linux-kernel - Re: [PATCH v2 2/2] Revert "usb: dwc3: Don't switch OTG -> peripheral if extcon is present"

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Message-ID: <20221006020014.66tl3ba22dkdsavp@synopsys.com>
Date:   Thu, 6 Oct 2022 02:00:29 +0000
From:   Thinh Nguyen <Thinh.Nguyen@...opsys.com>
To:     Andrey Smirnov <andrew.smirnov@...il.com>
CC:     Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
        Ferry Toth <fntoth@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Felipe Balbi <balbi@...nel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v2 2/2] Revert "usb: dwc3: Don't switch OTG -> peripheral
 if extcon is present"

On Tue, Oct 04, 2022, Andrey Smirnov wrote:
> On Tue, Oct 4, 2022 at 7:12 PM Thinh Nguyen <Thinh.Nguyen@...opsys.com> wrote:
> >
> > On Tue, Oct 04, 2022, Ferry Toth wrote:
> > > Hi
> > >
> > > Op 04-10-2022 om 10:28 schreef Andy Shevchenko:
> > > > On Mon, Oct 03, 2022 at 09:57:35PM +0000, Thinh Nguyen wrote:
> > > > > On Tue, Sep 27, 2022, Andy Shevchenko wrote:
> > > > > > This reverts commit 0f01017191384e3962fa31520a9fd9846c3d352f.
> > > > > >
> > > > > > As pointed out by Ferry this breaks Dual Role support on
> > > > > > Intel Merrifield platforms.
> > > > > Can you provide more info than this (any debug info/description)? It
> > > > > will be difficult to come back to fix with just this to go on. The
> > > > > reverted patch was needed to fix a different issue.
> > >
> > > On Merrifield we have a switch with extcon driver to switch between host and
> > > device mode. Now with commit 0f01017, device mode works. In host mode the
> > > root hub appears, but no devices appear. In the logs there are no messages
> > > from tusb1210, but there should be because lately there normally are
> > > (harmless) error messages. Nothing in the logs point in the direction of
> > > tusb1210 not being probed.
> > >
> > > The discussion is here: https://urldefense.com/v3/__https://lkml.org/lkml/2022/9/24/237__;!!A4F2R9G_pg!avfDjiGwi8xu0grHYrQQTZEEUnmaKu82xxdty0ZltxyU8BkoFD6AMq4a-7STYiKxNQpdYXgP1QG_IZbroEM$
> > >
> > > I tried moving some code as suggested without result: https://urldefense.com/v3/__https://lkml.org/lkml/2022/9/24/434__;!!A4F2R9G_pg!avfDjiGwi8xu0grHYrQQTZEEUnmaKu82xxdty0ZltxyU8BkoFD6AMq4a-7STYiKxNQpdYXgP1QG_boaK8Qw$
> > >
> > > And with success: https://urldefense.com/v3/__https://lkml.org/lkml/2022/9/25/285__;!!A4F2R9G_pg!avfDjiGwi8xu0grHYrQQTZEEUnmaKu82xxdty0ZltxyU8BkoFD6AMq4a-7STYiKxNQpdYXgP1QG_MbbbZII$
> > >
> > > So, as Andrey Smirnov writes "I think we'd want to figure out why the
> > > ordering is important if we want to justify the above fix."
> > >
> > > > It's already applied, but Ferry probably can provide more info if you describe
> > > > step-by-step instructions. (I'm still unable to test this particular type of
> > > > features since remove access is always in host mode.)
> > > >
> > > I'd be happy to test.
> >
> > Thanks!
> >
> > Does the failure only happen the first time host is initialized? Or can
> > it recover after switching to device then back to host mode?
> >
> > Probably the failure happens if some step(s) in dwc3_core_init() hasn't
> > completed.
> >
> > tusb1210 is a phy driver right? The issue is probably because we didn't
> > initialize the phy yet. So, I suspect placing dwc3_get_extcon() after
> > initializing the phy will probably solve the dependency problem.
> >
> > You can try something for yourself or I can provide something to test
> > later if you don't mind (maybe next week if it's ok).
> 
> FWIW, I just got the same HW Ferry has last week and am planning to
> work on this over the weekend.

That'd be great. Thanks!

Thinh