On Mon, Jun 24, 2024 at 2:39 PM Tim Harvey <thar...@gateworks.com> wrote: > > Greetings, > > What is missing in U-Boot for the DWC3 host controller to support OTG > mode for usb_ether (USB Ethernet gadget)? I'm unable to get the usb > ethernet gadget to work for the imx8mp as it errors out with 'No UDC > available in the system'. > > The ums/acm/sdp gadget's all call udc_device_get_by_index to get the > UDC controller which for DWC3 is provided by > drivers/usb/dwc3/dwc3-generic.c and these gadgets work, however > usb_ether is different in that it calls usb_gadget_register_driver to > bind the gadget driver to the UDC and for DWC3 this calls > usb_gadget_probe_driver which iterates over udc_list which does not > contain DWC3 hosts that are in peripheral/otg mode. > > Before I spend a lot more time on this I wanted to see if anyone else > understands why boards with DWC3 host controllers like imx8mp don't > seem to register controllers in udc_list that are not in host mode. > > I'm also unclear how to get a DWC3 controller to switch roles > dynamically at runtime based on a gpio state for example. That support > appears to be missing and I'm not sure what the right way would be to > go about adding it. I notice that some imx8mp boards like the > imx8mp-evk have a u-boot.dtsi that just forces its OTG controller to > peripheral mode and I force the imx8mp-venice OTG controllers into > host mode.
I think there is some interaction between the DWC controller and a type-c controller, but I think the mainline code lacks a proper type-c controller and/or framework. Not everyone might use a USB Type-C chip, but it seems like if the USB is set to dual-role, it could default to peripheral mode until someone starts the USB host stuff with 'usb start' I am just not sure how to handle situations where a USB cable may be connected to a host computer and someone issues a start command and brings up VBUS which may cause a voltage contention. I think some people tried to push a Type-C driver if memory serves, but I think it was rejected. I don't recall the details and my memory is terrible. :-) adam > > Best Regards, > > Tim
