[coreboot] Debug MRC.BIN, how to make ramstage CBMEM persistant across reboot ?

Hi,

I'm trying to debug the MRC.BIN on a T440p (more details here : https://www.reddit.com/r/coreboot/comments/ft4950/t440p_32gb_of_ram/)

However I cannot access the debug logs of the previous boot when I use CBMEM, it seems it's wiped out on the next boot.

Do you know how could I access the ramstage CBMEM logs to see exactly where  the MRC.BIN fails ?
There is no serial port on the T440p, and the USB 2.0 debug port is not exposed, so it seems that using CBMEM is the only option.

Thank you,
Baylee4