diff options
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/energy-model.rst | 46 | ||||
| -rw-r--r-- | Documentation/power/opp.rst | 14 | ||||
| -rw-r--r-- | Documentation/power/pci.rst | 2 | ||||
| -rw-r--r-- | Documentation/power/runtime_pm.rst | 14 |
4 files changed, 56 insertions, 20 deletions
diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index 5ac62a7b4b7c..ef341be2882b 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -20,20 +20,20 @@ possible source of information on its own, the EM framework intervenes as an abstraction layer which standardizes the format of power cost tables in the kernel, hence enabling to avoid redundant work. -The power values might be expressed in milli-Watts or in an 'abstract scale'. +The power values might be expressed in micro-Watts or in an 'abstract scale'. Multiple subsystems might use the EM and it is up to the system integrator to check that the requirements for the power value scale types are met. An example can be found in the Energy-Aware Scheduler documentation Documentation/scheduler/sched-energy.rst. For some subsystems like thermal or powercap power values expressed in an 'abstract scale' might cause issues. These subsystems are more interested in estimation of power used in the past, -thus the real milli-Watts might be needed. An example of these requirements can +thus the real micro-Watts might be needed. An example of these requirements can be found in the Intelligent Power Allocation in Documentation/driver-api/thermal/power_allocator.rst. Kernel subsystems might implement automatic detection to check whether EM registered devices have inconsistent scale (based on EM internal flag). Important thing to keep in mind is that when the power values are expressed in -an 'abstract scale' deriving real energy in milli-Joules would not be possible. +an 'abstract scale' deriving real energy in micro-Joules would not be possible. The figure below depicts an example of drivers (Arm-specific here, but the approach is applicable to any architecture) providing power costs to the EM @@ -98,7 +98,7 @@ Drivers are expected to register performance domains into the EM framework by calling the following API:: int em_dev_register_perf_domain(struct device *dev, unsigned int nr_states, - struct em_data_callback *cb, cpumask_t *cpus, bool milliwatts); + struct em_data_callback *cb, cpumask_t *cpus, bool microwatts); Drivers must provide a callback function returning <frequency, power> tuples for each performance state. The callback function provided by the driver is free @@ -106,13 +106,43 @@ to fetch data from any relevant location (DT, firmware, ...), and by any mean deemed necessary. Only for CPU devices, drivers must specify the CPUs of the performance domains using cpumask. For other devices than CPUs the last argument must be set to NULL. -The last argument 'milliwatts' is important to set with correct value. Kernel +The last argument 'microwatts' is important to set with correct value. Kernel subsystems which use EM might rely on this flag to check if all EM devices use the same scale. If there are different scales, these subsystems might decide -to: return warning/error, stop working or panic. +to return warning/error, stop working or panic. See Section 3. for an example of driver implementing this callback, or Section 2.4 for further documentation on this API +Registration of EM using DT +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The EM can also be registered using OPP framework and information in DT +"operating-points-v2". Each OPP entry in DT can be extended with a property +"opp-microwatt" containing micro-Watts power value. This OPP DT property +allows a platform to register EM power values which are reflecting total power +(static + dynamic). These power values might be coming directly from +experiments and measurements. + +Registration of 'artificial' EM +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There is an option to provide a custom callback for drivers missing detailed +knowledge about power value for each performance state. The callback +.get_cost() is optional and provides the 'cost' values used by the EAS. +This is useful for platforms that only provide information on relative +efficiency between CPU types, where one could use the information to +create an abstract power model. But even an abstract power model can +sometimes be hard to fit in, given the input power value size restrictions. +The .get_cost() allows to provide the 'cost' values which reflect the +efficiency of the CPUs. This would allow to provide EAS information which +has different relation than what would be forced by the EM internal +formulas calculating 'cost' values. To register an EM for such platform, the +driver must set the flag 'microwatts' to 0, provide .get_power() callback +and provide .get_cost() callback. The EM framework would handle such platform +properly during registration. A flag EM_PERF_DOMAIN_ARTIFICIAL is set for such +platform. Special care should be taken by other frameworks which are using EM +to test and treat this flag properly. + Registration of 'simple' EM ~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -171,8 +201,8 @@ EM framework:: -> drivers/cpufreq/foo_cpufreq.c - 01 static int est_power(unsigned long *mW, unsigned long *KHz, - 02 struct device *dev) + 01 static int est_power(struct device *dev, unsigned long *mW, + 02 unsigned long *KHz) 03 { 04 long freq, power; 05 diff --git a/Documentation/power/opp.rst b/Documentation/power/opp.rst index e3cc4f349ea8..a7c03c470980 100644 --- a/Documentation/power/opp.rst +++ b/Documentation/power/opp.rst @@ -48,9 +48,9 @@ We can represent these as three OPPs as the following {Hz, uV} tuples: OPP library provides a set of helper functions to organize and query the OPP information. The library is located in drivers/opp/ directory and the header is located in include/linux/pm_opp.h. OPP library can be enabled by enabling -CONFIG_PM_OPP from power management menuconfig menu. OPP library depends on -CONFIG_PM as certain SoCs such as Texas Instrument's OMAP framework allows to -optionally boot at a certain OPP without needing cpufreq. +CONFIG_PM_OPP from power management menuconfig menu. Certain SoCs such as Texas +Instrument's OMAP framework allows to optionally boot at a certain OPP without +needing cpufreq. Typical usage of the OPP library is as follows:: @@ -75,8 +75,8 @@ operations until that OPP could be re-enabled if possible. OPP library facilitates this concept in its implementation. The following operational functions operate only on available opps: -opp_find_freq_{ceil, floor}, dev_pm_opp_get_voltage, dev_pm_opp_get_freq, -dev_pm_opp_get_opp_count +dev_pm_opp_find_freq_{ceil, floor}, dev_pm_opp_get_voltage, dev_pm_opp_get_freq, +dev_pm_opp_get_opp_count. dev_pm_opp_find_freq_exact is meant to be used to find the opp pointer which can then be used for dev_pm_opp_enable/disable functions to make an @@ -103,7 +103,7 @@ dev_pm_opp_add The OPP is defined using the frequency and voltage. Once added, the OPP is assumed to be available and control of its availability can be done with the dev_pm_opp_enable/disable functions. OPP library - internally stores and manages this information in the opp struct. + internally stores and manages this information in the dev_pm_opp struct. This function may be used by SoC framework to define a optimal list as per the demands of SoC usage environment. @@ -247,7 +247,7 @@ dev_pm_opp_disable 5. OPP Data Retrieval Functions =============================== Since OPP library abstracts away the OPP information, a set of functions to pull -information from the OPP structure is necessary. Once an OPP pointer is +information from the dev_pm_opp structure is necessary. Once an OPP pointer is retrieved using the search functions, the following functions can be used by SoC framework to retrieve the information represented inside the OPP layer. diff --git a/Documentation/power/pci.rst b/Documentation/power/pci.rst index b04fb18cc4e2..a125544b4cb6 100644 --- a/Documentation/power/pci.rst +++ b/Documentation/power/pci.rst @@ -315,7 +315,7 @@ that these callbacks operate on:: configuration space */ unsigned int pme_support:5; /* Bitmask of states from which PME# can be generated */ - unsigned int pme_interrupt:1;/* Is native PCIe PME signaling used? */ + unsigned int pme_poll:1; /* Poll device's PME status bit */ unsigned int d1_support:1; /* Low power state D1 is supported */ unsigned int d2_support:1; /* Low power state D2 is supported */ unsigned int no_d1d2:1; /* D1 and D2 are forbidden */ diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst index d6bf84f061f4..65b86e487afe 100644 --- a/Documentation/power/runtime_pm.rst +++ b/Documentation/power/runtime_pm.rst @@ -265,6 +265,10 @@ defined in include/linux/pm.h: RPM_SUSPENDED, which means that each device is initially regarded by the PM core as 'suspended', regardless of its real hardware status + `enum rpm_status last_status;` + - the last runtime PM status of the device captured before disabling runtime + PM for it (invalid initially and when disable_depth is 0) + `unsigned int runtime_auto;` - if set, indicates that the user space has allowed the device driver to power manage the device at run time via the /sys/devices/.../power/control @@ -333,10 +337,12 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: `int pm_runtime_resume(struct device *dev);` - execute the subsystem-level resume callback for the device; returns 0 on - success, 1 if the device's runtime PM status was already 'active' or - error code on failure, where -EAGAIN means it may be safe to attempt to - resume the device again in future, but 'power.runtime_error' should be - checked additionally, and -EACCES means that 'power.disable_depth' is + success, 1 if the device's runtime PM status is already 'active' (also if + 'power.disable_depth' is nonzero, but the status was 'active' when it was + changing from 0 to 1) or error code on failure, where -EAGAIN means it may + be safe to attempt to resume the device again in future, but + 'power.runtime_error' should be checked additionally, and -EACCES means + that the callback could not be run, because 'power.disable_depth' was different from 0 `int pm_runtime_resume_and_get(struct device *dev);` |