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

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Date:   Thu, 3 Nov 2022 09:04:53 +0100
From:   Francesco Dolcini <francesco@...cini.it>
To:     Alexander Stein <alexander.stein@...tq-group.com>
Cc:     Philippe Schenker <philippe.schenker@...adex.com>,
        Shawn Guo <shawnguo@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Fabio Estevam <festevam@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        NXP Linux Team <linux-imx@....com>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        linux-kernel@...r.kernel.org, Philippe Schenker <dev@...henker.ch>
Subject: Re: [PATCH] ARM: dts: colibri-imx6ull: Enable dual-role switching

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 ...

Francesco