[MPC8272ADS]Cannot start my Linux Kernel

[Jean-Michel Hautbois]

I am now trying to use an initial RAM filesystem.
I have this:

"checking if image is initramfs... it is"
And then, after some hardware detections:
"List of all partitions:
1f00            8192 mtdblock0 (driver?)
No filesystem could mount root, tried:  ext3 ext2 cramfs
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(1,0)
Rebooting in 180 seconds..."

When using a NFS root file system, it is ok.
I have passed these args to my kernel:

bootargs root=/dev/ram ro init=/linuxrc noapic acpi=off nofb

I tried also root=/dev/ram0 but it is not working better.
My kernel .config contains:
CONFIG_BLK_DEV_INITRD=y
CONFIG_BLK_DEV_RAM=y
CONFIG_BLK_DEV_RAM_COUNT=16
CONFIG_BLK_DEV_RAM_SIZE=8192

Do I need to have MTD_RAM = y ?
Is there any other thing I should set to Y for it to work ?

Thx & Regards,
JM