From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D08F9C433ED for ; Fri, 9 Apr 2021 10:38:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B2BCB610A4 for ; Fri, 9 Apr 2021 10:38:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233860AbhDIKib (ORCPT ); Fri, 9 Apr 2021 06:38:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33910 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233597AbhDIKhy (ORCPT ); Fri, 9 Apr 2021 06:37:54 -0400 Received: from mail-wm1-x32f.google.com (mail-wm1-x32f.google.com [IPv6:2a00:1450:4864:20::32f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 11F25C061760 for ; Fri, 9 Apr 2021 03:37:41 -0700 (PDT) Received: by mail-wm1-x32f.google.com with SMTP id p22so2662378wmc.3 for ; Fri, 09 Apr 2021 03:37:40 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=kWBYmHFzVaAtr0q3DL3loxqYVHyccUJehxRYe/jfvbg=; b=ARzQXpjiRt6ls9E+pAZwb5B9/UpTCQkFlIbkmnY9jYufyoDyeztU1E9HBvMk0J6d1Z qD61bGE3BS8vBFmMf5zWiwPPqrJg9VXNJqqGPuFVBsMh7MsroxvByiZdZaOO93QVgjah eGuTr4liRK/Qe58X2MA+gGbU5UEkfiyGVaf/I4RQ7/ifTEzAjbZgnRx2HYsHfIqs8pXd Ql+qKQ+GhjiB+vJwCmgXuEptLBJnp4Dmg1Dvbghk6P3DQVq9v0ZlHn48p0F/5sbfRbFH HwxbN14iOK/hQ0qjMW34FgZ2CXwnTFrPK8MBzqS4AUsfK7dVhju/iOAeped0zSlQZ3Gy TPCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=kWBYmHFzVaAtr0q3DL3loxqYVHyccUJehxRYe/jfvbg=; b=ri1Q1NcRJjWeyVDqvuLCoWA3FDNtTDG6ja34L5DAkfjZ/dip7CrZcO0WG8gItD78xE jC97fhW0gXbKSBoxzhj/V0RNaZIAGsIE+V9PpbKLWu7egsj8BnS81h+SRPuFZqGMl2yY A8jGQHc3rOx9Xrg69HRdR7a0ARauJWqqNOgw7AQXAj1ODYiK1OrkwBpEDhUrtq0zncTw VixYmJSV8PV4STRsFPjrbbWiij+HNpvtICPeg4j3BRny3TQ5p+u6j08On/yf5rVmB8OE X1WSnfLl6LwVN6N/0Hrf94EN9rVMOxnfEb4Zz2genDFThoKS8oQWbU/8mVaafZHB7/m1 sLrQ== X-Gm-Message-State: AOAM531sBeHK0kD52iZtUmuMZdgZfzEQqQsbllMwhi5aVaZDrMj5lGvz J906EjoCJaYWkSQSTuAI/QddLA== X-Google-Smtp-Source: ABdhPJya2LyjaJcGVs922z6D7INvTqlY2X2yrmG3CDn4I0ZGV/fdj9ORlhpUfz/Eog4RIFAOd01tiw== X-Received: by 2002:a1c:2587:: with SMTP id l129mr13071412wml.135.1617964659744; Fri, 09 Apr 2021 03:37:39 -0700 (PDT) Received: from linaro.org ([2a00:23c5:6809:2201:20a6:106c:24d6:628]) by smtp.gmail.com with ESMTPSA id w7sm4087650wro.43.2021.04.09.03.37.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 09 Apr 2021 03:37:39 -0700 (PDT) From: Mike Leach To: linux-arm-kernel@lists.infradead.org, coresight@lists.linaro.org, mathieu.poirier@linaro.org, linux-doc@vger.kernel.org, suzuki.poulose@arm.com Cc: yabinc@google.com, leo.yan@linaro.org, alexander.shishkin@linux.intel.com, tingwei@codeaurora.org, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org, Mike Leach , Jonathan Corbet Subject: [PATCH v6 10/10] Documentation: coresight: Add documentation for CoreSight config Date: Fri, 9 Apr 2021 11:37:22 +0100 Message-Id: <20210409103722.26290-11-mike.leach@linaro.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20210409103722.26290-1-mike.leach@linaro.org> References: <20210409103722.26290-1-mike.leach@linaro.org> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Adds documentation for the CoreSight System configuration manager. Cc: Jonathan Corbet Cc: linux-doc@vger.kernel.org Signed-off-by: Mike Leach Reviewed-by: Mathieu Poirier --- .../trace/coresight/coresight-config.rst | 244 ++++++++++++++++++ Documentation/trace/coresight/coresight.rst | 16 ++ 2 files changed, 260 insertions(+) create mode 100644 Documentation/trace/coresight/coresight-config.rst diff --git a/Documentation/trace/coresight/coresight-config.rst b/Documentation/trace/coresight/coresight-config.rst new file mode 100644 index 000000000000..a4e3ef295240 --- /dev/null +++ b/Documentation/trace/coresight/coresight-config.rst @@ -0,0 +1,244 @@ +.. SPDX-License-Identifier: GPL-2.0 + +====================================== +CoreSight System Configuration Manager +====================================== + + :Author: Mike Leach + :Date: October 2020 + +Introduction +============ + +The CoreSight System Configuration manager is an API that allows the +programming of the CoreSight system with pre-defined configurations that +can then be easily enabled from sysfs or perf. + +Many CoreSight components can be programmed in complex ways - especially ETMs. +In addition, components can interact across the CoreSight system, often via +the cross trigger components such as CTI and CTM. These