[RFC PATCH 00/24] Add Linux RISC-V trace support via the gtrace framework

[Zane Leung]

This series adds Linux RISC-V trace support via the generic hardware trace
(gtrace) framework [1].  The RISC-V trace encoder, funnel, ATB bridge, and
timestamp components are implemented as gtrace components, and the CoreSight
funnel and TMC (ETB/ETF/ETR) are likewise re-implemented as gtrace components
so that they can be composed with the RISC-V components into a single trace path.

This work supersedes the earlier CoreSight-based RFC [2]. Instead of forcing
the RISC-V trace IP to conform to the CoreSight device, this series shifts
the topology onto the gtrace framework to achieve cleaner architectural
decoupling and shared data paths.

The series includes:

- gtrace sysfs support, exposing per-component attributes (control,
  features, and timestamp) for configuration and validation
- gtrace component drivers for the RISC-V trace encoder, funnel, ATB
  bridge, and timestamp components
- gtrace component drivers for the CoreSight dynamic funnel and TMC
  (ETB/ETF/ETR), built on top of the CoreSight platform core APIs
  (CLAIM/device registration) re-implemented as gtrace components
- perf PMU support: gtrace event format attributes, per-event configuration
  parsing, and an AUX flag marking CoreSight-formatted trace data
- perf tooling: a Nexus (N-Trace) decoder and a gtrace AUX decoder that
  synthesizes branch samples, including machine-mode instruction access

Verification on K3 SoC:
The device tree follows [1], with only the compatible properties changed for
the gtrace components.

# perf list pmu
  gtrace//                                          [Kernel PMU event]

# perf record -e gtrace// --per-thread uname
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 1.946 MB perf.data ]

# perf script
uname  767863          1                          branches:  ffffffff80d18b04 gtrace_poll_bit+0x34 ([kernel.kallsyms]) => ffffffff80d18b12 gtrace_poll_bit+0x42 ([kernel.kallsyms])
uname  767863          1                          branches:  ffffffff80d18b4e gtrace_poll_bit+0x7e ([kernel.kallsyms]) => ffffffff80d18b6c gtrace_poll_bit+0x9c ([kernel.kallsyms])
uname  767863          1                          branches:  ffffffff80d1c17a rvtrace_encoder_start+0x112 ([kernel.kallsyms]) => ffffffff80d1c196 rvtrace_encoder_start+0x12e ([kernel.kallsyms])
uname  767863          1                          branches:  ffffffff80d18782 gtrace_path_start+0xbe ([kernel.kallsyms]) => ffffffff80d18702 gtrace_path_start+0x3e ([kernel.kallsyms])
uname  767863          1                          branches:  ffffffff80d18712 gtrace_path_start+0x4e ([kernel.kallsyms]) => ffffffff80d18724 gtrace_path_start+0x60 ([kernel.kallsyms])
...

In per-cpu mode, correlating trace data with the running task requires
the encoder to emit a context ID.  This depends on writing the task PID
to the RISC-V scontext CSR on context switch [3].

[1] https://lore.kernel.org/all/20260810152223.3946743-1-mayuresh.chitale@xxxxxxxxxxxxxxxx/
[2] https://lore.kernel.org/all/20260414034153.3272485-1-liangzhen@xxxxxxxxxxxxxxxxxx/
[3] https://lore.kernel.org/all/20240329-dev-maxh-lin-452-6-9-v1-0-1534f93b94a7@xxxxxxxxxx/

Zane Leung (24):
  gtrace: Move connection release into component unregister
  gtrace: Initial implementation of gtrace sysfs framework
  gtrace: Drop trace format field and helper function
  gtrace: Add RISC-V trace encoder sysfs support
  gtrace: Introduce some PMU format attributes
  gtrace: Replace owner PID with perf_event pointer in gtrace_path
  gtrace: Parse RISC-V Trace encoder config from perf event
  gtrace: add perf symlink support for gtrace components
  gtrace: Add port-level start/stop driver callbacks
  gtrace: Add RISC-V trace funnel driver
  gtrace: Add RISC-V trace timestamp support
  gtrace: Add RISC-V trace ATB bridge driver
  gtrace: Add CoreSight platform core APIs
  gtrace: Add CoreSight funnel driver
  gtrace: Only copy AUX data from the path sink
  perf: Flag whether gtrace AUX data carries CoreSight framing
  gtrace: Unify default sink selection across CPUs in perf setup
  gtrace: Add sink-specific buffer alloc/free callbacks
  gtrace: Add setup_sysfs_buf callback to setup sysfs sink buffer
  gtrace: Add CoreSight TMC driver support
  perf tools: riscv: making gtrace PMU listable
  perf tools: Add Nexus RISC-V Trace decoder
  perf tools: gtrace: Record and parse trace encoder metadata
  perf tools: gtrace: Add AUX trace decoder and branch sample synthesis

