BBB usb boot fails on SPL tftp

I’m porting BBBlfs bootloader server to nodejs. Now, after receiving tftp request for SPL, I’m transferring SPL.
I built spl/uboot with config am335x_evm_usbspl_defconfig . After SPL transfer it fails to boot, here’s the serial output:

U-Boot SPL 2017.07-rc1-00163-g8cb3ce6 (Jun 11 2017 - 01:09:02)
SPL: failed to boot from all boot devices

ERROR ### Please RESET the board

Please help me to debug this problem.
Code for server: