From patchwork Mon Jan 7 07:13:23 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: durgadoss.r@intel.com X-Patchwork-Id: 1940011 X-Patchwork-Delegate: rui.zhang@intel.com Return-Path: X-Original-To: patchwork-linux-pm@patchwork.kernel.org Delivered-To: patchwork-process-083081@patchwork1.kernel.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by patchwork1.kernel.org (Postfix) with ESMTP id 5BD653FE37 for ; Mon, 7 Jan 2013 07:19:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753740Ab3AGHSe (ORCPT ); Mon, 7 Jan 2013 02:18:34 -0500 Received: from mga03.intel.com ([143.182.124.21]:19149 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753706Ab3AGHSc (ORCPT ); Mon, 7 Jan 2013 02:18:32 -0500 Received: from azsmga001.ch.intel.com ([10.2.17.19]) by azsmga101.ch.intel.com with ESMTP; 06 Jan 2013 23:18:32 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.84,422,1355126400"; d="scan'208";a="240732819" Received: from dr3-desktop.iind.intel.com ([10.223.107.127]) by azsmga001.ch.intel.com with ESMTP; 06 Jan 2013 23:18:29 -0800 From: Durgadoss R To: rui.zhang@intel.com, linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, eduardo.valentin@ti.com, hongbo.zhang@linaro.org, wni@nvidia.com, Durgadoss R Subject: [PATCH 6/9] Thermal: Add Documentation to new APIs Date: Mon, 7 Jan 2013 12:43:23 +0530 Message-Id: <1357542806-20449-7-git-send-email-durgadoss.r@intel.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1357542806-20449-1-git-send-email-durgadoss.r@intel.com> References: <1357542806-20449-1-git-send-email-durgadoss.r@intel.com> Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org This patch adds Documentation for the new APIs introduced in this patch set. The documentation also has a model sysfs structure for reference. Signed-off-by: Durgadoss R --- Documentation/thermal/sysfs-api2.txt | 248 ++++++++++++++++++++++++++++++++++ 1 file changed, 248 insertions(+) create mode 100644 Documentation/thermal/sysfs-api2.txt diff --git a/Documentation/thermal/sysfs-api2.txt b/Documentation/thermal/sysfs-api2.txt new file mode 100644 index 0000000..ffd0402 --- /dev/null +++ b/Documentation/thermal/sysfs-api2.txt @@ -0,0 +1,248 @@ +Thermal Framework +----------------- + +Written by Durgadoss R +Copyright (c) 2012 Intel Corporation + +Created on: 4 November 2012 +Updated on: 18 December 2012 + +0. Introduction +--------------- +The Linux thermal framework provides a set of interfaces for thermal +sensors and thermal cooling devices (fan, processor...) to register +with the thermal management solution and to be a part of it. + +This document focuses on how to enable new thermal sensors and cooling +devices to participate in thermal management. This solution is intended +to be 'light-weight' and platform/architecture independent. Any thermal +sensor/cooling device should be able to use the infrastructure easily. + +The goal of thermal framework is to expose the thermal sensor/zone and +cooling device attributes in a consistent way. This will help the +thermal governors to make use of the information to manage platform +thermals efficiently. + +The thermal sensor source file can be generic (can be any sensor driver, +in any subsystem). This driver will use the sensor APIs and register with +thermal framework to participate in platform Thermal management. This +does not (and should not) know about which zone it belongs to, or any +other information about platform thermals. A sensor driver is a standalone +piece of code, which can optionally register with thermal framework. + +However, for any platform, there should be a platformX_thermal.c file, +which will know about the platform thermal characteristics (like how many +sensors, zones, cooling devices, etc.. And how they are related to each other +i.e the mapping information). Only in this file, the zone level APIs should +be used, in which case the file will have all information required to attach +various sensors to a particular zone. + +This way, we can have one platform level thermal file, which can support +multiple platforms (may be)using the same set of sensors (but)binded in +a different way. This file can get the platform thermal information +through Firmware, ACPI tables, device tree etc. + +Unfortunately, today we don't have many drivers that can be clearly +differentiated as 'sensor_file.c' and 'platform_thermal_file.c'. +But very soon we will need/have. The reason I am saying this is because +we are seeing a lot of chip drivers, starting to use thermal framework, +and we should keep it really light-weight for them to do so. + +An Example: drivers/hwmon/emc1403.c - a generic thermal chip driver +In one platform this sensor can belong to 'ZoneA' and in another the +same can belong to 'ZoneB'. But, emc1403.c does not really care about +where does it belong. It just reports temperature. + +1. Terminology +-------------- +This section describes the terminology used in the rest of this +document as well as the thermal framework code. + +thermal_sensor: Hardware that can report temperature of a particular + spot in the platform, where it is placed. The temperature + reported by the sensor is the 'real' temperature reported + by the hardware. +thermal_zone: A virtual area on the device, that gets heated up. It may + have one or more thermal sensors attached to it. +cooling_device: Any component that can help in reducing the temperature of + a 'hot spot' either by reducing its performance (passive + cooling) or by other means(Active cooling E.g. Fan) + +trip_points: Various temperature levels for each sensor. As of now, we + have four levels namely active, passive, hot and critical. + Hot and critical trip point support only one value whereas + active and passive can have any number of values. These + temperature values can come from platform data, and are + exposed through sysfs in a consistent manner. Stand-alone + thermal sensor drivers are not expected to know these values. + These values are RO. +thresholds: These are programmable temperature limits, on reaching which + the thermal sensor generates an interrupt. The framework is + notified about this interrupt to take appropriate action. + There can be as many number of thresholds as that of the + hardware supports. These values are RW. + +thermal_map: This provides the mapping (aka binding) information between + various sensors and cooling devices in a particular zone. + Typically, this also comes from platform data; Stand-alone + sensor drivers or cooling device drivers are not expected + to know these mapping information. + +2. Thermal framework APIs +------------------------- +2.1: For Thermal Sensors +2.1.1 thermal_sensor_register: + This function creates a new sensor directory under /sys/class/thermal/ + as sensor[0-*]. This API is expected to be called by thermal sensor + drivers. These drivers may or may not be in thermal subsystem. This + function returns a thermal_sensor structure on success and appropriate + error on failure. + + name: Name of the sensor + count: Number of programmable thresholds associated with this sensor + devdata: Device private data + ops: Thermal sensor callbacks + .get_temp: obtain the current temperature of the sensor + .get_trend: obtain the trend of the sensor + .get_threshold: get a particular threshold temperature + .set_threshold: set a particular threshold temperature + .get_hyst: get hysteresis value associated with a threshold + .set_hyst: set hysteresis value associated with a threshold + +2.1.2 thermal_sensor_unregister: + This function deletes the sensor directory under /sys/class/thermal/ + for the given sensor. Thermal sensor drivers may call this API + during the driver's 'exit' routine. + + ts: Thermal sensor that has to be unregistered + +2.1.3 enable_sensor_thresholds: + This function creates 'threshold[0-*]' attributes under a particular + sensorX directory. These values are RW. This function is called by + the sensr driver only if the sensor supports interrupt mechanism. + + ts: Thermal sensor for which thresholds have to be enabled + num_thresholds: Number of thresholds supported by the sensor + +2.2: For Cooling Devices +2.2.1 thermal_cooling_device_register: + This function adds a new thermal cooling device (fan/processor/...) + to /sys/class/thermal/ folder as cooling_device[0-*]. This function + is expected to be called by cooling device drivers that may be + present in other subsystems also. + + name: the cooling device name + devdata: device private data + ops: thermal cooling devices callbacks + .get_max_state: get the Maximum throttle state of the cooling