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From: Randy Dunlap <rdunlap@infradead.org>
To: James Clark <james.clark@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Mike Leach <mike.leach@linaro.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jonathan Corbet <corbet@lwn.net>, Leo Yan <leo.yan@arm.com>
Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org
Subject: Re: [PATCH v4 13/13] coresight: docs: Document etm4x timestamp interval option
Date: Thu, 13 Nov 2025 21:02:13 -0800	[thread overview]
Message-ID: <0eb1a2b7-8064-4ac5-bcf8-b4898a8b5ac7@infradead.org> (raw)
In-Reply-To: <20251112-james-cs-syncfreq-v4-13-165ba21401dc@linaro.org>



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@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



  reply	other threads:[~2025-11-14  5:02 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2025-11-12 15:22 [PATCH v4 00/13] coresight: Update timestamp attribute to be an interval instead of bool James Clark
2025-11-12 15:22 ` [PATCH v4 01/13] coresight: Change syncfreq to be a u8 James Clark
2025-11-14 12:20   ` Leo Yan
2025-11-12 15:22 ` [PATCH v4 02/13] coresight: Repack struct etmv4_drvdata James Clark
2025-11-12 15:22 ` [PATCH v4 03/13] coresight: Refactor etm4_config_timestamp_event() James Clark
2025-11-12 15:22 ` [PATCH v4 04/13] coresight: Hide unused ETMv3 format attributes James Clark
2025-11-14 14:55   ` Leo Yan
2025-11-18 14:56     ` James Clark
2025-11-12 15:22 ` [PATCH v4 05/13] coresight: Define format attributes with GEN_PMU_FORMAT_ATTR() James Clark
2025-11-14 15:03   ` Leo Yan
2025-11-12 15:22 ` [PATCH v4 06/13] coresight: Interpret ETMv3 config with ATTR_CFG_GET_FLD() James Clark
2025-11-14 15:07   ` Leo Yan
2025-11-12 15:22 ` [PATCH v4 07/13] coresight: Don't reject unrecognized ETMv3 format attributes James Clark
2025-11-14 15:18   ` Leo Yan
2025-11-14 15:21     ` James Clark
2025-11-12 15:22 ` [PATCH v4 08/13] coresight: Interpret perf config with ATTR_CFG_GET_FLD() James Clark
2025-11-14 15:30   ` Leo Yan
2025-11-14 15:34     ` James Clark
2025-11-14 15:41       ` Leo Yan
2025-11-12 15:22 ` [PATCH v4 09/13] coresight: Interpret ETMv4 " James Clark
2025-11-14 16:09   ` Leo Yan
2025-11-12 15:22 ` [PATCH v4 10/13] coresight: Remove misleading definitions James Clark
2025-11-14 16:23   ` Leo Yan
2025-11-12 15:22 ` [PATCH v4 11/13] coresight: Extend width of timestamp format attribute James Clark
2025-11-14 17:10   ` Leo Yan
2025-11-12 15:22 ` [PATCH v4 12/13] coresight: Allow setting the timestamp interval James Clark
2025-11-12 15:22 ` [PATCH v4 13/13] coresight: docs: Document etm4x timestamp interval option James Clark
2025-11-14  5:02   ` Randy Dunlap [this message]
2025-11-14  9:59     ` James Clark
2025-11-14 18:05   ` Leo Yan
2025-11-18 16:15     ` James Clark

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