linux-kernel - Re: [PATCH 1/3] dt-bindings: usb: ci-hdrc-usb2: add property disable-runtime-pm

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Message-ID: <6dc0449f57405c997ce94ef9e9ea6435fb6c0a7d.camel@toradex.com>
Date:   Mon, 13 Jul 2020 08:20:09 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "festevam@...il.com" <festevam@...il.com>
CC:     "Peter.Chen@....com" <Peter.Chen@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "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>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] dt-bindings: usb: ci-hdrc-usb2: add property
 disable-runtime-pm

On Fri, 2020-07-10 at 12:56 -0300, Fabio Estevam wrote:
> Hi Philippe,
> 
> On Fri, Jul 10, 2020 at 12:51 PM Philippe Schenker
> <philippe.schenker@...adex.com> wrote:
> > Chipidea depends on some hardware signals to be there in order
> 
> I think this description is too vague.
> 
> Could you please provide more details so that a user can know if their
> hardware falls into this category?
> 
> It is not clear from seeing this series what is the hardware details
> that would require this property to be used.

Hi Fabio, Peter,

I tried to keep the description for this patch somewhat general. But as
Peter suggested I will add Toradex's use-case for this.

The problem with Colibri iMX6ULL is that we are stuck with a legacy
module standard that does only include one USB host/device switching
signal. Plus on that specific module we have no 5V available hence left
the connection of VBUS signal away.
This works normally pretty well but for our "dual-role OTG" port I could
not make it work with runtime-pm running and proper extcon
configuration. The problem was, when plugging in something in device or
host mode gets not enumerated and detected.

That are the reasons why I believe the PHY or something else in Chipidea
needs a signal that it does not have on that module that would wake the
whole thing from runtime-suspend.

I will think about a better description and send a v2

Thanks
Philippe