Reading and Decoding Data From ETB Buffer

[Mathieu Poirier]

Adding the coresight mailing list

On Tue, 12 Jan 2021 at 04:17, Ajay Bharadwaj <ajayrbharadwaj at gmail.com> wrote:
>
> Hi,
>
> I'm working on enabling STM and ETB support on Texas Instruments' platforms.
>
> Currently, I can write directly to the STM device in sysfs and read back
> the encoded data from the ETB's buffer. I am using the Trace Packet
> Lister (trc_pkt_lister) from Linaro's OpenCSD [1] to decode the data
> obtained from the ETB. The decoded data matches what was written to the
> STM (Albeit the data is reversed in some cases, this seems to be
> expected according to the ARM specification).
>
> However, when I use the STM Source Console [2] instead of writing
> directly to the STM device, I can still read back the encoded data from
> the ETB buffer but OpenCSD cannot find any trace data in it.
>
> Is there any other tool that I can use instead of OpenCSD or am I doing
> something wrong? Here are the commands I am running (I've tried using
> the p_sys-t STP policy as well with the same result):
>
> Enabling CoreSight and STM Source Console:
> 1. mkdir -p /config
> 2. mount -t configfs none /config
> 3. mkdir /config/stp-policy/stm0.policy
> 4. mkdir /config/stp-policy/stm0.policy/console
> 5. echo 1 > /sys/bus/coresight/devices/etb0/enable_sink
> 6. echo stm0 > /sys/class/stm_source/console/stm_source_link
>
> Reading decoded data from ETB buffer:
> 1. dd if=/dev/etb0 of=test.bin
>
> OpenCSD Output:
> Trace Packet Lister: CS Decode library testing
> -----------------------------------------------
>
> ** Library Version : 0.14.4
>
> Test Command Line:-
> ./tests/bin/linux64/dbg/trc_pkt_lister   -ss_dir
> tests/snapshots/stm_only/  -src_name  ETB_1
>
> Trace Packet Lister : reading snapshot from path tests/snapshots/stm_only/
> Using ETB_1 as trace source
> Trace Packet Lister : Protocol printer STM on Trace ID 0x1
> ID:1    END OF TRACE DATA
> Trace Packet Lister : Trace buffer done, processed 16384 bytes.
>
> [1]
> https://github.com/Linaro/OpenCSD/blob/master/decoder/tests/source/trc_pkt_lister.cpp
> [2] Driver: hwtracing/stm/console.c
>
> Any help or guidance would be much appreciated.
>
> Regards,
> Ajay Bharadwaj