Le mardi 08 novembre 2016 à 10:54 +0200, Peter De Schrijver a écrit : > On Mon, Nov 07, 2016 at 02:09:31PM +0000, Jon Hunter wrote: > > > > 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. > > 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/
Attachment:
signature.asc
Description: This is a digitally signed message part