[PATCH v2 6/6] Documentation: coresight: Expand branch broadcast documentation
From: James Clark <hidden>
Date: 2022-01-13 09:11:35
Also in:
linux-doc, linux-perf-users, lkml
Subsystem:
arm/coresight framework and drivers, documentation, the rest, tracing · Maintainers:
Suzuki K Poulose, Jonathan Corbet, Linus Torvalds, Steven Rostedt, Masami Hiramatsu
Now that there is a way of enabling branch broadcast via perf, mention the possible use cases and known limitations. Signed-off-by: James Clark <redacted> --- .../trace/coresight/coresight-etm4x-reference.rst | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/Documentation/trace/coresight/coresight-etm4x-reference.rst b/Documentation/trace/coresight/coresight-etm4x-reference.rst
index 0439b4006227..ec336575919c 100644
--- a/Documentation/trace/coresight/coresight-etm4x-reference.rst
+++ b/Documentation/trace/coresight/coresight-etm4x-reference.rst@@ -656,7 +656,15 @@ Bit assignments shown below:- ETM_MODE_BB **description:** - Set to enable branch broadcast if supported in hardware [IDR0]. + Set to enable branch broadcast if supported in hardware [IDR0]. The primary use for this feature + is when code is patched dynamically at run time and the full program flow may not be able to be + reconstructed using only conditional branches. + + Choosing this option will result in a significant increase in the amount of trace generated - + possible danger of overflows, or fewer instructions covered. Note, that this option also + overrides any setting of :ref:`ETM_MODE_RETURNSTACK <coresight-return-stack>`, so where a branch + broadcast range overlaps a return stack range, return stacks will not be available for that + range. .. _coresight-cycle-accurate:
--
2.28.0
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