不能获取flash信息，不能烧写uboot到ram，请指教
sudo sunxi-fel ver
AWUSBFEX soc=00001681(V3s) 00000001 ver=0001 44 08 scratchpad=00007e00 00000000 00000000
sudo ./sunxi-fel -l
USB device 002:006 Allwinner V3s 12c00003:94004620:78a74220:040e0650
sudo sunxi-fel spiflash-info
usb_bulk_send() ERROR -7: Operation timed out
sunxi-fel uboot /home/hao/u-boot/u-boot-sunxi-with-spl.bin
usb_bulk_send() ERROR -7: Operation timed out
