I downgraded to power-kernel v46, then there's a uboot-power package which works perfectly with power-kernel v46(not v47 which is in the newest in the repos).

First I followed these instructions:
http://wiki.maemo.org/Kernel_Power#Deinstallation
But I didn't reboot at the end.

Then I ran the command in this post:
http://talk.maemo.org/showpost.php?p...09&postcount=6

After that, you can simply "apt-get install uboot-power" and once you reboot, you'll see uboot. However, all future kernel-power upgrades will be held back until uboot-power is upgraded to support v47.

Also, do this at your own risk, it's not my fault if your N900 fails to boot.