Re: [PATCH] ARM: tegra: nyan: Mark all USB ports as host

From: Jon Hunter
Date: Mon Nov 07 2016 - 09:12:26 EST

On 07/11/16 13:28, Thierry Reding wrote:
> * PGP Signed by an unknown key
> On Sun, Sep 18, 2016 at 12:28:52PM +0200, Paul Kocialkowski wrote:
>> Nyan boards only have host USB ports (2 external, 1 internal), there is
>> no OTG-enabled connector.
>> Signed-off-by: Paul Kocialkowski <contact@xxxxxxxx>
>> ---
>> 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.