I first do a usb start and then:
Here is my bootcmd
setenv bootcmd ext4load usb 0:2 $kernel_addr_r $image_name; ext4load usb 0:2 $fdt_addr_r $fdt_name; setenv bootargs $console root=/dev/sda2 rw rootwait net.ifnames=0 usbcore.autosuspend=-1 biosdevname=0; booti $kernel_addr_r – $fdt_addr_r