U-BOOT ARM: How to copy in U-boot the MMC1 (SD) to MMC0 (eMMC) ?

Hello,

U-boot:

mmc info

mmc0 is eMMC with fast write/read. the default one.
mmc dev 0 0
mmc dev 0 1
mmc dev 0 2


mmc1 is the SD card, inserted.
mmc dev 1 0
mmc dev 1 1
mmc dev 1 2

printenv
shows
boot_targets mmc0 mmc1 usb0

So how to copy within u-boot the mmc1 to mmc0 ?
i.e. How to copy in U-boot the MMC1 (SD) to MMC0 (eMMC) ?

Thank you!

Kind regards