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| -rw-r--r-- | Documentation/driver-api/thermal/cpu-cooling-api.rst | 107 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/cpu-idle-cooling.rst | 199 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/exynos_thermal.rst | 90 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/exynos_thermal_emulation.rst | 61 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/index.rst | 19 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/intel_powerclamp.rst | 320 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/nouveau_thermal.rst | 96 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/power_allocator.rst | 271 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/sysfs-api.rst | 784 | ||||
| -rw-r--r-- | Documentation/driver-api/thermal/x86_pkg_temperature_thermal.rst | 55 |
10 files changed, 2002 insertions, 0 deletions
diff --git a/Documentation/driver-api/thermal/cpu-cooling-api.rst b/Documentation/driver-api/thermal/cpu-cooling-api.rst new file mode 100644 index 000000000..645d914c4 --- /dev/null +++ b/Documentation/driver-api/thermal/cpu-cooling-api.rst @@ -0,0 +1,107 @@ +======================= +CPU cooling APIs How To +======================= + +Written by Amit Daniel Kachhap <amit.kachhap@linaro.org> + +Updated: 6 Jan 2015 + +Copyright (c) 2012 Samsung Electronics Co., Ltd(http://www.samsung.com) + +0. Introduction +=============== + +The generic cpu cooling(freq clipping) provides registration/unregistration APIs +to the caller. The binding of the cooling devices to the trip point is left for +the user. The registration APIs returns the cooling device pointer. + +1. cpu cooling APIs +=================== + +1.1 cpufreq registration/unregistration APIs +-------------------------------------------- + + :: + + struct thermal_cooling_device + *cpufreq_cooling_register(struct cpumask *clip_cpus) + + This interface function registers the cpufreq cooling device with the name + "thermal-cpufreq-%x". This api can support multiple instances of cpufreq + cooling devices. + + clip_cpus: + cpumask of cpus where the frequency constraints will happen. + + :: + + struct thermal_cooling_device + *of_cpufreq_cooling_register(struct cpufreq_policy *policy) + + This interface function registers the cpufreq cooling device with + the name "thermal-cpufreq-%x" linking it with a device tree node, in + order to bind it via the thermal DT code. This api can support multiple + instances of cpufreq cooling devices. + + policy: + CPUFreq policy. + + + :: + + void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) + + This interface function unregisters the "thermal-cpufreq-%x" cooling device. + + cdev: Cooling device pointer which has to be unregistered. + +2. Power models +=============== + +The power API registration functions provide a simple power model for +CPUs. The current power is calculated as dynamic power (static power isn't +supported currently). This power model requires that the operating-points of +the CPUs are registered using the kernel's opp library and the +`cpufreq_frequency_table` is assigned to the `struct device` of the +cpu. If you are using CONFIG_CPUFREQ_DT then the +`cpufreq_frequency_table` should already be assigned to the cpu +device. + +The dynamic power consumption of a processor depends on many factors. +For a given processor implementation the primary factors are: + +- The time the processor spends running, consuming dynamic power, as + compared to the time in idle states where dynamic consumption is + negligible. Herein we refer to this as 'utilisation'. +- The voltage and frequency levels as a result of DVFS. The DVFS + level is a dominant factor governing power consumption. +- In running time the 'execution' behaviour (instruction types, memory + access patterns and so forth) causes, in most cases, a second order + variation. In pathological cases this variation can be significant, + but typically it is of a much lesser impact than the factors above. + +A high level dynamic power consumption model may then be represented as:: + + Pdyn = f(run) * Voltage^2 * Frequency * Utilisation + +f(run) here represents the described execution behaviour and its +result has a units of Watts/Hz/Volt^2 (this often expressed in +mW/MHz/uVolt^2) + +The detailed behaviour for f(run) could be modelled on-line. However, +in practice, such an on-line model has dependencies on a number of +implementation specific processor support and characterisation +factors. Therefore, in initial implementation that contribution is +represented as a constant coefficient. This is a simplification +consistent with the relative contribution to overall power variation. + +In this simplified representation our model becomes:: + + Pdyn = Capacitance * Voltage^2 * Frequency * Utilisation + +Where `capacitance` is a constant that represents an indicative +running time dynamic power coefficient in fundamental units of +mW/MHz/uVolt^2. Typical values for mobile CPUs might lie in range +from 100 to 500. For reference, the approximate values for the SoC in +ARM's Juno Development Platform are 530 for the Cortex-A57 cluster and +140 for the Cortex-A53 cluster. diff --git a/Documentation/driver-api/thermal/cpu-idle-cooling.rst b/Documentation/driver-api/thermal/cpu-idle-cooling.rst new file mode 100644 index 000000000..c2a7ca676 --- /dev/null +++ b/Documentation/driver-api/thermal/cpu-idle-cooling.rst @@ -0,0 +1,199 @@ +.. SPDX-License-Identifier: GPL-2.0 + +================ +CPU Idle Cooling +================ + +Situation: +---------- + +Under certain circumstances a SoC can reach a critical temperature +limit and is unable to stabilize the temperature around a temperature +control. When the SoC has to stabilize the temperature, the kernel can +act on a cooling device to mitigate the dissipated power. When the +critical temperature is reached, a decision must be taken to reduce +the temperature, that, in turn impacts performance. + +Another situation is when the silicon temperature continues to +increase even after the dynamic leakage is reduced to its minimum by +clock gating the component. This runaway phenomenon can continue due +to the static leakage. The only solution is to power down the +component, thus dropping the dynamic and static leakage that will +allow the component to cool down. + +Last but not least, the system can ask for a specific power budget but +because of the OPP density, we can only choose an OPP with a power +budget lower than the requested one and under-utilize the CPU, thus +losing performance. In other words, one OPP under-utilizes the CPU +with a power less than the requested power budget and the next OPP +exceeds the power budget. An intermediate OPP could have been used if +it were present. + +Solutions: +---------- + +If we can remove the static and the dynamic leakage for a specific +duration in a controlled period, the SoC temperature will +decrease. Acting on the idle state duration or the idle cycle +injection period, we can mitigate the temperature by modulating the +power budget. + +The Operating Performance Point (OPP) density has a great influence on +the control precision of cpufreq, however different vendors have a +plethora of OPP density, and some have large power gap between OPPs, +that will result in loss of performance during thermal control and +loss of power in other scenarios. + +At a specific OPP, we can assume that injecting idle cycle on all CPUs +belong to the same cluster, with a duration greater than the cluster +idle state target residency, we lead to dropping the static and the +dynamic leakage for this period (modulo the energy needed to enter +this state). So the sustainable power with idle cycles has a linear +relation with the OPP’s sustainable power and can be computed with a +coefficient similar to:: + + Power(IdleCycle) = Coef x Power(OPP) + +Idle Injection: +--------------- + +The base concept of the idle injection is to force the CPU to go to an +idle state for a specified time each control cycle, it provides +another way to control CPU power and heat in addition to +cpufreq. Ideally, if all CPUs belonging to the same cluster, inject +their idle cycles synchronously, the cluster can reach its power down +state with a minimum power consumption and reduce the static leakage +to almost zero. However, these idle cycles injection will add extra +latencies as the CPUs will have to wakeup from a deep sleep state. + +We use a fixed duration of idle injection that gives an acceptable +performance penalty and a fixed latency. Mitigation can be increased +or decreased by modulating the duty cycle of the idle injection. + +:: + + ^ + | + | + |------- ------- + |_______|_______________________|_______|___________ + + <------> + idle <----------------------> + running + + <-----------------------------> + duty cycle 25% + + +The implementation of the cooling device bases the number of states on +the duty cycle percentage. When no mitigation is happening the cooling +device state is zero, meaning the duty cycle is 0%. + +When the mitigation begins, depending on the governor's policy, a +starting state is selected. With a fixed idle duration and the duty +cycle (aka the cooling device state), the running duration can be +computed. + +The governor will change the cooling device state thus the duty cycle +and this variation will modulate the cooling effect. + +:: + + ^ + | + | + |------- ------- + |_______|_______________|_______|___________ + + <------> + idle <--------------> + running + + <---------------------> + duty cycle 33% + + + ^ + | + | + |------- ------- + |_______|_______|_______|___________ + + <------> + idle <------> + running + + <-------------> + duty cycle 50% + +The idle injection duration value must comply with the constraints: + +- It is less than or equal to the latency we tolerate when the + mitigation begins. It is platform dependent and will depend on the + user experience, reactivity vs performance trade off we want. This + value should be specified. + +- It is greater than the idle state’s target residency we want to go + for thermal mitigation, otherwise we end up consuming more energy. + +Power considerations +-------------------- + +When we reach the thermal trip point, we have to sustain a specified +power for a specific temperature but at this time we consume:: + + Power = Capacitance x Voltage^2 x Frequency x Utilisation + +... which is more than the sustainable power (or there is something +wrong in the system setup). The ‘Capacitance’ and ‘Utilisation’ are a +fixed value, ‘Voltage’ and the ‘Frequency’ are fixed artificially +because we don’t want to change the OPP. We can group the +‘Capacitance’ and the ‘Utilisation’ into a single term which is the +‘Dynamic Power Coefficient (Cdyn)’ Simplifying the above, we have:: + + Pdyn = Cdyn x Voltage^2 x Frequency + +The power allocator governor will ask us somehow to reduce our power +in order to target the sustainable power defined in the device +tree. So with the idle injection mechanism, we want an average power +(Ptarget) resulting in an amount of time running at full power on a +specific OPP and idle another amount of time. That could be put in a +equation:: + + P(opp)target = ((Trunning x (P(opp)running) + (Tidle x P(opp)idle)) / + (Trunning + Tidle) + + ... + + Tidle = Trunning x ((P(opp)running / P(opp)target) - 1) + +At this point if we know the running period for the CPU, that gives us +the idle injection we need. Alternatively if we have the idle +injection duration, we can compute the running duration with:: + + Trunning = Tidle / ((P(opp)running / P(opp)target) - 1) + +Practically, if the running power is less than the targeted power, we +end up with a negative time value, so obviously the equation usage is +bound to a power reduction, hence a higher OPP is needed to have the +running power greater than the targeted power. + +However, in this demonstration we ignore three aspects: + + * The static leakage is not defined here, we can introduce it in the + equation but assuming it will be zero most of the time as it is + difficult to get the values from the SoC vendors + + * The idle state wake up latency (or entry + exit latency) is not + taken into account, it must be added in the equation in order to + rigorously compute the idle injection + + * The injected idle duration must be greater than the idle state + target residency, otherwise we end up consuming more energy and + potentially invert the mitigation effect + +So the final equation is:: + + Trunning = (Tidle - Twakeup ) x + (((P(opp)dyn + P(opp)static ) - P(opp)target) / P(opp)target ) diff --git a/Documentation/driver-api/thermal/exynos_thermal.rst b/Documentation/driver-api/thermal/exynos_thermal.rst new file mode 100644 index 000000000..764df4ab5 --- /dev/null +++ b/Documentation/driver-api/thermal/exynos_thermal.rst @@ -0,0 +1,90 @@ +======================== +Kernel driver exynos_tmu +======================== + +Supported chips: + +* ARM Samsung Exynos4, Exynos5 series of SoC + + Datasheet: Not publicly available + +Authors: Donggeun Kim <dg77.kim@samsung.com> +Authors: Amit Daniel <amit.daniel@samsung.com> + +TMU controller Description: +--------------------------- + +This driver allows to read temperature inside Samsung Exynos4/5 series of SoC. + +The chip only exposes the measured 8-bit temperature code value +through a register. +Temperature can be taken from the temperature code. +There are three equations converting from temperature to temperature code. + +The three equations are: + 1. Two point trimming:: + + Tc = (T - 25) * (TI2 - TI1) / (85 - 25) + TI1 + + 2. One point trimming:: + + Tc = T + TI1 - 25 + + 3. No trimming:: + + Tc = T + 50 + + Tc: + Temperature code, T: Temperature, + TI1: + Trimming info for 25 degree Celsius (stored at TRIMINFO register) + Temperature code measured at 25 degree Celsius which is unchanged + TI2: + Trimming info for 85 degree Celsius (stored at TRIMINFO register) + Temperature code measured at 85 degree Celsius which is unchanged + +TMU(Thermal Management Unit) in Exynos4/5 generates interrupt +when temperature exceeds pre-defined levels. +The maximum number of configurable threshold is five. +The threshold levels are defined as follows:: + + Level_0: current temperature > trigger_level_0 + threshold + Level_1: current temperature > trigger_level_1 + threshold + Level_2: current temperature > trigger_level_2 + threshold + Level_3: current temperature > trigger_level_3 + threshold + +The threshold and each trigger_level are set +through the corresponding registers. + +When an interrupt occurs, this driver notify kernel thermal framework +with the function exynos_report_trigger. +Although an interrupt condition for level_0 can be set, +it can be used to synchronize the cooling action. + +TMU driver description: +----------------------- + +The exynos thermal driver is structured as:: + + Kernel Core thermal framework + (thermal_core.c, step_wise.c, cpufreq_cooling.c) + ^ + | + | + TMU configuration data -----> TMU Driver <----> Exynos Core thermal wrapper + (exynos_tmu_data.c) (exynos_tmu.c) (exynos_thermal_common.c) + (exynos_tmu_data.h) (exynos_tmu.h) (exynos_thermal_common.h) + +a) TMU configuration data: + This consist of TMU register offsets/bitfields + described through structure exynos_tmu_registers. Also several + other platform data (struct exynos_tmu_platform_data) members + are used to configure the TMU. +b) TMU driver: + This component initialises the TMU controller and sets different + thresholds. It invokes core thermal implementation with the call + exynos_report_trigger. +c) Exynos Core thermal wrapper: + This provides 3 wrapper function to use the + Kernel core thermal framework. They are exynos_unregister_thermal, + exynos_register_thermal and exynos_report_trigger. diff --git a/Documentation/driver-api/thermal/exynos_thermal_emulation.rst b/Documentation/driver-api/thermal/exynos_thermal_emulation.rst new file mode 100644 index 000000000..c21d10838 --- /dev/null +++ b/Documentation/driver-api/thermal/exynos_thermal_emulation.rst @@ -0,0 +1,61 @@ +===================== +Exynos Emulation Mode +===================== + +Copyright (C) 2012 Samsung Electronics + +Written by Jonghwa Lee <jonghwa3.lee@samsung.com> + +Description +----------- + +Exynos 4x12 (4212, 4412) and 5 series provide emulation mode for thermal +management unit. Thermal emulation mode supports software debug for +TMU's operation. User can set temperature manually with software code +and TMU will read current temperature from user value not from sensor's +value. + +Enabling CONFIG_THERMAL_EMULATION option will make this support +available. When it's enabled, sysfs node will be created as +/sys/devices/virtual/thermal/thermal_zone'zone id'/emul_temp. + +The sysfs node, 'emul_node', will contain value 0 for the initial state. +When you input any temperature you want to update to sysfs node, it +automatically enable emulation mode and current temperature will be +changed into it. + +(Exynos also supports user changeable delay time which would be used to +delay of changing temperature. However, this node only uses same delay +of real sensing time, 938us.) + +Exynos emulation mode requires synchronous of value changing and +enabling. It means when you want to update the any value of delay or +next temperature, then you have to enable emulation mode at the same +time. (Or you have to keep the mode enabling.) If you don't, it fails to +change the value to updated one and just use last succeessful value +repeatedly. That's why this node gives users the right to change +termerpature only. Just one interface makes it more simply to use. + +Disabling emulation mode only requires writing value 0 to sysfs node. + +:: + + + TEMP 120 | + | + 100 | + | + 80 | + | +----------- + 60 | | | + | +-------------| | + 40 | | | | + | | | | + 20 | | | +---------- + | | | | | + 0 |______________|_____________|__________|__________|_________ + A A A A TIME + |<----->| |<----->| |<----->| | + | 938us | | | | | | + emulation : 0 50 | 70 | 20 | 0 + current temp: sensor 50 70 20 sensor diff --git a/Documentation/driver-api/thermal/index.rst b/Documentation/driver-api/thermal/index.rst new file mode 100644 index 000000000..4cb0b9b6b --- /dev/null +++ b/Documentation/driver-api/thermal/index.rst @@ -0,0 +1,19 @@ +.. SPDX-License-Identifier: GPL-2.0 + +======= +Thermal +======= + +.. toctree:: + :maxdepth: 1 + + cpu-cooling-api + cpu-idle-cooling + sysfs-api + power_allocator + + exynos_thermal + exynos_thermal_emulation + intel_powerclamp + nouveau_thermal + x86_pkg_temperature_thermal diff --git a/Documentation/driver-api/thermal/intel_powerclamp.rst b/Documentation/driver-api/thermal/intel_powerclamp.rst new file mode 100644 index 000000000..3f6dfb0b3 --- /dev/null +++ b/Documentation/driver-api/thermal/intel_powerclamp.rst @@ -0,0 +1,320 @@ +======================= +Intel Powerclamp Driver +======================= + +By: + - Arjan van de Ven <arjan@linux.intel.com> + - Jacob Pan <jacob.jun.pan@linux.intel.com> + +.. Contents: + + (*) Introduction + - Goals and Objectives + + (*) Theory of Operation + - Idle Injection + - Calibration + + (*) Performance Analysis + - Effectiveness and Limitations + - Power vs Performance + - Scalability + - Calibration + - Comparison with Alternative Techniques + + (*) Usage and Interfaces + - Generic Thermal Layer (sysfs) + - Kernel APIs (TBD) + +INTRODUCTION +============ + +Consider the situation where a system’s power consumption must be +reduced at runtime, due to power budget, thermal constraint, or noise +level, and where active cooling is not preferred. Software managed +passive power reduction must be performed to prevent the hardware +actions that are designed for catastrophic scenarios. + +Currently, P-states, T-states (clock modulation), and CPU offlining +are used for CPU throttling. + +On Intel CPUs, C-states provide effective power reduction, but so far +they’re only used opportunistically, based on workload. With the +development of intel_powerclamp driver, the method of synchronizing +idle injection across all online CPU threads was introduced. The goal +is to achieve forced and controllable C-state residency. + +Test/Analysis has been made in the areas of power, performance, +scalability, and user experience. In many cases, clear advantage is +shown over taking the CPU offline or modulating the CPU clock. + + +THEORY OF OPERATION +=================== + +Idle Injection +-------------- + +On modern Intel processors (Nehalem or later), package level C-state +residency is available in MSRs, thus also available to the kernel. + +These MSRs are:: + + #define MSR_PKG_C2_RESIDENCY 0x60D + #define MSR_PKG_C3_RESIDENCY 0x3F8 + #define MSR_PKG_C6_RESIDENCY 0x3F9 + #define MSR_PKG_C7_RESIDENCY 0x3FA + +If the kernel can also inject idle time to the system, then a +closed-loop control system can be established that manages package +level C-state. The intel_powerclamp driver is conceived as such a +control system, where the target set point is a user-selected idle +ratio (based on power reduction), and the error is the difference +between the actual package level C-state residency ratio and the target idle +ratio. + +Injection is controlled by high priority kernel threads, spawned for +each online CPU. + +These kernel threads, with SCHED_FIFO class, are created to perform +clamping actions of controlled duty ratio and duration. Each per-CPU +thread synchronizes its idle time and duration, based on the rounding +of jiffies, so accumulated errors can be prevented to avoid a jittery +effect. Threads are also bound to the CPU such that they cannot be +migrated, unless the CPU is taken offline. In this case, threads +belong to the offlined CPUs will be terminated immediately. + +Running as SCHED_FIFO and relatively high priority, also allows such +scheme to work for both preemptable and non-preemptable kernels. +Alignment of idle time around jiffies ensures scalability for HZ +values. This effect can be better visualized using a Perf timechart. +The following diagram shows the behavior of kernel thread +kidle_inject/cpu. During idle injection, it runs monitor/mwait idle +for a given "duration", then relinquishes the CPU to other tasks, +until the next time interval. + +The NOHZ schedule tick is disabled during idle time, but interrupts +are not masked. Tests show that the extra wakeups from scheduler tick +have a dramatic impact on the effectiveness of the powerclamp driver +on large scale systems (Westmere system with 80 processors). + +:: + + CPU0 + ____________ ____________ + kidle_inject/0 | sleep | mwait | sleep | + _________| |________| |_______ + duration + CPU1 + ____________ ____________ + kidle_inject/1 | sleep | mwait | sleep | + _________| |________| |_______ + ^ + | + | + roundup(jiffies, interval) + +Only one CPU is allowed to collect statistics and update global +control parameters. This CPU is referred to as the controlling CPU in +this document. The controlling CPU is elected at runtime, with a +policy that favors BSP, taking into account the possibility of a CPU +hot-plug. + +In terms of dynamics of the idle control system, package level idle +time is considered largely as a non-causal system where its behavior +cannot be based on the past or current input. Therefore, the +intel_powerclamp driver attempts to enforce the desired idle time +instantly as given input (target idle ratio). After injection, +powerclamp monitors the actual idle for a given time window and adjust +the next injection accordingly to avoid over/under correction. + +When used in a causal control system, such as a temperature control, +it is up to the user of this driver to implement algorithms where +past samples and outputs are included in the feedback. For example, a +PID-based thermal controller can use the powerclamp driver to +maintain a desired target temperature, based on integral and +derivative gains of the past samples. + + + +Calibration +----------- +During scalability testing, it is observed that synchronized actions +among CPUs become challenging as the number of cores grows. This is +also true for the ability of a system to enter package level C-states. + +To make sure the intel_powerclamp driver scales well, online +calibration is implemented. The goals for doing such a calibration +are: + +a) determine the effective range of idle injection ratio +b) determine the amount of compensation needed at each target ratio + +Compensation to each target ratio consists of two parts: + + a) steady state error compensation + This is to offset the error occurring when the system can + enter idle without extra wakeups (such as external interrupts). + + b) dynamic error compensation + When an excessive amount of wakeups occurs during idle, an + additional idle ratio can be added to quiet interrupts, by + slowing down CPU activities. + +A debugfs file is provided for the user to examine compensation +progress and results, such as on a Westmere system:: + + [jacob@nex01 ~]$ cat + /sys/kernel/debug/intel_powerclamp/powerclamp_calib + controlling cpu: 0 + pct confidence steady dynamic (compensation) + 0 0 0 0 + 1 1 0 0 + 2 1 1 0 + 3 3 1 0 + 4 3 1 0 + 5 3 1 0 + 6 3 1 0 + 7 3 1 0 + 8 3 1 0 + ... + 30 3 2 0 + 31 3 2 0 + 32 3 1 0 + 33 3 2 0 + 34 3 1 0 + 35 3 2 0 + 36 3 1 0 + 37 3 2 0 + 38 3 1 0 + 39 3 2 0 + 40 3 3 0 + 41 3 1 0 + 42 3 2 0 + 43 3 1 0 + 44 3 1 0 + 45 3 2 0 + 46 3 3 0 + 47 3 0 0 + 48 3 2 0 + 49 3 3 0 + +Calibration occurs during runtime. No offline method is available. +Steady state compensation is used only when confidence levels of all +adjacent ratios have reached satisfactory level. A confidence level +is accumulated based on clean data collected at runtime. Data +collected during a period without extra interrupts is considered +clean. + +To compensate for excessive amounts of wakeup during idle, additional +idle time is injected when such a condition is detected. Currently, +we have a simple algorithm to double the injection ratio. A possible +enhancement might be to throttle the offending IRQ, such as delaying +EOI for level triggered interrupts. But it is a challenge to be +non-intrusive to the scheduler or the IRQ core code. + + +CPU Online/Offline +------------------ +Per-CPU kernel threads are started/stopped upon receiving +notifications of CPU hotplug activities. The intel_powerclamp driver +keeps track of clamping kernel threads, even after they are migrated +to other CPUs, after a CPU offline event. + + +Performance Analysis +==================== +This section describes the general performance data collected on +multiple systems, including Westmere (80P) and Ivy Bridge (4P, 8P). + +Effectiveness and Limitations +----------------------------- +The maximum range that idle injection is allowed is capped at 50 +percent. As mentioned earlier, since interrupts are allowed during +forced idle time, excessive interrupts could result in less +effectiveness. The extreme case would be doing a ping -f to generated +flooded network interrupts without much CPU acknowledgement. In this +case, little can be done from the idle injection threads. In most +normal cases, such as scp a large file, applications can be throttled +by the powerclamp driver, since slowing down the CPU also slows down +network protocol processing, which in turn reduces interrupts. + +When