Commit 774daad3 authored by James Clark's avatar James Clark Committed by Suzuki K Poulose
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Documentation: coresight: Expand branch broadcast documentation 



Now that there is a way of enabling branch broadcast via perf, mention
the possible use cases and known limitations.

Signed-off-by: default avatarJames Clark <james.clark@arm.com>
Reviewed-by: default avatarMike <Leach&lt;mike.leach@linaro.org>
Signed-off-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20220511144601.2257870-5-james.clark@arm.com
parent 32ee00d8

Documentation/trace/coresight/coresight-etm4x-reference.rst

+12 −1
Original line number Diff line number Diff line
@@ -656,7 +656,18 @@ 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.



    There is currently no support in Perf for supplying modified binaries to the decoder, so this

    feature is only inteded to be used for debugging purposes or with a 3rd party tool.



    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: