Unlocking RAPL in BIOS for Energy limiting

I am trying to perform some energy limiting tests on the Dell PowerEdge T630 systems running ubuntu 16.04 (Linux 4.4). The Intel(R) Xeon(R) CPU E5-2637 v3 supports the RAPL counters for getting energy usage as well as setting energy caps through a bunch of MSR registers at package level, core level, and DRAM level.

Though i can read the energy usage reporting registers, i cannot set the energy limit registers for package level (MSR_PKG_POWER_LIMIT).

sudo rdmsr -X --bitfield 63:63 0x00000610 gives a value of 1, which means the RAPL is locked in the BIOS (as per intel manual).

I can set the core energy limit registers for PP0 ( MSR_PP0_POWER_LIMIT) but it has no effect on the energy usage at all.

I have tried a lot of ways to reset the register bit : power_gov, wrmsr, changing bios setting to OS-driven energy management (instead of DAPC/DBPM), but nothing works.

CAN SOME PLEASE TELL HOW TO RESET THE POWER LIMITING REGISTERS TO PERFORM MANUAL ENERGY LIMITING ???