 .../hwtracing/coresight/coresight-tmc-etf.c   |    1 -
 drivers/hwtracing/gtrace/Kconfig              |   70 +
 drivers/hwtracing/gtrace/Makefile             |   12 +-
 drivers/hwtracing/gtrace/coresight-funnel.c   |  430 ++++
 drivers/hwtracing/gtrace/coresight-platform.c |  279 +++
 drivers/hwtracing/gtrace/coresight-tmc-core.c | 1111 ++++++++++
 drivers/hwtracing/gtrace/coresight-tmc-etf.c  |  573 +++++
 drivers/hwtracing/gtrace/coresight-tmc-etr.c  | 1888 +++++++++++++++++
 drivers/hwtracing/gtrace/coresight-tmc.h      |  469 ++++
 drivers/hwtracing/gtrace/coresight.h          |  212 ++
 drivers/hwtracing/gtrace/gtrace-core.c        |  165 +-
 drivers/hwtracing/gtrace/gtrace-perf.c        |  122 +-
 drivers/hwtracing/gtrace/gtrace-sysfs.c       |  452 ++++
 drivers/hwtracing/gtrace/rvtrace-atbbridge.c  |  153 ++
 ...trace-encoder.c => rvtrace-encoder-core.c} |  182 +-
 .../hwtracing/gtrace/rvtrace-encoder-sysfs.c  |  323 +++
 drivers/hwtracing/gtrace/rvtrace-encoder.h    |   61 +
 drivers/hwtracing/gtrace/rvtrace-funnel.c     |  220 ++
 drivers/hwtracing/gtrace/rvtrace-funnel.h     |   29 +
 drivers/hwtracing/gtrace/rvtrace-platform.c   |   26 +-
 drivers/hwtracing/gtrace/rvtrace-ramsink.c    |   11 +-
 drivers/hwtracing/gtrace/rvtrace-timestamp.c  |  336 +++
 drivers/hwtracing/gtrace/rvtrace-timestamp.h  |   44 +
 drivers/hwtracing/gtrace/rvtrace.h            |    5 +
 include/linux/gtrace.h                        |  161 +-
 include/uapi/linux/perf_event.h               |    1 +
 tools/arch/riscv/include/asm/insn.h           |  645 ++++++
 tools/include/uapi/linux/perf_event.h         |    1 +
 tools/perf/arch/riscv/util/Build              |    1 +
 tools/perf/arch/riscv/util/auxtrace.c         |  203 +-
 tools/perf/arch/riscv/util/pmu.c              |   19 +
 tools/perf/builtin-script.c                   |    4 +
 tools/perf/util/Build                         |    1 +
 tools/perf/util/gtrace-decoder.c              | 1283 ++++++++++-
 tools/perf/util/gtrace.h                      |   30 +-
 tools/perf/util/rvtrace-decoder/Build         |    2 +
 .../util/rvtrace-decoder/rvtrace-decoder.c    |  423 ++++
 .../util/rvtrace-decoder/rvtrace-decoder.h    |  122 ++
 .../rvtrace-decoder/rvtrace-ntrace-decoder.c  |  910 ++++++++
 .../rvtrace-decoder/rvtrace-ntrace-decoder.h  |  124 ++
 tools/perf/util/symbol_conf.h                 |    2 +
 41 files changed, 10926 insertions(+), 180 deletions(-)
 create mode 100644 drivers/hwtracing/gtrace/coresight-funnel.c
 create mode 100644 drivers/hwtracing/gtrace/coresight-platform.c
 create mode 100644 drivers/hwtracing/gtrace/coresight-tmc-core.c
 create mode 100644 drivers/hwtracing/gtrace/coresight-tmc-etf.c
 create mode 100644 drivers/hwtracing/gtrace/coresight-tmc-etr.c
 create mode 100644 drivers/hwtracing/gtrace/coresight-tmc.h
 create mode 100644 drivers/hwtracing/gtrace/coresight.h
 create mode 100644 drivers/hwtracing/gtrace/gtrace-sysfs.c
 create mode 100644 drivers/hwtracing/gtrace/rvtrace-atbbridge.c
 rename drivers/hwtracing/gtrace/{rvtrace-encoder.c => rvtrace-encoder-core.c} (55%)
 create mode 100644 drivers/hwtracing/gtrace/rvtrace-encoder-sysfs.c
 create mode 100644 drivers/hwtracing/gtrace/rvtrace-encoder.h
 create mode 100644 drivers/hwtracing/gtrace/rvtrace-funnel.c
 create mode 100644 drivers/hwtracing/gtrace/rvtrace-funnel.h
 create mode 100644 drivers/hwtracing/gtrace/rvtrace-timestamp.c
 create mode 100644 drivers/hwtracing/gtrace/rvtrace-timestamp.h
 create mode 100644 tools/arch/riscv/include/asm/insn.h
 create mode 100644 tools/perf/arch/riscv/util/pmu.c
 create mode 100644 tools/perf/util/rvtrace-decoder/Build
 create mode 100644 tools/perf/util/rvtrace-decoder/rvtrace-decoder.c
 create mode 100644 tools/perf/util/rvtrace-decoder/rvtrace-decoder.h
 create mode 100644 tools/perf/util/rvtrace-decoder/rvtrace-ntrace-decoder.c
 create mode 100644 tools/perf/util/rvtrace-decoder/rvtrace-ntrace-decoder.h

-- 
2.34.1