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

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Date:   Mon, 20 Jul 2020 07:51:29 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "peter.chen@....com" <peter.chen@....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@....com" <jun.li@....com>,
        "linux-imx@....com" <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.

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
>