Hi Cheng,
ltib is good for use "as is" without tweaking around.
The imx28 support on this toolchain is quite limited.
If you start tweaking around you might run into several problems.
The best support found so far is the 'yocto' project / build chain.
The 'ELDK' and the 'openembedded' distris are based on this project.
You will find imx28evk config on this distris to start with.
Don´t waste your time with ltib and imx28.
rgds.