[U-Boot] A command to discard saved environments?

Hi.

I am looking for a command that discards the saved environments, and takes me back to the "*** Warning - bad CRC, using default environment" state.

In my case, the environment data is saved at sector 0x400 of the MMC device on my board.

So, I can just do

mmc erase 400 10

But, beforehand, I need to know

CONFIG_ENV_IS_IN_MMC CONFIG_ENV_OFFSET 0x80000

in order to confirm if the above command is doing the right thing. (If I make a mistake in calculating the offset value, other data would be damaged.)

Is there a nice command to do that?