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

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Date:   Fri, 11 Nov 2022 13:17:21 +0800
From:   Shawn Guo <shawnguo@...nel.org>
To:     Francesco Dolcini <francesco@...cini.it>
Cc:     Alexander Stein <alexander.stein@...tq-group.com>,
        Philippe Schenker <philippe.schenker@...adex.com>,
        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 09:04:53AM +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 input, Francesco!

Philippe,

Do you consider to use usb-role-switch as suggested by Alexander,
considering the weirdness of how chipidea driver supports extcon-usb-gpio?

Shawn