2012/6/29 Arve Hj?nnev?g [off-list ref]:

On Thu, Jun 28, 2012 at 8:42 AM, Linus Walleij [off-list ref] wrote:

quoted

On Thu, Jun 21, 2012 at 7:38 AM, Frank Li [off-list ref] wrote:

quoted

Anyone use ARM ETM/ETB before?

I know for sure that Arve has been making good use of the ETB+ETB,
since there are some nice patches for it in the Android source tree,
but I don't know how he's using it :-)

I have not used it a lot, but I made changes to make it work on
systems with Cortex A8, A9 and A15 cpus. I found it most useful to
debug watchdog resets, but I had to manually figure out where in the
buffer the data starts since the pointers were lost on a reset.

quoted

John Stultz recently submitted some of Arves patches upstream so let's
ask these gentlemen how they use it.

Yours,
Linus Walleij

quoted

I run.
echo 1 > /sys/devices/etm/trace_running

root at freescale /$ echo v >/proc/sysrq-trigger
SysRq : etm
Trace buffer contents length: 4

--- ETB buffer begin ---

01000000000000000000000000000000

--- ETB buffer end ---

Make sure you don't have trace-funnels between the trace cell and the
trace buffer that need to be configured. All the SOCs I used have at
least one trace funnel in the way that by default did not not pass any
data through. The driver has no code to configure these (the channels
used are SOC specific and usually not well documented).

Also, at least one SOC I used would not output any trace data with the
default configuration since it considered the kernel to be executing
in secure mode. One of the patches from the android tree fixes this.

Thank you for your reply. I will check trace-funnel with our IC team
owner and update you.
I have picked up below patch. Anything missed?

* | 2d4660b ARM: etm: Power down etm(s) when tracing is not enabled
* | 6e48ba5 ARM: etm: Support multiple ETMs/PTMs.
* | c1db5d4 ARM: etm: Return the entire trace buffer if it is empty after reset
* | 5b9dda1 ARM: etm: Add some missing locks and error checks
* | 1a6825a ARM: etm: Configure data tracing
* | 22a917b ARM: etm: Allow range selection
* | 684b02b ARM: etm: Don't try to clear the buffer full status after reading th
* | 86827c5 ARM: etm: Don't limit tracing to only non-secure code.
* | 936c25b ARM: etm: Don't require clock control

quoted

quoted

best regards
Frank Li

Yours,
Linus Walleij

--
Arve Hj?nnev?g