On Tue, Apr 09, 2019 at 12:58:51AM +0200, Ondřej Jirman wrote:
> > > +&usb2otg {
> > > + dr_mode = "host";
> > > + status = "okay";
> > > +};
> > > +
> > > +&usb2phy {
> > > + usb0_id_det-gpios = <&pio 2 15 GPIO_ACTIVE_HIGH>; /* PC15 */
> > > + usb0_vbus-supply = <®_vcc5v>;
> > > + usb3_vbus-supply = <®_vcc5v>;
> > > + status = "okay";
> >
> > If we have an ID pin, then why is the OTG controller set to host?
>
> This board has fixed conenction between VBUS and DCIN, so if it is powered
> from DCIN and someone will try to connect it to the PC as a peripheral,
> they'll get PC's VBUS shorted to the power supply connected to DCIN.
>
> Depending on voltage difference between DCIN and PC's VBUS, you can get
> overcurrent condidion and PC's port shutdown.
>
> The board is not entirely foolproof in this regard.
>
> - It can be host powered when connected via microUSB
> - It can be self-powered and host an device on microUSB
> - It can be self-powered and serve as a peripheral if you modify
> a cable (cut VBUS) or the host is expecting this and has some
> VBUS detection logic (most hosts will not have this)
>
> I just didn't want to encourage use as a peripheral, because it's not
> very foolproof. But I guess, DTS file will not stop anyone anyway.
>
> I'll change it to otg, and maybe leave a small note.
Your solution was great actually. I guess making a comment explaining
what you just did would be better though, so that no one is confused.
Maxime
--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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