Hi Stephen,

-----Original Message-----
From: linux-usb-owner at vger.kernel.org [mailto:linux-usb-
owner at vger.kernel.org] On Behalf Of Peter Chen
Sent: Thursday, June 30, 2016 9:27 AM
To: Stephen Boyd <redacted>
Cc: linux-usb at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
linux-kernel at vger.kernel.org; linux-arm-msm at vger.kernel.org; Andy Gross
[off-list ref]; Bjorn Andersson [off-list ref];
Neil Armstrong [off-list ref]; Arnd Bergmann [off-list ref];
Felipe Balbi [off-list ref]; Peter Chen [off-list ref]; Greg
Kroah-Hartman [off-list ref]
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:

quoted

Quoting Peter Chen (2016-06-28 20:09:13)

quoted

On Sun, Jun 26, 2016 at 12:28:25AM -0700, Stephen Boyd wrote:

quoted

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.

quoted

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.

quoted

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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