linux-kernel - RE: [PATCH v2 2/3] usb: chipidea: imx: support disabling runtime-pm

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Message-ID: <AM7PR04MB715721D95968DDB78B45A3AF8B7B0@AM7PR04MB7157.eurprd04.prod.outlook.com>
Date:   Mon, 20 Jul 2020 08:06:21 +0000
From:   Peter Chen <peter.chen@....com>
To:     Philippe Schenker <philippe.schenker@...adex.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
CC:     Jun Li <jun.li@....com>, dl-linux-imx <linux-imx@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "festevam@...il.com" <festevam@...il.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: RE: [PATCH v2 2/3] usb: chipidea: imx: support disabling runtime-pm

 
> On Mon, 2020-07-20 at 03:44 +0000, Peter Chen wrote:
> >
> > > On Wed, 2020-07-15 at 00:51 +0000, Peter Chen wrote:
> > > > > The Toradex Colibri iMX6ULL board has a special USB hardware
> > > > > design.
> > > > > With runtime-pm enabled USB reset itself continuously.
> > > > > Furthermore
> > > > > the OTG port is also not enumerating devices if the Chipidea IP
> > > > > is in runtime sleep mode and a device or host gets plugged in.
> > > > >
> > > >
> > > > Hi Philippe,
> > > >
> > > > You may describe the detail what's the special USB hardware design
> > > > for your board,
> > >
> > > If I only knew the root-cause of that problem - unfortunately I
> > > don't.
> > > That's also why I have such a hard time to describe it.
> > >
> > > > and why it causes the problem, and why disable runtime pm could
> > > > fix this issue, then,
> > >
> > > I cannot provide the 'why' part yet. I'll try something more and
> > > hope I can provide you guys with the exact description.
> > >
> > > > the other users could know if it could apply to their platforms or
> > > > not in future.
> > >
> > > I only found out about it because you were pointing me in that
> > > direction. I debugged for hours now and didn't came to the
> > > root-cause of the issue. I think to really understand it I would
> > > need to know much more about the Chipidea IP.
> > >
> > > I'll get back to you guys with a proposal for a new description.
> > >
> >
> > Philippe, is it possible to share your USB hardware design at 6ULL?
> 
> It's actually pretty simple: We have on USB_OTG1_VBUS a 1uF capacitor and
> +3.0V on VDD_USB_CAP together with 100n and 10u bypass caps. Now the big
> problem is that the driver can not detect the 5V on VBUS signal.
> 

Could you confirm it does not see VBUS at register OTGSC? If it is, how can it work with runtime
disabled, the USBCMD.RS setting (ci_hdrc_gadget_connect is called) depends on VBUS.

Peter

> I tried to 'inject' 5V to that pin last week and things got really better with runtime-pm.
> But I still thinks disabling it for our board would make sense.
> 
> I'll send a new description today where I try to point to VBUS signal not connected.
> 
> Philippe
> 
> > And how ci_hdrc_gadget_connect is called when the runtime pm is
> > disabled?
> >
> > Thanks,
> > Peter
> >