[RFC PATCH 00/24] Add Linux RISC-V trace support via the gtrace framework
Zane Leung
liangzhen at linux.spacemit.com
Thu Oct 22 20:14:41 PDT 2026
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@oss.qualcomm.com/
[2] https://lore.kernel.org/all/20260414034153.3272485-1-liangzhen@linux.spacemit.com/
[3] https://lore.kernel.org/all/20240329-dev-maxh-lin-452-6-9-v1-0-1534f93b94a7@sifive.com/
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
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