Recently I used
flex-builder -i mkrfs -r buildroot:tiny -a arm32 # generate arm32 little-endian rootfs as per qoriq_arm64_devel_defconfig
to generate a rootfs then after I use make ARCH=arm menuconfig to get every modules compiled
then I loaded into the linux but I found out that there is no /boot directory for me to configure the device tree file in order to make the usb3.0 works as serial gadget.
So once I loaded modprobe g_serial
it thrown me error [ 0.200027] dwc3 3100000.usb3: Failed to get clk 'ref': -2
Can anyone help?