control parameters change at runtime by the controlling CPU, it +may take an additional period for the rest of the CPUs to catch up +with the changes. During this time, idle injection is out of sync, +thus not able to enter package C- states at the expected ratio. But +this effect is minor, in that in most cases change to the target +ratio is updated much less frequently than the idle injection +frequency. + +Scalability +----------- +Tests also show a minor, but measurable, difference between the 4P/8P +Ivy Bridge system and the 80P Westmere server under 50% idle ratio. +More compensation is needed on Westmere for the same amount of +target idle ratio. The compensation also increases as the idle ratio +gets larger. The above reason constitutes the need for the +calibration code. + +On the IVB 8P system, compared to an offline CPU, powerclamp can +achieve up to 40% better performance per watt. (measured by a spin +counter summed over per CPU counting threads spawned for all running +CPUs). + +Usage and Interfaces +==================== +The powerclamp driver is registered to the generic thermal layer as a +cooling device. Currently, it’s not bound to any thermal zones:: + + jacob@chromoly:/sys/class/thermal/cooling_device14$ grep . * + cur_state:0 + max_state:50 + type:intel_powerclamp + +cur_state allows user to set the desired idle percentage. Writing 0 to +cur_state will stop idle injection. Writing a value between 1 and +max_state will start the idle injection. Reading cur_state returns the +actual and current idle percentage. This may not be the same value +set by the user in that current idle percentage depends on workload +and includes natural idle. When idle injection is disabled, reading +cur_state returns value -1 instead of 0 which is to avoid confusing +100% busy state with the disabled state. + +Example usage: +- To inject 25% idle time:: + + $ sudo sh -c "echo 25 > /sys/class/thermal/cooling_device80/cur_state + +If the system is not busy and has more than 25% idle time already, +then the powerclamp driver will not start idle injection. Using Top +will not show idle injection kernel threads. + +If the system is busy (spin test below) and has less than 25% natural +idle time, powerclamp kernel threads will do idle injection. Forced +idle time is accounted as normal idle in that common code path is +taken as the idle task. + +In this example, 24.1% idle is shown. This helps the system admin or +user determine the cause of slowdown, when a powerclamp driver is in action:: + + + Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie + Cpu(s): 71.2%us, 4.7%sy, 0.0%ni, 24.1%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st + Mem: 3943228k total, 1689632k used, 2253596k free, 74960k buffers + Swap: 4087804k total, 0k used, 4087804k free, 945336k cached + + PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND + 3352 jacob 20 0 262m 644 428 S 286 0.0 0:17.16 spin + 3341 root -51 0 0 0 0 D 25 0.0 0:01.62 kidle_inject/0 + 3344 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/3 + 3342 root -51 0 0 0 0 D 25 0.0 0:01.61 kidle_inject/1 + 3343 root -51 0 0 0 0 D 25 0.0 0:01.60 kidle_inject/2 + 2935 jacob 20 0 696m 125m 35m S 5 3.3 0:31.11 firefox + 1546 root 20 0 158m 20m 6640 S 3 0.5 0:26.97 Xorg + 2100 jacob 20 0 1223m 88m 30m S 3 2.3 0:23.68 compiz + +Tests have shown that by using the powerclamp driver as a cooling +device, a PID based userspace thermal controller can manage to +control CPU temperature effectively, when no other thermal influence +is added. For example, a UltraBook user can compile the kernel under +certain temperature (below most active trip points). diff --git a/Documentation/driver-api/thermal/nouveau_thermal.rst b/Documentation/driver-api/thermal/nouveau_thermal.rst new file mode 100644 index 000000000..79ece266c --- /dev/null +++ b/Documentation/driver-api/thermal/nouveau_thermal.rst @@ -0,0 +1,96 @@ +===================== +Kernel driver nouveau +===================== + +Supported chips: + +* NV43+ + +Authors: Martin Peres (mupuf) <martin.peres@free.fr> + +Description +----------- + +This driver allows to read the GPU core temperature, drive the GPU fan and +set temperature alarms. + +Currently, due to the absence of in-kernel API to access HWMON drivers, Nouveau +cannot access any of the i2c external monitoring chips it may find. If you +have one of those, temperature and/or fan management through Nouveau's HWMON +interface is likely not to work. This document may then not cover your situation +entirely. + +Temperature management +---------------------- + +Temperature is exposed under as a read-only HWMON attribute temp1_input. + +In order to protect the GPU from overheating, Nouveau supports 4 configurable +temperature thresholds: + + * Fan_boost: + Fan speed is set to 100% when reaching this temperature; + * Downclock: + The GPU will be downclocked to reduce its power dissipation; + * Critical: + The GPU is put on hold to further lower power dissipation; + * Shutdown: + Shut the computer down to protect your GPU. + +WARNING: + Some of these thresholds may not be used by Nouveau depending + on your chipset. + +The default value for these thresholds comes from the GPU's vbios. These +thresholds can be configured thanks to the following HWMON attributes: + + * Fan_boost: temp1_auto_point1_temp and temp1_auto_point1_temp_hyst; + * Downclock: temp1_max and temp1_max_hyst; + * Critical: temp1_crit and temp1_crit_hyst; + * Shutdown: temp1_emergency and temp1_emergency_hyst. + +NOTE: Remember that the values are stored as milli degrees Celsius. Don't forget +to multiply! + +Fan management +-------------- + +Not all cards have a drivable fan. If you do, then the following HWMON +attributes should be available: + + * pwm1_enable: + Current fan management mode (NONE, MANUAL or AUTO); + * pwm1: + Current PWM value (power percentage); + * pwm1_min: + The minimum PWM speed allowed; + * pwm1_max: + The maximum PWM speed allowed (bypassed when hitting Fan_boost); + +You may also have the following attribute: + + * fan1_input: + Speed in RPM of your fan. + +Your fan can be driven in different modes: + + * 0: The fan is left untouched; + * 1: The fan can be driven in manual (use pwm1 to change the speed); + * 2; The fan is driven automatically depending on the temperature. + +NOTE: + Be sure to use the manual mode if you want to drive the fan speed manually + +NOTE2: + When operating in manual mode outside the vbios-defined + [PWM_min, PWM_max] range, the reported fan speed (RPM) may not be accurate + depending on your hardware. + +Bug reports +----------- + +Thermal management on Nouveau is new and may not work on all cards. If you have +inquiries, please ping mupuf on IRC (#nouveau, freenode). + +Bug reports should be filled on Freedesktop's bug tracker. Please follow +https://nouveau.freedesktop.org/wiki/Bugs diff --git a/Documentation/driver-api/thermal/power_allocator.rst b/Documentation/driver-api/thermal/power_allocator.rst new file mode 100644 index 000000000..67b6a3297 --- /dev/null +++ b/Documentation/driver-api/thermal/power_allocator.rst @@ -0,0 +1,271 @@ +================================= +Power allocator governor tunables +================================= + +Trip points +----------- + +The governor works optimally with the following two passive trip points: + +1. "switch on" trip point: temperature above which the governor + control loop starts operating. This is the first passive trip + point of the thermal zone. + +2. "desired temperature" trip point: it should be higher than the + "switch on" trip point. This the target temperature the governor + is controlling for. This is the last passive trip point of the + thermal zone. + +PID Controller +-------------- + +The power allocator governor implements a +Proportional-Integral-Derivative controller (PID controller) with +temperature as the control input and power as the controlled output: + + P_max = k_p * e + k_i * err_integral + k_d * diff_err + sustainable_power + +where + - e = desired_temperature - current_temperature + - err_integral is the sum of previous errors + - diff_err = e - previous_error + +It is similar to the one depicted below:: + + k_d + | + current_temp | + | v + | +----------+ +---+ + | +----->| diff_err |-->| X |------+ + | | +----------+ +---+ | + | | | tdp actor + | | k_i | | get_requested_power() + | | | | | | | + | | | | | | | ... + v | v v v v v + +---+ | +-------+ +---+ +---+ +---+ +----------+ + | S |-----+----->| sum e |----->| X |--->| S |-->| S |-->|power | + +---+ | +-------+ +---+ +---+ +---+ |allocation| + ^ | ^ +----------+ + | | | | | + | | +---+ | | | + | +------->| X |-------------------+ v v + | +---+ granted performance + desired_temperature ^ + | + | + k_po/k_pu + +Sustainable power +----------------- + +An estimate of the sustainable dissipatable power (in mW) should be +provided while registering the thermal zone. This estimates the +sustained power that can be dissipated at the desired control +temperature. This is the maximum sustained power for allocation at +the desired maximum temperature. The actual sustained power can vary +for