system settings can +be defined and enabled as named configurations. + + +Basic Concepts +============== + +This section introduces the basic concepts of a CoreSight system configuration. + + +Features +-------- + +A feature is a named set of programming for a CoreSight device. The programming +is device dependent, and can be defined in terms of absolute register values, +resource usage and parameter values. + +The feature is defined using a descriptor. This descriptor is used to load onto +a matching device, either when the feature is loaded into the system, or when the +CoreSight device is registered with the configuration manager. + +The load process involves interpreting the descriptor into a set of register +accesses in the driver - the resource usage and parameter descriptions +translated into appropriate register accesses. This interpretation makes it easy +and efficient for the feature to be programmed onto the device when required. + +The feature will not be active on the device until the feature is enabled, and +the device itself is enabled. When the device is enabled then enabled features +will be programmed into the device hardware. + +A feature is enabled as part of a configuration being enabled on the system. + + +Parameter Value +~~~~~~~~~~~~~~~ + +A parameter value is a named value that may be set by the user prior to the +feature being enabled that can adjust the behaviour of the operation programmed +by the feature. + +For example, this could be a count value in a programmed operation that repeats +at a given rate. When the feature is enabled then the current value of the +parameter is used in programming the device. + +The feature descriptor defines a default value for a parameter, which is used +if the user does not supply a new value. + +Users can update parameter values using the configfs API for the CoreSight +system - which is described below. + +The current value of the parameter is loaded into the device when the feature +is enabled on that device. + + +Configurations +-------------- + +A configuration defines a set of features that are to be used in a trace +session where the configuration is selected. For any trace session only one +configuration may be selected. + +The features defined may be on any type of device that is registered +to support system configuration. A configuration may select features to be +enabled on a class of devices - i.e. any ETMv4, or specific devices, e.g. a +specific CTI on the system. + +As with the feature, a descriptor is used to define the configuration. +This will define the features that must be enabled as part of the configuration +as well as any preset values that can be used to override default parameter +values. + + +Preset Values +~~~~~~~~~~~~~ + +Preset values are easily selectable sets of parameter values for the features +that the configuration uses. The number of values in a single preset set, equals +the sum of parameter values in the features used by the configuration. + +e.g. a configuration consists of 3 features, one has 2 parameters, one has +a single parameter, and another has no parameters. A single preset set will +therefore have 3 values. + +Presets are optionally defined by the configuration, up to 15 can be defined. +If no preset is selected, then the parameter values defined in the feature +are used as normal. + + +Operation +~~~~~~~~~ + +The following steps take place in the operation of a configuration. + +1) In this example, the configuration is 'autofdo', which has an + associated feature 'strobing' that works on ETMv4 CoreSight Devices. + +2) The configuration is enabled. For example 'perf' may select the + configuration as part of its command line:: + + perf record -e cs_etm/autofdo/ myapp + + which will enable the 'autofdo' configuration. + +3) perf starts tracing on the system. As each ETMv4 that perf uses for + trace is enabled, the configuration manager will check if the ETMv4 + has a feature that relates to the currently active configuration. + In this case 'strobing' is enabled & programmed into the ETMv4. + +4) When the ETMv4 is disabled, any registers marked as needing to be + saved will be read back. + +5) At the end of the perf session, the configuration will be disabled. + + +Viewing