we're in A_HOST state because the timeout for a B
> > device connection happens.
> 
> I think it is not you want, but it is OTG compliance.

For simple, if you don't want OTG(i.e HNP&SRP) at all, just needs
dual role, you may disable CONFIG_USB_OTG and CONFIG_USB_OTG_FSM
in your menuconfig, then you don't need touch all those properties.

Li Jun

> 
> --
> 
> Best Regards,
> Peter Chen
> --
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