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

[Jun Li]

Hi Stephen,

> -----Original Message-----
> From: linux-usb-owner@xxxxxxxxxxxxxxx [mailto:linux-usb-
> owner@xxxxxxxxxxxxxxx] On Behalf Of Peter Chen
> Sent: Thursday, June 30, 2016 9:27 AM
> To: Stephen Boyd <stephen.boyd@xxxxxxxxxx>
> Cc: linux-usb@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; Andy Gross
> <andy.gross@xxxxxxxxxx>; Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>;
> Neil Armstrong <narmstrong@xxxxxxxxxxxx>; Arnd Bergmann <arnd@xxxxxxxx>;
> Felipe Balbi <balbi@xxxxxxxxxx>; Peter Chen <peter.chen@xxxxxxx>; Greg
> Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 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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