I will not say exactly when the USB port started working in 2.0 mode, but it seems that this problem appeared in version 19 of openWrt.
The built-in port works only at 1-1 Full-speed, no installed packages like "usb2", "usblibs" have any effect, any device works only at full-speed, be it a USB flash drive or card or portable hard drive.
usb 1-1: new full-speed USB device number 3 using xhci-mtk - any devices use this mode only. Sound Card:
USB Audio Device at usb-1e1c0000.xhci-1, full speed. The problem cannot be in the cord, it simply does not exist, flash drives and a sound card are plugged directly into the port of the router.
Of all the errors in the log, only
usb usb2: We don't know the algorithms for LPM for this host, disabling LPM.
How can I fix the problem and make USB work in 2.0 mode?