[PATCH V2 0/4] Integration of function trace with System Trace IP blocks

[Chunyan Zhang]

IP blocks allowing a variety of trace sources to log debugging
information to a pre-defined area have been introduced on a couple of
architecture [1][2]. These system trace blocks (also known as STM)
typically follow the MIPI STPv2 protocol [3] and provide a system wide
logging facility to any device, running a kernel or not, with access
to the block's log entry port(s).  Since each trace message has a
timestamp, it is possible to correlate events happening in the entire
system rather than being confined to the logging facility of a single
entity.

This patchset is trying to use STM IP blocks to collect some function
tracing information produced by Ftrace.  Since writing STM is relatively
time-consuming, my thought is that export as much useful information as
possible while using a limited bytes, in this patchset only function
pointers were copied to STM.

That way logging information generated by the function trace subsystem
and gathered in the coresight sink can be used in conjunction with
trace data from other board components, also collected in the same
trace sink.  This example is using ARM coresight STM but the same would
apply to any architecture wishing to do the same.

Comments and advice would be greatly appreciated.

Thanks,
Chunyan

[1]. https://lwn.net/Articles/674746/
[2]. http://lxr.free-electrons.com/source/drivers/hwtracing/intel_th/
[3]. http://mipi.org/specifications/debug#STP
[4]. http://lxr.free-electrons.com/source/include/linux/stm.h

Changes v2:
* Addressed comments from Alexander Shishkin:
 - Modified some ambiguous change logs.
 - Decoupled stm_ftrace and trace_output interface to STM.
 - Changed the file name from stm_ftrace.c to stm/ftrace.c.
 - Implemented link/unlink hooks for stm_ftrace.
* Removed useless header file include from stm/ftrace.c
* Added Acked-by from Steven Rostedt on 4/4.

Chunyan Zhang (4):
  trace: Introduce an output interface from ftrace to STM
  STM Ftrace: Adding generic buffer interface driver
  trace: duplicate function pointer to STM
  stm: Mark the functions of writing buffer with notrace

 drivers/hwtracing/coresight/coresight-stm.c |  2 +-
 drivers/hwtracing/intel_th/sth.c            | 11 +++--
 drivers/hwtracing/stm/Kconfig               | 10 ++++
 drivers/hwtracing/stm/Makefile              |  2 +
 drivers/hwtracing/stm/core.c                |  7 +--
 drivers/hwtracing/stm/dummy_stm.c           |  2 +-
 drivers/hwtracing/stm/ftrace.c              | 77 +++++++++++++++++++++++++++++
 include/linux/stm.h                         | 11 ++++-
 include/linux/trace_output_stm.h            | 17 +++++++
 kernel/trace/Makefile                       |  1 +
 kernel/trace/trace.c                        |  5 +-
 kernel/trace/trace_output_stm.c             | 41 +++++++++++++++
 12 files changed, 174 insertions(+), 12 deletions(-)
 create mode 100644 drivers/hwtracing/stm/ftrace.c
 create mode 100644 include/linux/trace_output_stm.h
 create mode 100644 kernel/trace/trace_output_stm.c

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1.9.1