linux-kernel - Re: [PATCH 3/3] ARM: dts: colibri-imx7: add usb dual-role switch capability

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Message-ID: <5616f6e189845de7c4acfd9eede540ef6e6e9eb0.camel@toradex.com>
Date:   Mon, 20 Jul 2020 07:37:48 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "shawnguo@...nel.org" <shawnguo@...nel.org>
CC:     "a.fatoum@...gutronix.de" <a.fatoum@...gutronix.de>,
        "linux-imx@....com" <linux-imx@....com>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Subject: Re: [PATCH 3/3] ARM: dts: colibri-imx7: add usb dual-role switch
 capability

On Mon, 2020-07-20 at 10:11 +0800, Shawn Guo wrote:
> On Tue, Jul 14, 2020 at 08:20:34AM +0000, Philippe Schenker wrote:
> > On Tue, 2020-07-14 at 09:55 +0200, Ahmad Fatoum wrote:
> > > Hello Philippe,
> > > 
> > > On 7/13/20 1:53 PM, Philippe Schenker wrote:
> > > > On Mon, 2020-07-13 at 11:46 +0200, Ahmad Fatoum wrote:
> > > > > Hello Philippe,
> > > > > 
> > > > > > +	extcon_usbc_det: usbc_det {
> > > > > > +		compatible = "linux,extcon-usb-gpio";
> > > > > 
> > > > > According to 4602f3bff266 ("usb: common: add USB GPIO based
> > > > > connection
> > > > > detection driver"):
> > > > > "the old way using extcon to support USB Dual-Role switch is
> > > > > now
> > > > > deprecated
> > > > >  when use Type-B connector."
> > > > > 
> > > > > Have you considered using a compatible = "gpio-usb-b-
> > > > > connector"
> > > > > child
> > > > > node instead?
> > > > > 
> > > > > Cheers,
> > > > > Ahmad
> > > > 
> > > > Thanks for the Hint Ahmad,
> > > > 
> > > > I already tried and just now tried again but it doesn't work on
> > > > our
> > > > hardware. Are you sure this works with chipidea driver?
> > > 
> > > I haven't, just wanted to point its existence out in case you
> > > didn't
> > > know.
> > > Seems we need to call of_platform_populate somewhere in the
> > > driver.
> > > Unsure what other changes are necessary.
> > 
> > Yep, thanks for that! It seems like that need to be really called as
> > I
> > can't get a probe of the new usb connector driver. I quickly grepped
> > through code and saw that tegra USB driver is calling
> > of_platform_populate and they also use that gpio-usb-b-connector.
> > 
> > > > Should this new usb-connector stuff work in general with every
> > > > old
> > > > driver?
> > > 
> > > If the driver support isn't there yet, I think use of extcon is
> > > fine
> > > as is.
> 
> Shouldn't we improve chipidea driver to get it work with gpio-usb-b-
> connector?

I know this would be nice but I don't know that code well enough to be
able to make this changes in a timely manner. And I rather like to have
support for USB dual-role support "the old way" now than never (we
actually tried this for along time on our Colibri boards).

I discovered a bug in that driver together with Peter Chen, which got
now solved by him and I would like to use the host/device switching on
colibri-imx6/7 boards now.
> 
> Shawn