How to use Secure Monitor Call(SMC) and entrance Monitor Mode?

Hello, experts:

My platform has a Cortex-A9 MPCore cpu, It supports trustzone tech.

I want to change NSACR.TL bit, but It need in secure state.

I want to change non-secure state to secure state by entering monitor mode using smc.

But It is not easy to understand how to use smc by reading ARM reference manual.

So, is there any sample code? or would you give some suggestions about this problem?

Best wishes,