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documentation: trace: Clarification of perf usage with coresight.

Message ID 1490042178-2547-1-git-send-email-mike.leach@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Mike Leach March 20, 2017, 8:36 p.m. UTC 
Update to the coresight.txt documentation to clarify the specification
of the trace sink when using 'perf record'

Signed-off-by: Mike Leach <mike.leach@linaro.org>
---
 Documentation/trace/coresight.txt | 6 ++++++
 1 file changed, 6 insertions(+)
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Patch

diff --git a/Documentation/trace/coresight.txt b/Documentation/trace/coresight.txt
index d1033aa..e8af562 100644
--- a/Documentation/trace/coresight.txt
+++ b/Documentation/trace/coresight.txt
@@ -243,6 +243,12 @@  linaro@linaro-nano:~$ perf record -e cs_etm//u --per-thread <command>
 
 linaro@linaro-nano:~$ perf record -C 0,2-3 -e cs_etm//k <command>
 
+Note that after a trace run, the sink will be disabled, so it must be
+re-enabled before the next 'perf record' command is executed.
+Alternatively the sink may be specified as part of the perf command line:
+
+linaro@linaro-nano:~$ perf record -e cs_etm/@20010000.etb/u --per-thread <command>
+
 As of this writing two ETM/PTM specific options have are available: cycle
 accurate and timestamp (please refer to the Embedded Trace Macrocell reference
 manual for details on these options).  By default both are disabled but using