diff options
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/powercap/powercap.txt | 236 | ||||
| -rw-r--r-- | Documentation/power/runtime_pm.txt | 14 |
2 files changed, 244 insertions, 6 deletions
diff --git a/Documentation/power/powercap/powercap.txt b/Documentation/power/powercap/powercap.txt new file mode 100644 index 000000000000..1e6ef164e07a --- /dev/null +++ b/Documentation/power/powercap/powercap.txt @@ -0,0 +1,236 @@ +Power Capping Framework +================================== + +The power capping framework provides a consistent interface between the kernel +and the user space that allows power capping drivers to expose the settings to +user space in a uniform way. + +Terminology +========================= +The framework exposes power capping devices to user space via sysfs in the +form of a tree of objects. The objects at the root level of the tree represent +'control types', which correspond to different methods of power capping. For +example, the intel-rapl control type represents the Intel "Running Average +Power Limit" (RAPL) technology, whereas the 'idle-injection' control type +corresponds to the use of idle injection for controlling power. + +Power zones represent different parts of the system, which can be controlled and +monitored using the power capping method determined by the control type the +given zone belongs to. They each contain attributes for monitoring power, as +well as controls represented in the form of power constraints. If the parts of +the system represented by different power zones are hierarchical (that is, one +bigger part consists of multiple smaller parts that each have their own power +controls), those power zones may also be organized in a hierarchy with one +parent power zone containing multiple subzones and so on to reflect the power +control topology of the system. In that case, it is possible to apply power +capping to a set of devices together using the parent power zone and if more +fine grained control is required, it can be applied through the subzones. + + +Example sysfs interface tree: + +/sys/devices/virtual/powercap +??? intel-rapl + ??? intel-rapl:0 + ? ??? constraint_0_name + ? ??? constraint_0_power_limit_uw + ? ??? constraint_0_time_window_us + ? ??? constraint_1_name + ? ??? constraint_1_power_limit_uw + ? ??? constraint_1_time_window_us + ? ??? device -> ../../intel-rapl + ? ??? energy_uj + ? ??? intel-rapl:0:0 + ? ? ??? constraint_0_name + ? ? ??? constraint_0_power_limit_uw + ? ? ??? constraint_0_time_window_us + ? ? ??? constraint_1_name + ? ? ??? constraint_1_power_limit_uw + ? ? ??? constraint_1_time_window_us + ? ? ??? device -> ../../intel-rapl:0 + ? ? ??? energy_uj + ? ? ??? max_energy_range_uj + ? ? ??? name + ? ? ??? enabled + ? ? ??? power + ? ? ? ??? async + ? ? ? [] + ? ? ??? subsystem -> ../../../../../../class/power_cap + ? ? ??? uevent + ? ??? intel-rapl:0:1 + ? ? ??? constraint_0_name + ? ? ??? constraint_0_power_limit_uw + ? ? ??? constraint_0_time_window_us + ? ? ??? constraint_1_name + ? ? ??? constraint_1_power_limit_uw + ? ? ??? constraint_1_time_window_us + ? ? ??? device -> ../../intel-rapl:0 + ? ? ??? energy_uj + ? ? ??? max_energy_range_uj + ? ? ??? name + ? ? ??? enabled + ? ? ??? power + ? ? ? ??? async + ? ? ? [] + ? ? ??? subsystem -> ../../../../../../class/power_cap + ? ? ??? uevent + ? ??? max_energy_range_uj + ? ??? max_power_range_uw + ? ??? name + ? ??? enabled + ? ??? power + ? ? ??? async + ? ? [] + ? ??? subsystem -> ../../../../../class/power_cap + ? ??? enabled + ? ??? uevent + ??? intel-rapl:1 + ? ??? constraint_0_name + ? ??? constraint_0_power_limit_uw + ? ??? constraint_0_time_window_us + ? ??? constraint_1_name + ? ??? constraint_1_power_limit_uw + ? ??? constraint_1_time_window_us + ? ??? device -> ../../intel-rapl + ? ??? energy_uj + ? ??? intel-rapl:1:0 + ? ? ??? constraint_0_name + ? ? ??? constraint_0_power_limit_uw + ? ? ??? constraint_0_time_window_us + ? ? ??? constraint_1_name + ? ? ??? constraint_1_power_limit_uw + ? ? ??? constraint_1_time_window_us + ? ? ??? device -> ../../intel-rapl:1 + ? ? ??? energy_uj + ? ? ??? max_energy_range_uj + ? ? ??? name + ? ? ??? enabled + ? ? ??? power + ? ? ? ??? async + ? ? ? [] + ? ? ??? subsystem -> ../../../../../../class/power_cap + ? ? ??? uevent + ? ??? intel-rapl:1:1 + ? ? ??? constraint_0_name + ? ? ??? constraint_0_power_limit_uw + ? ? ??? constraint_0_time_window_us + ? ? ??? constraint_1_name + ? ? ??? constraint_1_power_limit_uw + ? ? ??? constraint_1_time_window_us + ? ? ??? device -> ../../intel-rapl:1 + ? ? ??? energy_uj + ? ? ??? max_energy_range_uj + ? ? ??? name + ? ? ??? enabled + ? ? ??? power + ? ? ? ??? async + ? ? ? [] + ? ? ??? subsystem -> ../../../../../../class/power_cap + ? ? ??? uevent + ? ??? max_energy_range_uj + ? ??? max_power_range_uw + ? ??? name + ? ??? enabled + ? ??? power + ? ? ??? async + ? ? [] + ? ??? subsystem -> ../../../../../class/power_cap + ? ??? uevent + ??? power + ? ??? async + ? [] + ??? subsystem -> ../../../../class/power_cap + ??? enabled + ??? uevent + +The above example illustrates a case in which the Intel RAPL technology, +available in Intel® IA-64 and IA-32 Processor Architectures, is used. There is one +control type called intel-rapl which contains two power zones, intel-rapl:0 and +intel-rapl:1, representing CPU packages. Each of these power zones contains +two subzones, intel-rapl:j:0 and intel-rapl:j:1 (j = 0, 1), representing the +"core" and the "uncore" parts of the given CPU