linux-kernel - Re: [PATCH v2 0/6] coresight: Add format attribute for setting the timestamp interval

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Message-ID: <20250930152020.GL7985@e132581.arm.com>
Date: Tue, 30 Sep 2025 16:20:20 +0100
From: Leo Yan <leo.yan@....com>
To: James Clark <james.clark@...aro.org>
Cc: Suzuki K Poulose <suzuki.poulose@....com>,
	Mike Leach <mike.leach@...aro.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jonathan Corbet <corbet@....net>, coresight@...ts.linaro.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH v2 0/6] coresight: Add format attribute for setting the
 timestamp interval

On Thu, Aug 14, 2025 at 11:49:51AM +0100, James Clark wrote:

[...]

> This is added as an event format attribute, rather than a Coresight
> config because it's something that the driver is already configuring
> automatically in Perf mode with any unused counter, so it's not possible
> to modify this with a config.

Tested on Juno-r2 for this series:

  # /mnt/build/perf record -e cs_etm/timestamp=1,ts_level=15/ -- ls
  # /mnt/build/perf script -D | grep I_TIMESTAMP | wc

   1305   11745   83337

  # /mnt/build/perf record -e cs_etm/timestamp=1,ts_level=0/ -- ls
  # /mnt/build/perf script -D | grep I_TIMESTAMP | wc

   120668 1086012 7705024

We can see a small counter (2 ^ 0 = 1) that records significant
timestamp packets.

Tested-by: Leo Yan <leo.yan@....com>