Re: [PATCH v6 15/28] ARM: tegra: Add usb-role-switch property to USB OTG ports

[Dmitry Osipenko]

15.12.2021 18:52, Thierry Reding пишет:
>>> On the other hand, at least Venice2 has a USB type A connector for this,
>>> so I'm not even sure how that would work. I vaguely recall that the
>>> Tegra20 Seaboard also had a USB type A and that it was possible to use
>>> it in device mode, but I don't how that would. Nor would it be correct
>>> to use the gpio-usb-b-connector compatible for that since, well, it's
>>> not USB type B.
>> I'm not sure whether it makes much sense to use OTG for USB type A
>> connectors, normally they should be fixed to host mode.
> My recollection is that those can be used in device mode as well. For
> example that USB type A port on Venice2 (same as for Seaboard) can be
> used for RCM, IIRC. It's possible that there's no way to detect what is
> connected, though, so this may not be proper OTG.

Sounds correct.

>>> I suspect that Apalis has a micro-B port, much like the Jetson TK1. My
>>> understanding is that OTG doesn't work on Jetson TK1 (which is why it's
>>> configured in "host" mode), so it'd be interesting to see if this can be
>>> made to work on Apalis.
>> Looks like the default Apalis carrier board has three type A connectors.
>>
>> https://www.toradex.com/products/carrier-board/ixora-carrier-board
> I'm wondering if the best thing would be to mark all of these as "host"
> for now and avoid making this look like something that it isn't. I don't
> think we've ever made OTG work on these boards, so perhaps we shouldn't
> assume that it works.

Marking them "host" should be correct, but that wasn't tested.

I assume that those "OTG" ports may default to the host mode.