thank. In the samples folder I found a file named `example_kernel_emmc.uuu`, I will try that first.
In the `example_kernel_emmc.uuu`, a file like `initramfs.cpio.gz.uboot` is needed, I didn't find a document about how to generate that file, so I'm planning to use the 'fsl-image-mfgtool-initramfs-imx_mfgtools.cpio.gz.u-boot' in the demo image folder. Should it be OK?