Invalid FAT entry (uboot)

Did you encounter

Invalid FAT entry

when using fatload or fatls command in uboot?
possibly the filesystem is corrupted (from the view of uboot).
For instance,

U-Boot > fatls mmc 0
2187544 uimage
Invalid FAT entry

1 file(s), 0 dir(s)

Try to format the partition to fat. (mkfs.vfat)
Copy origin files into it and try again.