Re: [PATCH v1 0/3] usb: dwc3: Avoid using reserved EPs

Andy Shevchenko
2025-01-17T13:38:51Z

On Thu, Jan 16, 2025 at 11:18:45PM +0000, Thinh Nguyen wrote:
> On Thu, Jan 16, 2025, Andy Shevchenko wrote:
> > On some platforms (Intel-based and AFAIK ARM-based) the EPs in the gadget
> > (USB Device Controller mode) may be reserved for some special means, such as
> > tracing. This series extends DT schema and driver to avoid using those.
> > Without this the USB gadget mode won't work properly (those devices that
> > "luckily" allocated the reserved EPs).
> >
> > Ferry already tested the privately sent PoC of this, but I ask him again to
> > re-test this version which is slightly different.

...

> I'm not entirely clear on the reason for this change yet.
>
> How would this even work without dwc3 managing these endpoints (all the
> init/teardown/fifo allocation/start/stop flow).

You perhaps know much better how it can be done, I have access to a limited
documentation and in practice if those endpoints are not skipped any gadget
that allocates them simply won't work, and IIRC the entire USB transfers are
stuck.

> Can you provide more info on this hardware?

I am afraid I can't provide more, sorry. I can look for some specifics,
but I'm not that guy who know anything about in-SoC tracing.

--
With Best Regards,
Andy Shevchenko