i.MX 8M Mini USB OTG

[xiaobao]

Want the USB OTG port on the IMX8 to connect only at low speed.  What's the best way to do that?

[igorpadykov]

Hi Xianbao

usb speed is detected automatically during enumeration (state of D+/D- lines), for details one can refer to

usb2.0 specification or simple description on

https://www.beyondlogic.org/usbnutshell/usb2.shtml

Best regards
igor

[xiaobao]

Hi Igor

I know usb speed is detected automatically during enumeration (state of D+/D- lines).

I see in the IMX8 datasheet(USBx_nPORTSC1 register bit of PFSC ) and the Chipidea /core.c:654 driver file that the configuration port is supported only at full speed connection.But,I don't see information in the IMX8 USB register instructions about configuring only low speed connections. 

Does USB OTG support driver configuration to connect only at low speeds?  

Best regards

xianbao

[igorpadykov]

>Does USB OTG support driver configuration to connect only at low speeds?

I am afraid not, sorry.

Best regards
igor

[xiaobao]

Thank you very much for your answer，Maybe I made a mistake.

On other platforms, USB speed can be limited by the “maximum-speed” attribute of the USB device tree node, but no configuration logic for USB speed is found in the IMX8USBOTG driver.  Can I limit the USB speed to low-speed through the driver?  If so, how to configure it?  

Best regards

xianbao