a number of reasons. The closed loop controller will take care of +variations such as environmental conditions, and some factors related +to the speed-grade of the silicon. `sustainable_power` is therefore +simply an estimate, and may be tuned to affect the aggressiveness of +the thermal ramp. For reference, the sustainable power of a 4" phone +is typically 2000mW, while on a 10" tablet is around 4500mW (may vary +depending on screen size). + +If you are using device tree, do add it as a property of the +thermal-zone. For example:: + + thermal-zones { + soc_thermal { + polling-delay = <1000>; + polling-delay-passive = <100>; + sustainable-power = <2500>; + ... + +Instead, if the thermal zone is registered from the platform code, pass a +`thermal_zone_params` that has a `sustainable_power`. If no +`thermal_zone_params` were being passed, then something like below +will suffice:: + + static const struct thermal_zone_params tz_params = { + .sustainable_power = 3500, + }; + +and then pass `tz_params` as the 5th parameter to +`thermal_zone_device_register()` + +k_po and k_pu +------------- + +The implementation of the PID controller in the power allocator +thermal governor allows the configuration of two proportional term +constants: `k_po` and `k_pu`. `k_po` is the proportional term +constant during temperature overshoot periods (current temperature is +above "desired temperature" trip point). Conversely, `k_pu` is the +proportional term constant during temperature undershoot periods +(current temperature below "desired temperature" trip point). + +These controls are intended as the primary mechanism for configuring +the permitted thermal "ramp" of the system. For instance, a lower +`k_pu` value will provide a slower ramp, at the cost of capping +available capacity at a low temperature. On the other hand, a high +value of `k_pu` will result in the governor granting very high power +while temperature is low, and may lead to temperature overshooting. + +The default value for `k_pu` is:: + + 2 * sustainable_power / (desired_temperature - switch_on_temp) + +This means that at `switch_on_temp` the output of the controller's +proportional term will be 2 * `sustainable_power`. The default value +for `k_po` is:: + + sustainable_power / (desired_temperature - switch_on_temp) + +Focusing on the proportional and feed forward values of the PID +controller equation we have:: + + P_max = k_p * e + sustainable_power + +The proportional term is proportional to the difference between the +desired temperature and the current one. When the current temperature +is the desired one, then the proportional component is zero and +`P_max` = `sustainable_power`. That is, the system should operate in +thermal equilibrium under constant load. `sustainable_power` is only +an estimate, which is the reason for closed-loop control such as this. + +Expanding `k_pu` we get:: + + P_max = 2 * sustainable_power * (T_set - T) / (T_set - T_on) + + sustainable_power + +where: + + - T_set is the desired temperature + - T is the current temperature + - T_on is the switch on temperature + +When the current temperature is the switch_on temperature, the above +formula becomes:: + + P_max = 2 * sustainable_power * (T_set - T_on) / (T_set - T_on) + + sustainable_power = 2 * sustainable_power + sustainable_power = + 3 * sustainable_power + +Therefore, the proportional term alone linearly decreases power from +3 * `sustainable_power` to `sustainable_power` as the temperature +rises from the switch on temperature to the desired temperature. + +k_i and integral_cutoff +----------------------- + +`k_i` configures the PID loop's integral term constant. This term +allows the PID controller to compensate for long term drift and for +the quantized nature of the output control: cooling devices can't set +the exact power that the governor requests. When the temperature +error is below `integral_cutoff`, errors are accumulated in the +integral term. This term is then multiplied by `k_i` and the result +added to the output of the controller. Typically `k_i` is set low (1 +or 2) and `integral_cutoff` is 0. + +k_d +--- + +`k_d` configures the PID loop's derivative term constant. It's +recommended to leave it as the default: 0. + +Cooling device power API +======================== + +Cooling devices controlled by this governor must supply the additional +"power" API in their `cooling_device_ops`. It consists on three ops: + +1. :: + + int get_requested_power(struct thermal_cooling_device *cdev, + struct thermal_zone_device *tz, u32 *power); + + +@cdev: + The `struct thermal_cooling_device` pointer +@tz: + thermal zone in which we are currently operating +@power: + pointer in which to store the calculated power + +`get_requested_power()` calculates the power requested by the device +in milliwatts and stores it in @power . It should return 0 on +success, -E* on failure. This is currently used by the power +allocator governor to calculate how much power to give to each cooling +device. + +2. :: + + int state2power(struct thermal_cooling_device *cdev, struct + thermal_zone_device *tz, unsigned long state, + u32 *power); + +@cdev: + The `struct thermal_cooling_device` pointer +@tz: + thermal zone in which we are currently operating +@state: + A cooling device state +@power: + pointer in which to store the equivalent power + +Convert cooling device state @state into power consumption in +milliwatts and store it in @power. It should return 0 on success, -E* +on failure. This is currently used by thermal core to calculate the +maximum power that an actor can consume. + +3. :: + + int power2state(struct thermal_cooling_device *cdev, u32 power, + unsigned long *state); + +@cdev: + The `struct thermal_cooling_device` pointer +@power: + power in milliwatts +@state: + pointer in which to store the resulting state + +Calculate a cooling device state that would make the device consume at +most @power mW and store it in @state. It should return 0 on success, +-E* on failure. This is currently used by the thermal core to convert +a given power set by the power allocator governor to a state that the +cooling device can set. It is a function because this conversion may +depend on external factors that may change so this function should the +best conversion given "current circumstances". + +Cooling device weights +---------------------- + +Weights are a mechanism to bias the allocation among cooling +devices. They express the relative power efficiency of different +cooling devices. Higher weight can be used to express higher power +efficiency. Weighting is relative such that if each cooling device +has a weight of one they are considered equal. This is particularly +useful in heterogeneous systems where two cooling devices may perform +the same kind of compute, but with different efficiency. For example, +a system with two different types of processors. + +If the thermal zone is registered using +`thermal_zone_device_register()` (i.e., platform code), then weights +are passed as part of the thermal zone's `thermal_bind_parameters`. +If the platform is registered using device tree, then they are passed +as the `contribution` property of each map in the `cooling-maps` node. + +Limitations of the power allocator governor +=========================================== + +The power allocator governor's PID controller works best if there is a +periodic tick. If you have a driver that calls +`thermal_zone_device_update()` (or anything that ends up calling the +governor's `throttle()` function) repetitively, the governor response +won't be very good. Note that this is not particular to this +governor, step-wise will also misbehave if you call its throttle() +faster than the normal thermal framework tick (due to interrupts for +example) as it will overreact. diff --git a/Documentation/driver-api/thermal/sysfs-api.rst b/Documentation/driver-api/thermal/sysfs-api.rst new file mode 100644 index 000000000..b40b1f839 --- /dev/null +++ b/Documentation/driver-api/thermal/sysfs-api.rst @@ -0,0 +1,784 @@ +=================================== +Generic Thermal Sysfs driver How To +=================================== + +Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com> + +Updated: 2 January 2008 + +Copyright (c) 2008 Intel Corporation + + +0. Introduction +=============== + +The generic thermal sysfs provides a set of interfaces for thermal zone +devices (sensors) and thermal cooling devices (fan, processor...) to register +with the thermal management solution and to be a part of it. + +This how-to focuses on enabling new thermal zone and cooling devices to +participate in thermal management. +This solution is platform independent and any type of thermal zone devices +and cooling devices should be able to make use of the infrastructure. + +The main task of the thermal sysfs driver is to expose thermal zone attributes +as well as cooling device attributes to the user space. +An intelligent thermal management application can make decisions based on +inputs from thermal zone attributes (the current temperature and trip point +temperature) and throttle appropriate