linux/Documentation/driver-api/thermal/cpu-cooling-api.rst

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thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
CPU cooling APIs How To
=======================
thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
Written by Amit Daniel Kachhap <amit.kachhap@linaro.org>
Updated: 6 Jan 2015
thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
Copyright (c) 2012 Samsung Electronics Co., Ltd(http://www.samsung.com)
0. Introduction
===============
thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
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
===================
thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
1.1 cpufreq registration/unregistration APIs
--------------------------------------------
::
struct thermal_cooling_device
*cpufreq_cooling_register(struct cpumask *clip_cpus)
thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
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.
::
thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
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)
thermal: add generic cpufreq cooling implementation This patchset introduces a new generic cooling device based on cpufreq that can be used on non-ACPI platforms. As a proof of concept, we have drivers for the following platforms using this mechanism now: * Samsung Exynos (Exynos4 and Exynos5) in the current patchset. * Freescale i.MX (git://git.linaro.org/people/amitdanielk/linux.git imx6q_thermal) There is a small change in cpufreq cooling registration APIs, so a minor change is needed for Freescale platforms. Brief Description: 1) The generic cooling devices code is placed inside driver/thermal/* as placing inside acpi folder will need un-necessary enabling of acpi code. This code is architecture independent. 2) This patchset adds generic cpu cooling low level implementation through frequency clipping. In future, other cpu related cooling devices may be added here. An ACPI version of this already exists (drivers/acpi/processor_thermal.c) .But this will be useful for platforms like ARM using the generic thermal interface along with the generic cpu cooling devices. The cooling device registration API's return cooling device pointers which can be easily binded with the thermal zone trip points. The important APIs exposed are, a) struct thermal_cooling_device *cpufreq_cooling_register( struct cpumask *clip_cpus) b) void cpufreq_cooling_unregister(struct thermal_cooling_device *cdev) 3) Samsung exynos platform thermal implementation is done using the generic cpu cooling APIs and the new trip type. The temperature sensor driver present in the hwmon folder(registered as hwmon driver) is moved to thermal folder and registered as a thermal driver. A simple data/control flow diagrams is shown below, Core Linux thermal <-----> Exynos thermal interface <----- Temperature Sensor | | \|/ | Cpufreq cooling device <--------------- TODO: *Will send the DT enablement patches later after the driver is merged. This patch: Add support for generic cpu thermal cooling low level implementations using frequency scaling up/down based on the registration parameters. Different cpu related cooling devices can be registered by the user and the binding of these cooling devices to the corresponding trip points can be easily done as the registration APIs return the cooling device pointer. The user of these APIs are responsible for passing clipping frequency . The drivers can also register to recieve notification about any cooling action called. [akpm@linux-foundation.org: fix comment layout] Signed-off-by: Amit Daniel Kachhap <amit.kachhap@linaro.org> Cc: Guenter Roeck <guenter.roeck@ericsson.com> Cc: SangWook Ju <sw.ju@samsung.com> Cc: Durgadoss <durgadoss.r@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jean Delvare <khali@linux-fr.org> Cc: Kyungmin Park <kmpark@infradead.org> Cc: Kukjin Kim <kgene.kim@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Amit Daniel Kachhap <amit.daniel@samsung.com> Signed-off-by: Zhang Rui <rui.zhang@intel.com>
2012-08-16 19:41:40 +08:00
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.