[U-Boot] About assign parameters for bootm command

Hi,

I'd like to assign some kernel parameters via bootm cmd, but its failed. For example, I'de like to pass the below parameters for the kernel: root=/dev/mtdblock0 ro rootfstype=jffs2

Could someone show me how I can pass them into kernel? Thanks in advance! The flash on my board couldn't be overwrotten currently, so I have to boot os from RAM...

All the best, Mike