Configurations and Features +=================================== + +The set of configurations and features that are currently loaded into the +system can be viewed using the configfs API. + +Mount configfs as normal and the 'cs-syscfg' subsystem will appear:: + + $ ls /config + cs-syscfg stp-policy + +This has two sub-directories:: + + $ cd cs-syscfg/ + $ ls + configurations features + +The system has the configuration 'autofdo' built in. It may be examined as +follows:: + + $ cd configurations/ + $ ls + autofdo + $ cd autofdo/ + $ ls + description preset1 preset3 preset5 preset7 preset9 + feature_refs preset2 preset4 preset6 preset8 + $ cat description + Setup ETMs with strobing for autofdo + $ cat feature_refs + strobing + +Each preset declared has a preset subdirectory declared. The values for +the preset can be examined:: + + $ cat preset1/values + strobing.window = 0x1388 strobing.period = 0x2 + $ cat preset2/values + strobing.window = 0x1388 strobing.period = 0x4 + +The features referenced by the configuration can be examined in the features +directory:: + + $ cd ../../features/strobing/ + $ ls + description matches nr_params params + $ cat description + Generate periodic trace capture windows. + parameter 'window': a number of CPU cycles (W) + parameter 'period': trace enabled for W cycles every period x W cycles + $ cat matches + SRC_ETMV4 + $ cat nr_params + 2 + +Move to the params directory to examine and adjust parameters:: + + cd params + $ ls + period window + $ cd period + $ ls + value + $ cat value + 0x2710 + # echo 15000 > value + # cat value + 0x3a98 + +Parameters adjusted in this way are reflected in all device instances that have +loaded the feature. + + +Using Configurations in perf +============================ + +The configurations loaded into the CoreSight configuration management are +also declared in the perf 'cs_etm' event infrastructure so that they can +be selected when running trace under perf:: + + $ ls /sys/devices/cs_etm + configurations format perf_event_mux_interval_ms sinks type + events nr_addr_filters power + +Key directories here are 'configurations' - which lists the loaded +configurations, and 'events' - a generic perf directory which allows +selection on the perf command line.:: + + $ ls configurations/ + autofdo + $ cat configurations/autofdo + 0xa7c3dddd + +As with the sinks entries, this provides a hash of the configuration name. +The entry in the 'events' directory uses perfs built in syntax generator +to substitute the syntax for the name when evaluating the command:: + + $ ls events/ + autofdo + $ cat events/autofdo + configid=0xa7c3dddd + +The 'autofdo' configuration may be selected on the perf command line:: + + $ perf record -e cs_etm/autofdo/u --per-thread + +A preset to override the current parameter values can also be selected:: + + $ perf record -e cs_etm/autofdo,preset=1/u --per-thread + +When configurations are selected in this way, then the trace sink used is +automatically selected. diff --git a/Documentation/trace/coresight/coresight.rst b/Documentation/trace/coresight/coresight.rst index 169749efd8d1..7ec656c9f0dc 100644 --- a/Documentation/trace/coresight/coresight.rst +++ b/Documentation/trace/coresight/coresight.rst @@ -619,6 +619,20 @@ A separate documentation file is provided to explain the use of these devices. (:doc:`coresight-ect`) [#fourth]_. +CoreSight System Configuration +------------------------------ + +CoreSight components can be complex devices with many programming options. +Furthermore, components can be programmed to interact with each other across the +complete system. + +A CoreSight System Configuration manager is provided to allow these complex programming +configurations to be selected and used easily from perf and sysfs. + +See the separate document for further information. +(:doc:`coresight-config`) [#fifth]_. + + .. [#first] Documentation/ABI/testing/sysfs-bus-coresight-devices-stm .. [#second] Documentation/trace/stm.rst @@ -626,3 +640,5 @@ A separate documentation file is provided to explain the use of these devices. .. [#third] https://github.com/Linaro/perf-opencsd .. [#fourth] Documentation/trace/coresight/coresight-ect.rst + +.. [#fifth] Documentation/trace/coresight/coresight-config.rst -- 2.17.1