usb otg help needed

[mongoose]

ls /sys/class/udc > UDC
ls:write error: Device or resource busy

I'm trying to get an armbian device (banana pi m2 zero and/or the orange pi zero LTS) to function as a USB client, but I can't seem to get the above step working. Any suggestions? lsof UDC returns nothing.

 

On the RaspberryPI 4 this worked without issue 

Edited September 13, 2022 by mongoose

[goosnarrggh]

The driver for USB OTG gadgets in most (all?) Allwinner chips is limited to PIO (polled I/O). That would have a couple of important implications including very high CPU utilization and limited data throughput. It's might be possible to improve the driver to give it DMA support, which could improve performance and reduce CPU usage. But it looks like nobody's working on it right now.

 

https://linux-sunxi.org/Linux_mainlining_effort#Drivers_that_can_still_be_improved.2Fadded

 

That being said, it should at least be possible even if it may be sub-optimal. Maybe you're missing a device tree overlay? Or maybe the relevant USB gadget kernel modules aren't compiled/installed? I'm hoping to spin up a new orange pi zero in the next little while; hopefully I can remember to take a look.

[mongoose]

@goosnarrggh (Late) thanks for the reply! Did you happen to get a chance to play with this?