Stratix 10, Load FPGA image in u-boot


I’m using Stratix 10 board. Currently, I try to load FPGA image(.rbf) from SD Card during u-boot, however it always shows unknown error. Basically, my steps are very simple below:

a) power up the board and enter u-boot
b) run “fatload mmc 0: 1 0x8000 test.rbf”
c) run “fpga load 0 0x8000 $filesize”

And then an “Unknown error” appears.

Could someone give me a hint about this issue?

Thanks a lot.