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Thu, 02 Oct 2025 03:10:00 -0700 (PDT) From: James Clark Date: Thu, 02 Oct 2025 11:09:33 +0100 Subject: [PATCH v3 5/5] coresight: docs: Document etm4x ts_interval Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Message-Id: <20251002-james-cs-syncfreq-v3-5-fe5df2bf91d1@linaro.org> References: <20251002-james-cs-syncfreq-v3-0-fe5df2bf91d1@linaro.org> In-Reply-To: <20251002-james-cs-syncfreq-v3-0-fe5df2bf91d1@linaro.org> To: Suzuki K Poulose , Mike Leach , Alexander Shishkin , Jonathan Corbet , Leo Yan Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, James Clark X-Mailer: b4 0.14.0 Document how the new field is used, maximum value and the interaction with SYNC timestamps. Signed-off-by: James Clark --- Documentation/trace/coresight/coresight.rst | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/tr= ace/coresight/coresight.rst index 806699871b80..0cd83119b83f 100644 --- a/Documentation/trace/coresight/coresight.rst +++ b/Documentation/trace/coresight/coresight.rst @@ -619,6 +619,20 @@ They are also listed in the folder /sys/bus/event_sour= ce/devices/cs_etm/format/ - Cycle count threshold value. If nothing is provided here or the pro= vided value is 0, then the default value i.e 0x100 will be used. If provided value is less tha= n minimum cycles threshold value, as indicated via TRCIDR3.CCITMIN, then the minimum value wil= l be used instead. + * - ts_level + - Controls frequency of timestamps. The reload value of the + timestamp counter is 2 raised to the power of this value. If the va= lue is + 0 then the reload value is 1, if the value is 10 then the reload va= lue is + 1024. Maximum allowed value is 15, and setting the maximum disables + generation of timestamps via the counter, freeing the counter resou= rces. + Timestamps will be generated after 2 ^ ts_level cycles. + + Separately to this value, timestamps will also be emitted when a SY= NC + packet is generated, although this is only for every 4096 bytes of = trace. + Therefore it's not possible to generate timestamps less frequently = than + that and ts_level timestamps are always in addition to SYNC timesta= mps. + Timestamps must be enabled for this to have effect. + =20 How to use the STM module ------------------------- --=20 2.34.1