Subject: Decoding the PTM traces

From: [email-masked] (Punit Agrawal)
Date: Wed, 14 Nov 2012 14:58:21 +0000

Hi Arun,

You can think of the trace in the ETB as the raw stream resulting from
the multiplexing of different trace streams. So to get to the PTM trace
you'll first have to de-multiplex the stream, and then decode the stream
based on the source - in this case PTM.

The format of the data stored in the ETB is described in the ETM TRM
Section 9.6
(http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0314h/Bgbhhidd.html).
The decoding should give you a trace stream for each active trace
source. The ATBID can be used to de-multiplex multiple sources, e.g.,
the two PTMs associated with the two A9s.

The PTM stream can then be decoded using the Program Flow Trace Protocol
described in Program Flow Trace Architecture Specification Section 4
(http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ihi0035b/Chddbbdf.html).

Out of curiosity, may I ask what are you trying to do?

Hope this helps. Feel free to ask for clarification.

Cheers,
Punit

On 14/11/12 14:04, Arun KS wrote:
> Hello,
>
> I m trying to capture and decode PTM trace from Cortex A9 dual core.
>
> I m successful  in configuring the driver(arch/arm/kernel/etm.c) and
> setting the funnel to get data in ETB.
> But I don't know how to decode these traces.
>
> Anyone has any pointers?
>
> Thanks,
> Arun
>
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