linux-kernel - Re: [PATCH] ARM: dts: colibri-imx6ull: Enable dual-role switching

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Message-ID: <f901af9b264ee58233c3549f85ee876829fdd721.camel@toradex.com>
Date:   Mon, 7 Nov 2022 12:00:18 +0000
From:   Philippe Schenker <philippe.schenker@...adex.com>
To:     "francesco@...cini.it" <francesco@...cini.it>,
        "alexander.stein@...tq-group.com" <alexander.stein@...tq-group.com>
CC:     "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "linux-imx@....com" <linux-imx@....com>,
        "festevam@...il.com" <festevam@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "krzysztof.kozlowski+dt@...aro.org" 
        <krzysztof.kozlowski+dt@...aro.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>
Subject: Re: [PATCH] ARM: dts: colibri-imx6ull: Enable dual-role switching

On Thu, 2022-11-03 at 09:04 +0100, Francesco Dolcini wrote:
> On Thu, Nov 03, 2022 at 08:46:58AM +0100, Alexander Stein wrote:
> > Hi Philippe,
> > 
> > Am Mittwoch, 2. November 2022, 16:52:26 CET schrieb Philippe
> > Schenker:
> > > From: Philippe Schenker <philippe.schenker@...adex.com>
> > > 
> > > The Colibri standard provides a GPIO called USBC_DET to switch
> > > from
> > > USB Host to USB Device and back. The Colibri iMX6ULL does have the
> > > SoC
> > > ball USB_OTG1_VBUS connected in series with a capacitor to ground.
> > > 
> > > This means that we need to provide to the extcon framework VBUS
> > > and ID
> > > events using the single GPIO we have. The Extcon USB GPIO driver
> > > does
> > > use id-gpio also for VBUS event, as in our case where vbus-gpio is
> > > absent.
> > > 
> > > Signed-off-by: Philippe Schenker <philippe.schenker@...adex.com>
> > > 
> > > ---
> > > 
> > >  arch/arm/boot/dts/imx6ull-colibri.dtsi | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > > 
> > > diff --git a/arch/arm/boot/dts/imx6ull-colibri.dtsi
> > > b/arch/arm/boot/dts/imx6ull-colibri.dtsi index
> > > 577a424b0e1d..feb1fcd9a684
> > > 100644
> > > --- a/arch/arm/boot/dts/imx6ull-colibri.dtsi
> > > +++ b/arch/arm/boot/dts/imx6ull-colibri.dtsi
> > > @@ -24,6 +24,13 @@ backlight: backlight {
> > >                 status = "okay";
> > >         };
> > > 
> > > +       extcon_usbc_det: usbc-det {
> > > +               compatible = "linux,extcon-usb-gpio";
> > > +               id-gpio = <&gpio5 2 GPIO_ACTIVE_HIGH>; /* SODIMM
> > > 137 / 
> > USBC_DET */
> > > +               pinctrl-names = "default";
> > > +               pinctrl-0 = <&pinctrl_snvs_usbc_det>;
> > > +       };
> > > +
> > >         gpio-keys {
> > >                 compatible = "gpio-keys";
> > >                 pinctrl-names = "default";
> > > @@ -275,6 +282,7 @@ &uart5 {
> > >  /* Colibri USBC */
> > >  &usbotg1 {
> > >         dr_mode = "otg";
> > > +       extcon = <&extcon_usbc_det>, <&extcon_usbc_det>;
> > 
> > How came you up with this double entries? Is there some
> > documentation you need 
> > two phandles?
> 
> extcon-usb-gpio provides both vbus/otg_id with a single handle,
> however
> the integration in chipidea is somehow weird, the first entry is
> supposed to be
> used to read the vbus, the second one to read the otg_id.
> 
> So if you need to read both you really need to have the handle twice
> ...

Thanks for the suggestion Alex and Francesco for answering. I cannot add
much more, we tried a lot back and forth due to the really special
hardware-design this solution was the best we found for the colibri-
imx6ull.

Regards,
Philippe

> 
> Francesco
>