devices. + +- `[0-*]` denotes any positive number starting from 0 +- `[1-*]` denotes any positive number starting from 1 + +1. thermal sysfs driver interface functions +=========================================== + +1.1 thermal zone device interface +--------------------------------- + + :: + + struct thermal_zone_device + *thermal_zone_device_register(char *type, + int trips, int mask, void *devdata, + struct thermal_zone_device_ops *ops, + const struct thermal_zone_params *tzp, + int passive_delay, int polling_delay)) + + This interface function adds a new thermal zone device (sensor) to + /sys/class/thermal folder as `thermal_zone[0-*]`. It tries to bind all the + thermal cooling devices registered at the same time. + + type: + the thermal zone type. + trips: + the total number of trip points this thermal zone supports. + mask: + Bit string: If 'n'th bit is set, then trip point 'n' is writeable. + devdata: + device private data + ops: + thermal zone device call-backs. + + .bind: + bind the thermal zone device with a thermal cooling device. + .unbind: + unbind the thermal zone device with a thermal cooling device. + .get_temp: + get the current temperature of the thermal zone. + .set_trips: + set the trip points window. Whenever the current temperature + is updated, the trip points immediately below and above the + current temperature are found. + .get_mode: + get the current mode (enabled/disabled) of the thermal zone. + + - "enabled" means the kernel thermal management is + enabled. + - "disabled" will prevent kernel thermal driver action + upon trip points so that user applications can take + charge of thermal management. + .set_mode: + set the mode (enabled/disabled) of the thermal zone. + .get_trip_type: + get the type of certain trip point. + .get_trip_temp: + get the temperature above which the certain trip point + will be fired. + .set_emul_temp: + set the emulation temperature which helps in debugging + different threshold temperature points. + tzp: + thermal zone platform parameters. + passive_delay: + number of milliseconds to wait between polls when + performing passive cooling. + polling_delay: + number of milliseconds to wait between polls when checking + whether trip points have been crossed (0 for interrupt driven systems). + + :: + + void thermal_zone_device_unregister(struct thermal_zone_device *tz) + + This interface function removes the thermal zone device. + It deletes the corresponding entry from /sys/class/thermal folder and + unbinds all the thermal cooling devices it uses. + + :: + + struct thermal_zone_device + *thermal_zone_of_sensor_register(struct device *dev, int sensor_id, + void *data, + const struct thermal_zone_of_device_ops *ops) + + This interface adds a new sensor to a DT thermal zone. + This function will search the list of thermal zones described in + device tree and look for the zone that refer to the sensor device + pointed by dev->of_node as temperature providers. For the zone + pointing to the sensor node, the sensor will be added to the DT + thermal zone device. + + The parameters for this interface are: + + dev: + Device node of sensor containing valid node pointer in + dev->of_node. + sensor_id: + a sensor identifier, in case the sensor IP has more + than one sensors + data: + a private pointer (owned by the caller) that will be + passed back, when a temperature reading is needed. + ops: + `struct thermal_zone_of_device_ops *`. + + ============== ======================================= + get_temp a pointer to a function that reads the + sensor temperature. This is mandatory + callback provided by sensor driver. + set_trips a pointer to a function that sets a + temperature window. When this window is + left the driver must inform the thermal + core via thermal_zone_device_update. + get_trend a pointer to a function that reads the + sensor temperature trend. + set_emul_temp a pointer to a function that sets + sensor emulated temperature. + ============== ======================================= + + The thermal zone temperature is provided by the get_temp() function + pointer of thermal_zone_of_device_ops. When called, it will + have the private pointer @data back. + + It returns error pointer if fails otherwise valid thermal zone device + handle. Caller should check the return handle with IS_ERR() for finding + whether success or not. + + :: + + void thermal_zone_of_sensor_unregister(struct device *dev, + struct thermal_zone_device *tzd) + + This interface unregisters a sensor from a DT thermal zone which was + successfully added by interface thermal_zone_of_sensor_register(). + This function removes the sensor callbacks and private data from the + thermal zone device registered with thermal_zone_of_sensor_register() + interface. It will also silent the zone by remove the .get_temp() and + get_trend() thermal zone device callbacks. + + :: + + struct thermal_zone_device + *devm_thermal_zone_of_sensor_register(struct device *dev, + int sensor_id, + void *data, + const struct thermal_zone_of_device_ops *ops) + + This interface is resource managed version of + thermal_zone_of_sensor_register(). + + All details of thermal_zone_of_sensor_register() described in + section 1.1.3 is applicable here. + + The benefit of using this interface to register sensor is that it + is not require to explicitly call thermal_zone_of_sensor_unregister() + in error path or during driver unbinding as this is done by driver + resource manager. + + :: + + void devm_thermal_zone_of_sensor_unregister(struct device *dev, + struct thermal_zone_device *tzd) + + This interface is resource managed version of + thermal_zone_of_sensor_unregister(). + All details of thermal_zone_of_sensor_unregister() described in + section 1.1.4 is applicable here. + Normally this function will not need to be called and the resource + management code will ensure that the resource is freed. + + :: + + int thermal_zone_get_slope(struct thermal_zone_device *tz) + + This interface is used to read the slope attribute value + for the thermal zone device, which might be useful for platform + drivers for temperature calculations. + + :: + + int thermal_zone_get_offset(struct thermal_zone_device *tz) + + This interface is used to read the offset attribute value + for the thermal zone device, which might be useful for platform + drivers for temperature calculations. + +1.2 thermal cooling device interface +------------------------------------ + + + :: + + struct thermal_cooling_device + *thermal_cooling_device_register(char *name, + void *devdata, struct thermal_cooling_device_ops *) + + This interface function adds a new thermal cooling device (fan/processor/...) + to /sys/class/thermal/ folder as `cooling_device[0-*]`. It tries to bind itself + to all the thermal zone devices registered at the same time. + + name: + the cooling device name. + devdata: + device private data. + ops: + thermal cooling devices call-backs. + + .get_max_state: + get the Maximum throttle state of the cooling device. + .get_cur_state: + get the Currently requested throttle state of the + cooling device. + .set_cur_state: + set the Current throttle state of the cooling device. + + :: + + void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) + + This interface function removes the thermal cooling device. + It deletes the corresponding entry from /sys/class/thermal folder and + unbinds itself from all the thermal zone devices using it. + +1.3 interface for binding a thermal zone device with a thermal cooling device +----------------------------------------------------------------------------- + + :: + + int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, + int trip, struct thermal_cooling_device *cdev, + unsigned long upper, unsigned long lower, unsigned int weight); + + This interface function binds a thermal cooling device to a particular trip + point of a thermal zone device. + + This function is usually called in the thermal zone device .bind callback. + + tz: + the thermal zone device + cdev: + thermal cooling device + trip: + indicates which trip point in this thermal zone the cooling device + is associated with. + upper: + the Maximum cooling state for this trip point. + THERMAL_NO_LIMIT means no upper limit, + and the cooling device can be in max_state. + lower: + the Minimum cooling state can be used for this trip point. + THERMAL_NO_LIMIT means no lower limit, + and the cooling device can be in cooling state 0. + weight: + the influence of this cooling device in this thermal + zone. See 1.4.1 below for more information. + + :: + + int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, + int trip, struct thermal_cooling_device *cdev); + + This interface function unbinds a thermal cooling device from a particular + trip point of a thermal zone device. This function is usually called in + the thermal zone device .unbind callback. + + tz: + the thermal zone device + cdev: + thermal cooling device + trip: + indicates which trip point in this thermal zone the cooling device + is associated with. + +1.4 Thermal Zone Parameters +--------------------------- + + :: + + struct thermal_bind_params + + This structure