netconsole over USB net not working

[Andy Shevchenko]

Hi!

What is the Best Known Method to enable NetConsole over USB ethernet
gadget on DWC3?

Currently I have a "blinking" type of network interface (from the host
side) and it's too hard to understand all the mysterious ways of this
setup.

I have set std* to "nc,serial" (*) to be able to have the network
console be set up and running.

*) "serial" is just for the initial boot strap, this is a product
ready Android tablet that users are not supposed to solder wires on
its PCB. No need to say that I have another similar device
(https://lore.kernel.org/u-boot/CAHp75VdPTU-THtHi3eRiD7rd_tC90fC66AiUvzMnoF2Ky0J_HQ@mail.gmail.com/T/#u)
that has no serial interface at all, and I can't do anything about it
due to lack of support from U-Boot.

Unfortunately it goes this direction (in net_loop() call)
       net_init();
       if (eth_is_on_demand_init()) {
               eth_halt();
               eth_set_current();
               ret = eth_init();
               if (ret < 0) {
                       eth_halt();
                       return ret;
               }

The problem here is that the gadget timeouts for some reason and of
course for the default 3 seconds I may not have enough time to set up
the network on the host side. Moreover, if by luck I manage to achieve
that, it still doesn't work.

--- net_loop Entry
Trying usb_ether
0
  - 0 'dwc3'
  - found
using dwc3-gadget, OUT ep2out IN ep2in STATUS ep3in
MAC de:ad:be:ef:00:01
HOST MAC de:ad:be:ef:00:00
...
dwc3-generic-peripheral dwc3: Transfer Not Ready while ep0out in state
'Data Phase'dwc3-generic-peripheral dwc3:
Transfer Complete while ep0out in state 'Status Phase'The remote end
did not respond in time.eth_reset_config
dwc3-generic-peripheral dwc3: request 36561380 from ep3in completed
0/8 ===> -108
event 00 --> -108
eth_unbind...
FAIL

...and repeat...

Conclusion it is not working at all.

Expectations:
the USB gadget leaves UDC in state that the host would be able to set
up the link and the netconsole would be able to send data to it.

How to achieve that?

Alternative: serial function of the composite device. As of today not
an option — it simply does not exist in the U-Boot. Anybody is working
on that?

-- 
With Best Regards,
Andy Shevchenko