Le mardi 08 novembre 2016 ? 10:54 +0200, Peter De Schrijver a ?crit?:

On Mon, Nov 07, 2016 at 02:09:31PM +0000, Jon Hunter wrote:

quoted

On 07/11/16 13:28, Thierry Reding wrote:

quoted

* PGP Signed by an unknown key

On Sun, Sep 18, 2016 at 12:28:52PM +0200, Paul Kocialkowski wrote:

quoted

Nyan boards only have host USB ports (2 external, 1 internal), there is
no OTG-enabled connector.

Signed-off-by: Paul Kocialkowski <redacted>
---
?arch/arm/boot/dts/tegra124-nyan.dtsi | 2 +-
?1 file changed, 1 insertion(+), 1 deletion(-)

Where is this information coming from? I don't have one of the Nyans
myself, but one of the Tegra132 devices I have, which I think was
derived from one of the Nyans uses one of the external host ports as
forced recovery port, for which it would need OTG.

I suspect that the way to get U-Boot onto the Nyans is via tegrarcm?
In that case I think one of the ports must be OTG.

It is true that the port on the back on the nyan-big can be used with
recovery mode. I was thinking that this is not a true OTG port as it is
just a 4-pin type A socket and does not have an ID pin. Thinking some
more about this the USB spec does include a "Host Negotiation Protocol
(HNP)" that allows a host and device to swap roles and so keeping it as
OTG seems valid afterall.

I don't think the bootrom implements that though. I expect recovery mode
to just program the controller in device mode, without performing any
negotiation.

That would make sense.

However, if there's a way (even not implemented yet, but a possible way) to have
the kernel configure this port as USB device instead of host dynamically (e.g.
without changing this bit in the dts), then I think it makes sense to keep the
OTG marking and drop this patch.

After all, switching to USB device mode doesn't necessarily have to come from
the ID pin.

-- 
Paul Kocialkowski, developer of free digital technology at the lower levels

Website: https://www.paulk.fr/
Coding blog: https://code.paulk.fr/
Git repositories: https://git.paulk.fr/ https://git.code.paulk.fr/
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