defines the following parameters that are used to bind + a zone with a cooling device for a particular trip point. + + .cdev: + The cooling device pointer + .weight: + The 'influence' of a particular cooling device on this + zone. This is relative to the rest of the cooling + devices. For example, if all cooling devices have a + weight of 1, then they all contribute the same. You can + use percentages if you want, but it's not mandatory. A + weight of 0 means that this cooling device doesn't + contribute to the cooling of this zone unless all cooling + devices have a weight of 0. If all weights are 0, then + they all contribute the same. + .trip_mask: + This is a bit mask that gives the binding relation between + this thermal zone and cdev, for a particular trip point. + If nth bit is set, then the cdev and thermal zone are bound + for trip point n. + .binding_limits: + This is an array of cooling state limits. Must have + exactly 2 * thermal_zone.number_of_trip_points. It is an + array consisting of tuples <lower-state upper-state> of + state limits. Each trip will be associated with one state + limit tuple when binding. A NULL pointer means + <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> on all trips. + These limits are used when binding a cdev to a trip point. + .match: + This call back returns success(0) if the 'tz and cdev' need to + be bound, as per platform data. + + :: + + struct thermal_zone_params + + This structure defines the platform level parameters for a thermal zone. + This data, for each thermal zone should come from the platform layer. + This is an optional feature where some platforms can choose not to + provide this data. + + .governor_name: + Name of the thermal governor used for this zone + .no_hwmon: + a boolean to indicate if the thermal to hwmon sysfs interface + is required. when no_hwmon == false, a hwmon sysfs interface + will be created. when no_hwmon == true, nothing will be done. + In case the thermal_zone_params is NULL, the hwmon interface + will be created (for backward compatibility). + .num_tbps: + Number of thermal_bind_params entries for this zone + .tbp: + thermal_bind_params entries + +2. sysfs attributes structure +============================= + +== ================ +RO read only value +WO write only value +RW read/write value +== ================ + +Thermal sysfs attributes will be represented under /sys/class/thermal. +Hwmon sysfs I/F extension is also available under /sys/class/hwmon +if hwmon is compiled in or built as a module. + +Thermal zone device sys I/F, created once it's registered:: + + /sys/class/thermal/thermal_zone[0-*]: + |---type: Type of the thermal zone + |---temp: Current temperature + |---mode: Working mode of the thermal zone + |---policy: Thermal governor used for this zone + |---available_policies: Available thermal governors for this zone + |---trip_point_[0-*]_temp: Trip point temperature + |---trip_point_[0-*]_type: Trip point type + |---trip_point_[0-*]_hyst: Hysteresis value for this trip point + |---emul_temp: Emulated temperature set node + |---sustainable_power: Sustainable dissipatable power + |---k_po: Proportional term during temperature overshoot + |---k_pu: Proportional term during temperature undershoot + |---k_i: PID's integral term in the power allocator gov + |---k_d: PID's derivative term in the power allocator + |---integral_cutoff: Offset above which errors are accumulated + |---slope: Slope constant applied as linear extrapolation + |---offset: Offset constant applied as linear extrapolation + +Thermal cooling device sys I/F, created once it's registered:: + + /sys/class/thermal/cooling_device[0-*]: + |---type: Type of the cooling device(processor/fan/...) + |---max_state: Maximum cooling state of the cooling device + |---cur_state: Current cooling state of the cooling device + |---stats: Directory containing cooling device's statistics + |---stats/reset: Writing any value resets the statistics + |---stats/time_in_state_ms: Time (msec) spent in various cooling states + |---stats/total_trans: Total number of times cooling state is changed + |---stats/trans_table: Cooing state transition table + + +Then next two dynamic attributes are created/removed in pairs. They represent +the relationship between a thermal zone and its associated cooling device. +They are created/removed for each successful execution of +thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. + +:: + + /sys/class/thermal/thermal_zone[0-*]: + |---cdev[0-*]: [0-*]th cooling device in current thermal zone + |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with + |---cdev[0-*]_weight: Influence of the cooling device in + this thermal zone + +Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, +the generic thermal driver also creates a hwmon sysfs I/F for each _type_ +of thermal zone device. E.g. the generic thermal driver registers one hwmon +class device and build the associated hwmon sysfs I/F for all the registered +ACPI thermal zones. + +:: + + /sys/class/hwmon/hwmon[0-*]: + |---name: The type of the thermal zone devices + |---temp[1-*]_input: The current temperature of thermal zone [1-*] + |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] + +Please read Documentation/hwmon/sysfs-interface.rst for additional information. + +Thermal zone attributes +----------------------- + +type + Strings which represent the thermal zone type. + This is given by thermal zone driver as part of registration. + E.g: "acpitz" indicates it's an ACPI thermal device. + In order to keep it consistent with hwmon sys attribute; this should + be a short, lowercase string, not containing spaces nor dashes. + RO, Required + +temp + Current temperature as reported by thermal zone (sensor). + Unit: millidegree Celsius + RO, Required + +mode + One of the predefined values in [enabled, disabled]. + This file gives information about the algorithm that is currently + managing the thermal zone. It can be either default kernel based + algorithm or user space application. + + enabled + enable Kernel Thermal management. + disabled + Preventing kernel thermal zone driver actions upon + trip points so that user application can take full + charge of the thermal management. + + RW, Optional + +policy + One of the various thermal governors used for a particular zone. + + RW, Required + +available_policies + Available thermal governors which can be used for a particular zone. + + RO, Required + +`trip_point_[0-*]_temp` + The temperature above which trip point will be fired. + + Unit: millidegree Celsius + + RO, Optional + +`trip_point_[0-*]_type` + Strings which indicate the type of the trip point. + + E.g. it can be one of critical, hot, passive, `active[0-*]` for ACPI + thermal zone. + + RO, Optional + +`trip_point_[0-*]_hyst` + The hysteresis value for a trip point, represented as an integer + Unit: Celsius + RW, Optional + +`cdev[0-*]` + Sysfs link to the thermal cooling device node where the sys I/F + for cooling device throttling control represents. + + RO, Optional + +`cdev[0-*]_trip_point` + The trip point in this thermal zone which `cdev[0-*]` is associated + with; -1 means the cooling device is not associated with any trip + point. + + RO, Optional + +`cdev[0-*]_weight` + The influence of `cdev[0-*]` in this thermal zone. This value + is relative to the rest of cooling devices in the thermal + zone. For example, if a cooling device has a weight double + than that of other, it's twice as effective in cooling the + thermal zone. + + RW, Optional + +passive + Attribute is only present for zones in which the passive cooling + policy is not supported by native thermal driver. Default is zero + and can be set to a temperature (in millidegrees) to enable a + passive trip point for the zone. Activation is done by polling with + an interval of 1 second. + + Unit: millidegrees Celsius + + Valid values: 0 (disabled) or greater than 1000 + + RW, Optional + +emul_temp + Interface to set the emulated temperature method in thermal zone + (sensor). After setting this temperature, the thermal zone may pass + this temperature to platform emulation function if registered or + cache it locally. This is useful in debugging different temperature + threshold and its associated cooling action. This is write only node + and writing 0 on this node should disable emulation. + Unit: millidegree Celsius + + WO, Optional + + WARNING: + Be careful while enabling this option on production systems, + because userland can easily disable the thermal policy by simply + flooding this sysfs node with low temperature values. + +sustainable_power + An estimate of the sustained power that can be dissipated by + the thermal zone. Used by the power allocator governor. For + more information see Documentation/driver-api/thermal/power_allocator.rst + + Unit: milliwatts + + RW, Optional + +k_po + The proportional term of the power allocator governor's PID + controller during temperature overshoot. Temperature overshoot + is when the current temperature is above the "desired + temperature" trip point. For more information see + Documentation/driver-api/thermal/power_allocator.rst + + RW, Optional + +k_pu + The proportional term of the power allocator governor's PID + controller during temperature undershoot. Temperature undershoot + is when the current temperature is below the "desired + temperature" trip point. For more information see + Documentation/driver-api/thermal/power_allocator.rst + + RW, Optional + +k_i + The integral term of the power allocator governor's PID + controller. This term allows the PID controller to compensate + for long term drift. For more information see + Documentation/driver-api/thermal/power_allocator.rst + + RW, Optional + +k_d + The derivative term of the power allocator governor's PID + controller. For more information see + Documentation/driver-api/thermal/power_allocator.rst + + RW, Optional + +integral_cutoff + Temperature offset from the desired temperature trip point + above which the integral term of the power allocator + governor's PID controller starts accumulating errors. For + example, if integral_cutoff is 0, then the integral term only + accumulates error when temperature is above the desired + temperature trip point. For more information see + Documentation/driver-api/thermal/power_allocator.rst + + Unit: millidegree Celsius + + RW, Optional + +slope + The slope constant used in a linear extrapolation model + to determine a hotspot temperature based off the sensor's + raw readings. It is up to the device driver to determine + the usage of these values. + + RW, Optional + +offset + The offset constant used in a linear extrapolation model + to determine a hotspot temperature based off the sensor's + raw readings. It is up to the device driver to determine + the usage of these values. + + RW, Optional + +Cooling device attributes +------------------------- + +type + String which represents the type of device, e.g: + + - for generic ACPI: should be "Fan", "Processor" or "LCD" + - for memory controller device on intel_menlow platform: + should be "Memory controller". + + RO, Required + +max_state + The maximum permissible cooling state of this cooling device. + + RO, Required + +cur_state + The current cooling state of this cooling device. + The value can any integer numbers between 0 and max_state: + + - cur_state == 0 means no cooling + - cur_state == max_state means the maximum cooling. + + RW, Required + +stats/reset + Writing any value resets the cooling device's statistics. + WO, Required + +stats/time_in_state_ms: + The amount of time spent by the cooling device in various cooling + states. The output will have "<state> <time>" pair in each line, which + will mean this cooling device spent <time> msec of time at <state>. + Output will have one line for each of the supported states. usertime + units here is 10mS (similar to other time exported in /proc). + RO, Required + + +stats/total_trans: + A single positive value showing the total number of times the state of a + cooling device is changed. + + RO, Required + +stats/trans_table: + This gives fine grained information about all the cooling state + transitions. The cat output here is a two dimensional matrix, where an + entry <i,j> (row i, column j) represents the number of transitions from + State_i to State_j. If the transition table is bigger than PAGE_SIZE, + reading this will return an -EFBIG error. + RO, Required + +3. A simple implementation +========================== + +ACPI thermal zone may support multiple trip points like critical, hot, +passive, active. If an ACPI thermal zone supports critical, passive, +active[0] and active[1] at the same time, it may register itself as a +thermal_zone_device (thermal_zone1) with 4 trip points in all. +It has one processor and one fan, which are both registered as +thermal_cooling_device. Both are considered to have the same +effectiveness in cooling the thermal zone. + +If the processor is listed in _PSL method, and the fan is listed in _AL0 +method, the sys I/F structure will be built like this:: + + /sys/class/thermal: + |thermal_zone1: + |---type: acpitz + |---temp: 37000 + |---mode: enabled + |---policy: step_wise + |---available_policies: step_wise fair_share + |---trip_point_0_temp: 100000 + |---trip_point_0_type: critical + |---trip_point_1_temp: 80000 + |---trip_point_1_type: passive + |---trip_point_2_temp: 70000 + |---trip_point_2_type: active0 + |---trip_point_3_temp: 60000 + |---trip_point_3_type: active1 + |---cdev0: --->/sys/class/thermal/cooling_device0 + |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ + |---cdev0_weight: 1024 + |---cdev1: --->/sys/class/thermal/cooling_device3 + |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ + |---cdev1_weight: 1024 + + |cooling_device0: + |---type: Processor + |---max_state: 8 + |---cur_state: 0 + + |cooling_device3: + |---type: Fan + |---max_state: 2 + |---cur_state: 0 + + /sys/class/hwmon: + |hwmon0: + |---name: acpitz + |---temp1_input: 37000 + |---temp1_crit: 100000 + +4. Export Symbol APIs +===================== + +4.1. get_tz_trend +----------------- + +This function returns the trend of a thermal zone, i.e the rate of change +of temperature of the thermal zone. Ideally, the thermal sensor drivers +are supposed to implement the callback. If they don't, the thermal +framework calculated the trend by comparing the previous and the current +temperature values. + +4.2. get_thermal_instance +------------------------- + +This function returns the thermal_instance corresponding to a given +{thermal_zone, cooling_device, trip_point} combination. Returns NULL +if such an instance does not exist. + +4.3. thermal_notify_framework +----------------------------- + +This function handles the trip events from sensor drivers. It starts +throttling the cooling devices according to the policy configured. +For CRITICAL and HOT trip points, this notifies the respective drivers, +and does actual throttling for other trip points i.e ACTIVE and PASSIVE. +The throttling policy is based on the configured platform data; if no +platform data is provided, this uses the step_wise throttling policy. + +4.4. thermal_cdev_update +------------------------ + +This function serves as an arbitrator to set the state of a cooling +device. It sets the cooling device to the deepest cooling state if +possible. + +5. thermal_emergency_poweroff +============================= + +On an event of critical trip temperature crossing. Thermal framework +allows the system to shutdown gracefully by calling orderly_poweroff(). +In the event of a failure of orderly_poweroff() to shut down the system +we are in danger of keeping the system alive at undesirably high +temperatures. To mitigate this high risk scenario we program a work +queue to fire after a pre-determined number of seconds to start +an emergency shutdown of the device using the kernel_power_off() +function. In case kernel_power_off() fails then finally +emergency_restart() is called in the worst case. + +The delay should be carefully profiled so as to give adequate time for +orderly_poweroff(). In case of failure of an orderly_poweroff() the +emergency poweroff kicks in after the delay has elapsed and shuts down +the system. + +If set to 0 emergency poweroff will not be supported. So a carefully +profiled non-zero positive value is a must for emergerncy poweroff to be +triggered. diff --git a/Documentation/driver-api/thermal/x86_pkg_temperature_thermal.rst b/Documentation/driver-api/thermal/x86_pkg_temperature_thermal.rst new file mode 100644 index 000000000..2ac42ccd2 --- /dev/null +++ b/Documentation/driver-api/thermal/x86_pkg_temperature_thermal.rst @@ -0,0 +1,55 @@ +=================================== +Kernel driver: x86_pkg_temp_thermal +=================================== + +Supported chips: + +* x86: with package level thermal management + +(Verify using: CPUID.06H:EAX[bit 6] =1) + +Authors: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> + +Reference +--------- + +Intel® 64 and IA-32 Architectures Software Developer’s Manual (Jan, 2013): +Chapter 14.6: PACKAGE LEVEL THERMAL MANAGEMENT + +Description +----------- + +This driver register CPU digital temperature package level sensor as a thermal +zone with maximum two user mode configurable trip points. Number of trip points +depends on the capability of the package. Once the trip point is violated, +user mode can receive notification via thermal notification mechanism and can +take any action to control temperature. + + +Threshold management +-------------------- +Each package will register as a thermal zone under /sys/class/thermal. + +Example:: + + /sys/class/thermal/thermal_zone1 + +This contains two trip points: + +- trip_point_0_temp +- trip_point_1_temp + +User can set any temperature between 0 to TJ-Max temperature. Temperature units +are in milli-degree Celsius. Refer to "Documentation/driver-api/thermal/sysfs-api.rst" for +thermal sys-fs details. + +Any value other than 0 in these trip points, can trigger thermal notifications. +Setting 0, stops sending thermal notifications. + +Thermal notifications: +To get kobject-uevent notifications, set the thermal zone +policy to "user_space". + +For example:: + + echo -n "user_space" > policy |