Physical counter in juno board

Hi Mark,

I tried reading the values in DS-5.

Reading CNTPCT_EL0 register in EL2 (Hypervisor mode) in AArch64 state results in this value. Also, I observed a similar behaviour when I read the memory mapped CNTCV value (0x2a800000).

Secondary core reports a lower value than the primary core as time goes by.

Thanks,

Gowthami

Hi Mark,

I tried reading the values in DS-5.

Reading CNTPCT_EL0 register in EL2 (Hypervisor mode) in AArch64 state results in this value. Also, I observed a similar behaviour when I read the memory mapped CNTCV value (0x2a800000).

Secondary core reports a lower value than the primary core as time goes by.

Thanks,

Gowthami

Hi,

That's confusing, it's not what I see on my board.

Although you haven't said what the magnitude of the difference is that's concerning you.

A couple of thoughts:

• Although the System Timer count is based on a common timebase, the architecture allows for some flexibility (latency when reading via different observers/mechanisms) as long as time can't be seen to go backwards. So I wouldn't necessarily expect to see the same count in such a test, just similar counts.
• Note the debugger will read the register once on entry to debug state and effectively show a "cached" value. You need to manually refresh the view it to get an updated reading.