[PATCH RFC 0/2] Add basic tracing support for m68k

[Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxx>]

In order to debug latency issues, I wanted to use ftrace on my M54418
coldfire. Sadly, it is not supported yet.
Thanks to Steven [1] it does not sound too difficult.

This small series adds basic functions to make it work, and for the few
tests I could do, it seems to be working well.

Here is a simple output I get:

```

            bash-232     [000] d..3.   947.629000: thread_noise:     bash:232 start 947.629000000 duration 0 ns
      timerlat/0-274     [000] .....   947.629000: #51598 context thread timer_latency    409280 ns
            bash-232     [000] d.h..   947.630000: #51599 context    irq timer_latency    110720 ns
            bash-232     [000] dnh1.   947.630000: irq_noise: timer:206 start 947.629000000 duration 1000000 ns
            bash-232     [000] d..3.   947.630000: thread_noise:     bash:232 start 947.630000000 duration 0 ns
      timerlat/0-274     [000] .....   947.630000: #51599 context thread timer_latency    407168 ns
            bash-232     [000] d.h..   947.631000: #51600 context    irq timer_latency    108608 ns
            bash-232     [000] dnh1.   947.631000: irq_noise: timer:206 start 947.630000000 duration 1000000 ns
            bash-232     [000] d..3.   947.631000: thread_noise:     bash:232 start 947.631000000 duration 0 ns
      timerlat/0-274     [000] .....   947.631000: #51600 context thread timer_latency    401472 ns
```

I am very interested by any relevant test to do (switch events ?
Anything else ?) to improve the series (and the platform :-)).

I am quite sure I missed a *lot* of things, but it seems to do what I
need :-). I post it as RFC for now, in particular because I added a new
file, and I am not sure if it is the proper way.

Thanks for your remarks and improvements !

[1]: https://lore.kernel.org/linux-m68k/20241018124511.70d29198@xxxxxxxxxxxxxxxxxx

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxx>
---
Jean-Michel Hautbois (2):
      m68k: Add tracirqs
      arch: m68k: Add STACKTRACE support

 arch/m68k/Kconfig             |  6 ++++
 arch/m68k/kernel/Makefile     |  1 +
 arch/m68k/kernel/irq.c        |  2 ++
 arch/m68k/kernel/stacktrace.c | 70 +++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 79 insertions(+)
---
base-commit: 42f7652d3eb527d03665b09edac47f85fb600924
change-id: 20241021-add-m68k-tracing-support-36c18d2233d8

Best regards,
-- 
Jean-Michel Hautbois <jeanmichel.hautbois@xxxxxxxxxx>