Problem with Oprofile on Beagleboard

Hi all,

I am using oprofile on my Beagleboard-xm, and what I am going to do is
using oprofile to characterize performance of some application running
on android.

In order to do some analyze , I want to take some different
metrics(ex: L1_INST , L2_ACCESS , ...) rather than just default
CPU_CYCLES metric.

But i cannot get any sample from oprofile after I change the setting
of the metric.

i.e., I can get sample if I use
ex: opcontrol --setup --event=CPU_CYCLES:100000

but cannot get any sample if I use metrics that need to programmed on
Performance Monitoring Unit (PMU).
ex: opcontrol --setup -event=L1_INST

Does anyone encounter same problem ??

Thanks!