[PATCH v4 13/13] coresight: docs: Document etm4x timestamp interval option
Randy Dunlap
rdunlap at infradead.org
Thu Nov 13 21:02:13 PST 2025
On 11/12/25 7:22 AM, James Clark wrote:
> Document how the new field is used, maximum value and the interaction
> with SYNC timestamps.
>
> Signed-off-by: James Clark <james.clark at linaro.org>
> ---
> Documentation/trace/coresight/coresight.rst | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst
> index 806699871b80..80b5ed09d69b 100644
> --- a/Documentation/trace/coresight/coresight.rst
> +++ b/Documentation/trace/coresight/coresight.rst
> @@ -613,8 +613,19 @@ They are also listed in the folder /sys/bus/event_source/devices/cs_etm/format/
> - Session local version of the system wide setting: :ref:`ETM_MODE_RETURNSTACK
> <coresight-return-stack>`
> * - timestamp
> - - Session local version of the system wide setting: :ref:`ETMv4_MODE_TIMESTAMP
> - <coresight-timestamp>`
> + - Controls generation and interval of timestamps.
> +
> + 0 = off, 1 = maximum interval .. 15 = minimum interval.
> +
> + Values 1 - 14 use a counter that decrements every cycle to generate a
> + timestamp on underflow. The reload value for the counter is 2 raised to
> + the power of timestamp interval - 1. If the value is 1 then the reload
> + value is 1, if the value is 11 then the reload value is 1024 etc.
value = 11: 2^11-1 = 2047
Maybe add some parens?
--
~Randy
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