target: allow profiling from running

target: allow profiling from running

There are a handful of implementations of profiling. There is the
default implementation, which repeatedly halts and resumes the target,
sampling PC each time. There is the Cortex-M implementation, which
uses PCSR if available, otherwise falling back to halting and resuming
and sampling PC. There is the OR1K implementation, which reads NPC
repeatedly. Finally, there is the NDS32 implementation which uses some
kind of AICE commands with which I am unfamiliar.

None of these (with the possible exception of the NDS32
implementation) actually require the target to be halted when starting
profiling. The Cortex-M and OR1K actually resume the target as pretty
much their first action. The default implementation doesn’t do this,
but is written in such a way that the target just flips back and forth
between halted and running, and the code will do the right thing from
either initial state. The NDS32 implementation I don’t know about.

As such, for everything except NDS32, it is not really necessary that
the target be halted to start profiling. For the non-PCSR Cortex-M and
default implementations, there is no real harm in such a requirement,
because profiling is intrusive anyway, but there is no benefit. For
the PCSR-based Cortex-M and the OR1K, requiring that the target is
halted is annoying because it makes profiling more intrusive.

Remove the must-be-halted check from the target_profiling function.
Add it to the NDS32 implementation because I am not sure if that will
break when invoked with a running target. Do not add it to any of the
other implementations because they don’t need it.

Change-Id: I479dce999a80eccccfd3be4fa192c904f0a45709
Signed-off-by: Christopher Head <chead@zaber.com>
Reviewed-on: http://openocd.zylin.com/5235
Tested-by: jenkins
Reviewed-by: Tarek BOCHKATI <tarek.bouchkati@gmail.com>
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>