From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 6781E23EAA6; Wed, 26 Nov 2025 14:01:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764165719; cv=none; b=rUDLu7eFrBh+ZCMbQpXru3MUsSbxIxSW+pZ/uDEXuSAsi1A3ytVc5i2OY3q7DW5azRTgYo/RQ+ApEMPuPAJXIZc8byIpO40dvw263gG+irwUKjmKlqiA2Mvx38+yoadjDore7J5eqIOqF7Ms5fhZYxinOMJLl9pC3TLLWfGVlFc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764165719; c=relaxed/simple; bh=ai9zoFZ/rFbXtytL805Fuj+PA5zGMsbhcA5wNMOjdRk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=HNU6ydta5Uje0qT5L4Q+TZSsJoCjtvkgVV/R4WLtrPmUO5NehLSxJgBjtc80NW9AnfnJ3gL98zVASWCIPjwv603yo1+onOMsGWscMOK8KloIPEIK4mhZLQmrCgVhldhtOaqz5g8dtGWnnxE7hksjh6dvxVmpzPKNGWFV+bF1pns= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 11A77168F; Wed, 26 Nov 2025 06:01:49 -0800 (PST) Received: from localhost (e132581.arm.com [10.1.196.87]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 130FA3F73B; Wed, 26 Nov 2025 06:01:55 -0800 (PST) Date: Wed, 26 Nov 2025 14:01:54 +0000 From: Leo Yan To: James Clark Cc: Suzuki K Poulose , Mike Leach , Alexander Shishkin , Jonathan Corbet , Randy Dunlap , coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org Subject: Re: [PATCH v7 13/13] coresight: docs: Document etm4x timestamp interval option Message-ID: <20251126140154.GK724103@e132581.arm.com> References: <20251126-james-cs-syncfreq-v7-0-7fae5e0e5e16@linaro.org> <20251126-james-cs-syncfreq-v7-13-7fae5e0e5e16@linaro.org> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251126-james-cs-syncfreq-v7-13-7fae5e0e5e16@linaro.org> On Wed, Nov 26, 2025 at 10:54:42AM +0000, James Clark wrote: > Document how the new field is used, maximum value and the interaction > with SYNC timestamps. > > Signed-off-by: James Clark Reviewed-by: Leo Yan > --- > Documentation/trace/coresight/coresight.rst | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) > > diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst > index 806699871b80..d461de4e067e 100644 > --- a/Documentation/trace/coresight/coresight.rst > +++ b/Documentation/trace/coresight/coresight.rst > @@ -613,8 +613,20 @@ 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 > ` > * - timestamp > - - Session local version of the system wide setting: :ref:`ETMv4_MODE_TIMESTAMP > - ` > + - Controls generation and interval of timestamps. > + > + 0 = off, 1 = minimum interval .. 15 = maximum 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 ^ (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. > + > + Setting the maximum interval (15) will disable the counter generated > + timestamps, freeing the counter resource, leaving only ones emitted when > + a SYNC packet is generated. The sync interval is controlled with > + TRCSYNCPR.PERIOD which is every 4096 bytes of trace by default. > + > * - cc_threshold > - Cycle count threshold value. If nothing is provided here or the provided value is 0, then the > default value i.e 0x100 will be used. If provided value is less than minimum cycles threshold > > -- > 2.34.1 >