a4271827e6
Prior to Armv8.4, the feature FEAT_TRF is not supported by Arm CPUs. Consequently, the sysfs node 'ts_source' will not be set as 1 by the CoreSight ETM driver. On the other hand, the perf tool relies on the 'ts_source' node to determine whether the kernel timestamp is traced. Since the 'ts_source' is not set for Arm CPUs prior to Armv8.4, platforms in this case cannot utilize the traced timestamp as the kernel time. This patch enables the 'T' itrace option, which forcibly utilizes the traced timestamp as the kernel time. If users are aware that their working platform's Arm CoreSight shares the same counter with the kernel time, they can specify 'T' option to decode the traced timestamp as the kernel time. An usage example is: # perf record -e cs_etm// -- test_program # perf script --itrace=i10ibT # perf report --itrace=i10ibT Reviewed-by: James Clark <james.clark@arm.com> Signed-off-by: Leo Yan <leo.yan@linaro.org> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Ian Rogers <irogers@google.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: John Garry <john.g.garry@oracle.com> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mike Leach <mike.leach@linaro.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Suzuki Poulouse <suzuki.poulose@arm.com> Cc: Will Deacon <will@kernel.org> Cc: coresight@lists.linaro.org Cc: linux-arm-kernel@lists.infradead.org Link: https://lore.kernel.org/r/20231014074513.1668000-3-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.