[U-Boot] JFFS2 for a new User

[Alejandro Ariel Fachini]

Hello:

I've downloaded and compiled U-boot with buildroot for AT91sam9x35ek using
NANDFlash, and managed to get into console (after kernel load) with an
*.ubi RFS; but Im working in a project that has a RFS in jffs2 format(old
project started at 2011, RFS produced by Tool only in that format with
custom libraries i can't touch), basically i must use jffs2.
I am trying to make kernel linux4sam_5.6 boot into the same RFS but jffs2
format(also compiled by buildroot), this RFS is for testing, an empty
skeleton.
I tried changing bootargs several times copying from different websites but
I'm failing.
Can you please help me hoy can i modify these BOOTARGS for them to work
with *.jffs2 NandFlash for AT91sam9x35.
Before you ask, i have read U-boot manuals commands, how mtdparts works, i
cant find how to address my root="" boot arg clear enough to understand it.
I'll paste the ubi bootargs so you can explain me how to change them for
jffs2.

#define CONFIG_BOOTARGS                            \
    "console=ttyS0,115200 earlyprintk "                \
    "mtdparts=atmel_nand:256k(bootstrap)ro,512k(uboot)ro,"        \
    "256k(env),256k(env_redundant),256k(spare),"            \
    "512k(dtb),6M(kernel)ro,-(rootfs) "                \
    "rootfstype=ubifs ubi.mtd=7 root=ubi0:rootfs rw"
#endif