linux-kernel - Re: [PATCH 00/19] coresight: trbe: Support trigger and circle buffer modes

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Message-ID: <ae9aacb1-29ae-4e05-ac55-0db555c3e455@arm.com>
Date: Fri, 5 Dec 2025 10:23:54 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Leo Yan <leo.yan@....com>, Suzuki K Poulose <suzuki.poulose@....com>,
 Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>,
 Yeoreum Yun <yeoreum.yun@....com>, Will Deacon <will@...nel.org>,
 Mark Rutland <mark.rutland@....com>, Tamas Petz <tamas.petz@....com>,
 Tamas Zsoldos <tamas.zsoldos@....com>,
 Arnaldo Carvalho de Melo <acme@...nel.org>,
 Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>,
 Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 00/19] coresight: trbe: Support trigger and circle buffer
 modes

On 01/12/25 4:51 PM, Leo Yan wrote:
> The current TRBE driver operates only in fill mode, where tracing stops
> at the top of buffer and a maintenance interrupt is raised.  Due to
> interrupt latency, tracing is halted while the program continues to run,
> resulting in trace data lose.
> 
> This series enhances the driver for the trigger mode to mitigate trace
> discontinuity.  The circle buffer mode is introduced to avoid any
> maintenance interrupts during the snapshot session.
> 
> It can be divided into three parts for easier review:
> 
>   Patches 01~05: Minor refactoring for disabling operations and
>                  clearing status.

Could these patches be posted first ?

>   Patches 06~12: Refactor fault action and trace size calculation.

Followed by this set which still keeps the existing functionality intact.

>   Patches 13~19: Support trigger and circle modes. To better utilize the
>                  new buffer modes, perf sets the watermark to
> 		 one-quarter of the buffer size.

Then finally all above changes which are newer functions and tests etc.

I guess that will be much easier to review.

> 
> This series is applied on coresight-next branch and has been validated
> on Orion O6 board:
> 
>   1) The trigger count and wrap mode are verified using Ftrace logs.
>   2) A new kunit test module verifies limit and count calculations.
>   3) Basic perf record / script commands and module load/unload have
>      been tested successfully.
> 
> Signed-off-by: Leo Yan <leo.yan@....com>
> ---
> Leo Yan (19):
>       coresight: trbe: Use helpers for checking errata
>       coresight: trbe: Remove redundant disable operation
>       coresight: trbe: Remove buffer disabling in trbe_handle_overflow()
>       coresight: trbe: Remove set_trbe_disabled() from the enable flow
>       coresight: trbe: Refactor status clearing
>       coresight: trbe: Refactor syndrome decoding
>       coresight: trbe: Refactor AUX flag setting
>       coresight: trbe: Use PERF_AUX_FLAG_PARTIAL instead of PERF_AUX_FLAG_COLLISION
>       coresight: trbe: Add fault action argument to trbe_handle_overflow()
>       coresight: trbe: Always check fault action when updating buffer
>       coresight: trbe: Apply overwrite erratum for only wrap event
>       coresight: trbe: Calculate size for buffer wrapping
>       coresight: trbe: Remove misleading comment
>       coresight: trbe: Refactor compute_trbe_buffer_limit()
>       coresight: trbe: Add static key for bypassing trigger mode
>       coresight: trbe: Support trigger mode
>       coresight: trbe: Enable circle mode for snapshot
>       coresight: trbe: Add kunit tests
>       perf: cs-etm: Set watermark for AUX trace
> 
>  drivers/hwtracing/coresight/Kconfig                |   9 +
>  drivers/hwtracing/coresight/Makefile               |   1 +
>  .../coresight/coresight-trbe-kunit-tests.c         | 536 +++++++++++++++++++++
>  drivers/hwtracing/coresight/coresight-trbe.c       | 440 +++++++++--------
>  drivers/hwtracing/coresight/coresight-trbe.h       | 111 ++++-
>  tools/perf/arch/arm/util/cs-etm.c                  |   7 +
>  6 files changed, 896 insertions(+), 208 deletions(-)
> ---
> base-commit: 9e9182cab5ebc3ee7544e60ef08ba19fdf216920
> change-id: 20251120-trbe_buffer_refactor_v1-1-8f8023105469
> 
> Best regards,