From: Peter Chen <peter.chen@nxp.com>
To: Stefan Agner <stefan@agner.ch>, Peter Chen <hzpeterchen@gmail.com>
CC: Sanchayan Maity <maitysanchayan@gmail.com>,
        "linux-usb@vger.kernel.org" <linux-usb@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "ivan.ivanov@linaro.org" <ivan.ivanov@linaro.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "shawnguo@kernel.org" <shawnguo@kernel.org>,
        "marcel@ziswiler.com" <marcel@ziswiler.com>
Subject: RE: [RFC PATCH 0/4] Implement USB device/host switch for Vybrid
Thread-Topic: [RFC PATCH 0/4] Implement USB device/host switch for Vybrid
Thread-Index: AQHRfpbZAapanA/FP0SKak35j46ZtJ9p1iGAgAU5joCAAJV5QA==
Date: Tue, 29 Mar 2016 00:24:46 +0000
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References: <cover.1458030082.git.maitysanchayan@gmail.com>
 <20160325074051.GB22398@peterchendt>
 <3c2e72efc8cae93ff31be1b44f9a02b3@agner.ch>
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> 
> On 2016-03-25 00:40, Peter Chen wrote:
> > On Tue, Mar 15, 2016 at 02:08:26PM +0530, Sanchayan Maity wrote:
> >> Hello Peter,
> >>
> >> The existing usage of extcon in Chipidea driver relies on OTG
> >> registers. In case of SoC with dual role device but not a true OTG
> >> controller, this does not work. Such SoC's should specify the
> >> existing CI_HDRC_DUAL_ROLE_NOT_OTG flag and do the role switch
> >> without checking any of the OTG registers in my opinion.
> >> This is the case for Vybrid which uses a Chipidea IP but does not
> >> have a true 5 pin OTG implemented.
> >
> > Sorry to reply you late due to my new born baby.
> >
> > Are you sure Vybrid is NOT OTG core? Afaik, it is uses the same IP
> > base with other Freescale SoCs, just the IP core is 2.40a.
> > When working at device mode, can you read vbus status through OTGSC?
> > And if there is an ID pin (input pin) for Vybrid? I mean SoC, not the
> > board.
> 
> I think the IP is actually OTG capable, the registers are there, but the signals
> seem not to be available on the SoC package. That is also what the RM says...
> 
> Quotes from the RM:
> 
> "OTG controller should be treated as
> Dual role controller that allows the
> controller to act as either a Host or a
> device with no support for HNP/SRP."
> 
> And later, in Chapter 11.1:
> 
> "The USB is not a true OTG. It can be configured by software to function either
> as peripheral or as host. The ID pin, which is unique for OTG operation, is not
> present in this implementation. There are no five pin interface. The user will
> get four pin host/ device interface."
> 

Get it, thanks. I am doing a patch for covering this case and vbus always-on case.

Peter