RE: [beagleboard] instruction counting in the beagleboard


I got around to testing the Performance Monitoring Unit.

I am using BeagleBoard rev C3, with OMAP3 PMU Main ID 0x411FC083.

PMCNT seems to work for some functions: instruction, cycle count.
I have not tested more, and probably won’t need to in the near future. From my experience with other arm chips I was never able to set range restrictions for the functionalities set in the core via EVTSEL.

All I had to do is to start the counters:
* globally from PMNC (p15,0, ,c9,c12,0), bit 0,
* as well as the particular counters to use: CNTENS (p15, 0 , , c9, c12, 1)

In order to see counter value, I had to:
* select counter I want PMNXSEL (p15,0, ,c9,c12,5).
* program functional event on which to count in EVTSEL (p15,0,,c9,c13,1)
* read/write to it PMCNT0-3 (p15,0,,c9,c13,2)

I was not able to find if the counter overflow is routed to a OMAP3 MPU.
So it seems it can be used only in polling mode.

If you ever find the interrupt number, please give me a reply email.

Happy hacking,
Gabi Voiculescu

— On Mon, 10/19/09, Henry Cox wrote:

> From: Henry Cox
> Subject: RE: [beagleboard] instruction counting in the beagleboard
> To: “Gabi Voiculescu”
> Date: Monday, October 19, 2009, 8:15 PM
> Hi -
> Saw your post;
> If you get any answers, please either forward them along to me or
> summarize to the group.
> I had asked some very similar questions about a year back - but
> never got an answer.
> The upshot from my experiments is that it was fairly straightforward
> to enable user access to the counters and that the cycle counter
> worked as I expected.
> Unfortunately, I was unable to get the performance counters to
> work: they appeared to be permanently disabled (i.e., would not
> increment when the configured event occurred). I’m reasonably
> sure that this is due to the setting of a memory-mapped register…but
> I was never able to figure out where the register is mapped to,
> or how to change its value on the beagleboard…
> Henry


What would be the best mailing list/email support to ask about the PMU IRQ?

Anybody has any ideas?

Thank you,
Gabi Voiculescu