device + .get_cur_state: get the Current throttle state of the cooling device + .set_cur_state: set the Current throttle state of the cooling device + +2.2.2 thermal_cooling_device_unregister: + This function deletes the given cdev entry form /sys/class/thermal; + and also cleans all the symlinks referred from various zones. + + cdev: Cooling device to be unregistered + +2.3: For Thermal Zones +2.3.1 create_thermal_zone: + This function adds a new 'zone' under /sys/class/thermal/ + directory as zone[0-*]. This zone has at least one thermal + sensor and at most MAX_SENSORS_PER_ZONE number of sensors + attached to it. Similarly, this zone has at least one cdev + and at most MAX_CDEVS_PER_ZONE number of cdevs attached to it. + Both the MAX_*_PER_ZONE values are configurable, through + Kconfig option(during 'menuconfig'). + + name: Name of the thermal zone + devdata: Device private data + +2.3.2 add_sensor_to_zone + This function adds a 'sensorX' entry under /sys/class/thermal/ + zoneY/ directory. This 'sensorX' is a symlink to the actual + sensor entry under /sys/class/thermal/. Correspondingly, the + method remove_sensor_from_zone deletes the symlink. + + tz: thermal zone structure + ts: thermal sensor structure + +2.3.3 add_cdev_to_zone + This function adds a 'cdevX' entry under /sys/class/thermal/ + zoneY/ directory. This 'cdevX' is a symlink to the actual + cdev entry under /sys/class/thermal/. Correspondingly, the + method remove_cdev_from_zone deletes the symlink. + + tz: thermal zone structure + cdev: thermal cooling device structure + +2.4 For Thermal Trip +2.4.1 add_sensor_trip_info + This function adds trip point information for the given sensor, + (under a given zone) under /sys/class/thermal/zoneX/thermal_trip/ + This API creates 4 sysfs attributes namely active, passive, hot, + and critical. Each of these hold one or more trip point temperature + values, as provided from platform data. + + tz: thermal zone structure + ts: thermal sensor to which the trip points are attached + trip: trip point structure. Usually obtained from platform data + +2.5 For Thermal Map +2.5.1 add_map_entry + This function adds a 'map[0-*]' sysfs attribute under + /sys/class/thermal/zoneX/thermal_map/. Each map holds a space + separated list of values, that specify the binding relationship + between a sensor and a cdev in the given zone. The map structure + is typically obtained as platform data. For example, through + ACPI tables, SFI tables, Device tree etc. + + tz: thermal zone to which a 'map' is being added + map: thermal_map structure + +3. Sysfs attributes structure +----------------------------- +Thermal sysfs attributes will be represented under /sys/class/thermal. + +3.1: For Thermal Sensors + /sys/class/thermal/sensor[0-*]: + |---type: Name of the thermal sensor + |---temp_input: Current temperature in mC + |---threshold[0-*]: Threshold temperature in mC + |---threshold[0-*]_hyst:Optional hysteresis value in mC + +3.2: For Thermal Cooling Devices + /sys/class/thermal/cooling_device[0-*]: + |---type: Type of the cooling device + |---max_state: Maximum throttle state of the cdev + |---cur_state: Current throttle state of the cdev + +3.3: For Thermal Zones + /sys/class/thermal/zone[0-*]: + |---name: Name of the thermal + |---sensorX: Symlink to ../sensorX + |---cdevY: Symlink to ../cdevY + |---thermal_trip: trip point values for sensors + |---thermal_map: mapping info between sensors and cdevs + +3.4: For Thermal Trip + This attribute represents the trip point values for all sensors + present in the thermal zone. All values are in mC. + /sys/class/thermal/zoneX/thermal_trip/sensorY: + |---hot: hot trip point value + |---critical: critical trip point value + |---passive: list of passive trip point values + |---active: list of active trip point values + +3.5: For Thermal Map + Each attribute represents the mapping/binding information between + a sensor and a cdev, together with a trip type. + /sys/class/thermal/zoneX/thermal_map/: + |---mapX: mapping information + A typical map entry is like below: + + trip_type sensor cdev trip_mask weight(s) + passive cpu proc 0x03 50 30 + active cpu fan0 0x03 50 70 + + The trip mask is a bit string; if 'n' th bit is set, then for + trip point 'n' this cdev is throttled with the given weight[n].