package, respectively. All of +the zones and subzones contain energy monitoring attributes (energy_uj, +max_energy_range_uj) and constraint attributes (constraint_*) allowing controls +to be applied (the constraints in the 'package' power zones apply to the whole +CPU packages and the subzone constraints only apply to the respective parts of +the given package individually). Since Intel RAPL doesn't provide instantaneous +power value, there is no power_uw attribute. + +In addition to that, each power zone contains a name attribute, allowing the +part of the system represented by that zone to be identified. +For example: + +cat /sys/class/power_cap/intel-rapl/intel-rapl:0/name +package-0 + +The Intel RAPL technology allows two constraints, short term and long term, +with two different time windows to be applied to each power zone. Thus for +each zone there are 2 attributes representing the constraint names, 2 power +limits and 2 attributes representing the sizes of the time windows. Such that, +constraint_j_* attributes correspond to the jth constraint (j = 0,1). + +For example: + constraint_0_name + constraint_0_power_limit_uw + constraint_0_time_window_us + constraint_1_name + constraint_1_power_limit_uw + constraint_1_time_window_us + +Power Zone Attributes +================================= +Monitoring attributes +---------------------- + +energy_uj (rw): Current energy counter in micro joules. Write "0" to reset. +If the counter can not be reset, then this attribute is read only. + +max_energy_range_uj (ro): Range of the above energy counter in micro-joules. + +power_uw (ro): Current power in micro watts. + +max_power_range_uw (ro): Range of the above power value in micro-watts. + +name (ro): Name of this power zone. + +It is possible that some domains have both power ranges and energy counter ranges; +however, only one is mandatory. + +Constraints +---------------- +constraint_X_power_limit_uw (rw): Power limit in micro watts, which should be +applicable for the time window specified by "constraint_X_time_window_us". + +constraint_X_time_window_us (rw): Time window in micro seconds. + +constraint_X_name (ro): An optional name of the constraint + +constraint_X_max_power_uw(ro): Maximum allowed power in micro watts. + +constraint_X_min_power_uw(ro): Minimum allowed power in micro watts. + +constraint_X_max_time_window_us(ro): Maximum allowed time window in micro seconds. + +constraint_X_min_time_window_us(ro): Minimum allowed time window in micro seconds. + +Except power_limit_uw and time_window_us other fields are optional. + +Common zone and control type attributes +---------------------------------------- +enabled (rw): Enable/Disable controls at zone level or for all zones using +a control type. + +Power Cap Client Driver Interface +================================== +The API summary: + +Call powercap_register_control_type() to register control type object. +Call powercap_register_zone() to register a power zone (under a given +control type), either as a top-level power zone or as a subzone of another +power zone registered earlier. +The number of constraints in a power zone and the corresponding callbacks have +to be defined prior to calling powercap_register_zone() to register that zone. + +To Free a power zone call powercap_unregister_zone(). +To free a control type object call powercap_unregister_control_type(). +Detailed API can be generated using kernel-doc on include/linux/powercap.h. diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt index 71d8fe4e75d3..0f54333b0ff2 100644 --- a/Documentation/power/runtime_pm.txt +++ b/Documentation/power/runtime_pm.txt @@ -145,11 +145,13 @@ The action performed by the idle callback is totally dependent on the subsystem if the device can be suspended (i.e. if all of the conditions necessary for suspending the device are satisfied) and to queue up a suspend request for the device in that case. If there is no idle callback, or if the callback returns -0, then the PM core will attempt to carry out a runtime suspend of the device; -in essence, it will call pm_runtime_suspend() directly. To prevent this (for -example, if the callback routine has started a delayed suspend), the routine -should return a non-zero value. Negative error return codes are ignored by the -PM core. +0, then the PM core will attempt to carry out a runtime suspend of the device, +also respecting devices configured for autosuspend. In essence this means a +call to pm_runtime_autosuspend() (do note that drivers needs to update the +device last busy mark, pm_runtime_mark_last_busy(), to control the delay under +this circumstance). To prevent this (for example, if the callback routine has +started a delayed suspend), the routine must return a non-zero value. Negative +error return codes are ignored by the PM core. The helper functions provided by the PM core, described in Section 4, guarantee that the following constraints are met with respect to runtime PM callbacks for @@ -308,7 +310,7 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: - execute the subsystem-level idle callback for the device; returns an error code on failure, where -EINPROGRESS means that ->runtime_idle() is already being executed; if there is no callback or the callback returns 0 - then run pm_runtime_suspend(dev) and return its result + then run pm_runtime_autosuspend(dev) and return its result int pm_runtime_suspend(struct device *dev); - execute the subsystem-level suspend callback for the device; returns 0 on |
