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Diffstat (limited to 'Documentation/power/pm_qos_interface.txt')
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diff --git a/Documentation/power/pm_qos_interface.txt b/Documentation/power/pm_qos_interface.txt deleted file mode 100644 index 483632087788..000000000000 --- a/Documentation/power/pm_qos_interface.txt +++ /dev/null @@ -1,184 +0,0 @@ -PM Quality Of Service Interface. - -This interface provides a kernel and user mode interface for registering -performance expectations by drivers, subsystems and user space applications on -one of the parameters. - -Two different PM QoS frameworks are available: -1. PM QoS classes for cpu_dma_latency, network_latency, network_throughput. -2. the per-device PM QoS framework provides the API to manage the per-device latency -constraints and PM QoS flags. - -Each parameters have defined units: - * latency: usec - * timeout: usec - * throughput: kbs (kilo bit / sec) - - -1. PM QoS framework - -The infrastructure exposes multiple misc device nodes one per implemented -parameter. The set of parameters implement is defined by pm_qos_power_init() -and pm_qos_params.h. This is done because having the available parameters -being runtime configurable or changeable from a driver was seen as too easy to -abuse. - -For each parameter a list of performance requests is maintained along with -an aggregated target value. The aggregated target value is updated with -changes to the request list or elements of the list. Typically the -aggregated target value is simply the max or min of the request values held -in the parameter list elements. -Note: the aggregated target value is implemented as an atomic variable so that -reading the aggregated value does not require any locking mechanism. - - -From kernel mode the use of this interface is simple: - -void pm_qos_add_request(handle, param_class, target_value): -Will insert an element into the list for that identified PM QoS class with the -target value. Upon change to this list the new target is recomputed and any -registered notifiers are called only if the target value is now different. -Clients of pm_qos need to save the returned handle for future use in other -pm_qos API functions. - -void pm_qos_update_request(handle, new_target_value): -Will update the list element pointed to by the handle with the new target value -and recompute the new aggregated target, calling the notification tree if the -target is changed. - -void pm_qos_remove_request(handle): -Will remove the element. After removal it will update the aggregate target and -call the notification tree if the target was changed as a result of removing -the request. - -int pm_qos_request(param_class): -Returns the aggregated value for a given PM QoS class. - -int pm_qos_request_active(handle): -Returns if the request is still active, i.e. it has not been removed from a -PM QoS class constraints list. - -int pm_qos_add_notifier(param_class, notifier): -Adds a notification callback function to the PM QoS class. The callback is -called when the aggregated value for the PM QoS class is changed. - -int pm_qos_remove_notifier(int param_class, notifier): -Removes the notification callback function for the PM QoS class. - - -From user mode: -Only processes can register a pm_qos request. To provide for automatic -cleanup of a process, the interface requires the process to register its -parameter requests in the following way: - -To register the default pm_qos target for the specific parameter, the process -must open one of /dev/[cpu_dma_latency, network_latency, network_throughput] - -As long as the device node is held open that process has a registered -request on the parameter. - -To change the requested target value the process needs to write an s32 value to -the open device node. Alternatively the user mode program could write a hex -string for the value using 10 char long format e.g. "0x12345678". This -translates to a pm_qos_update_request call. - -To remove the user mode request for a target value simply close the device -node. - - -2. PM QoS per-device latency and flags framework - -For each device, there are two lists of PM QoS requests. One is maintained -along with the aggregated target of latency value and the other is for PM QoS -flags. Values are updated in response to changes of the request list. - -Target latency value is simply the minimum of the request values held in the -parameter list elements. The PM QoS flags aggregate value is a gather (bitwise -OR) of all list elements' values. Two device PM QoS flags are defined currently: -PM_QOS_FLAG_NO_POWER_OFF and PM_QOS_FLAG_REMOTE_WAKEUP. - -Note: the aggregated target value is implemented as an atomic variable so that -reading the aggregated value does not require any locking mechanism. - - -From kernel mode the use of this interface is the following: - -int dev_pm_qos_add_request(device, handle, type, value): -Will insert an element into the list for that identified device with the -target value. Upon change to this list the new target is recomputed and any -registered notifiers are called only if the target value is now different. -Clients of dev_pm_qos need to save the handle for future use in other -dev_pm_qos API functions. - -int dev_pm_qos_update_request(handle, new_value): -Will update the list element pointed to by the handle with the new target value -and recompute the new aggregated target, calling the notification trees if the -target is changed. - -int dev_pm_qos_remove_request(handle): -Will remove the element. After removal it will update the aggregate target and -call the notification trees if the target was changed as a result of removing -the request. - -s32 dev_pm_qos_read_value(device): -Returns the aggregated value for a given device's constraints list. - -enum pm_qos_flags_status dev_pm_qos_flags(device, mask) -Check PM QoS flags of the given device against the given mask of flags. -The meaning of the return values is as follows: - PM_QOS_FLAGS_ALL: All flags from the mask are set - PM_QOS_FLAGS_SOME: Some flags from the mask are set - PM_QOS_FLAGS_NONE: No flags from the mask are set - PM_QOS_FLAGS_UNDEFINED: The device's PM QoS structure has not been - initialized or the list of requests is empty. - -int dev_pm_qos_add_ancestor_request(dev, handle, value) -Add a PM QoS request for the first direct ancestor of the given device whose -power.ignore_children flag is unset. - -int dev_pm_qos_expose_latency_limit(device, value) -Add a request to the device's PM QoS list of latency constraints and create -a sysfs attribute pm_qos_resume_latency_us under the device's power directory -allowing user space to manipulate that request. - -void dev_pm_qos_hide_latency_limit(device) -Drop the request added by dev_pm_qos_expose_latency_limit() from the device's -PM QoS list of latency constraints and remove sysfs attribute pm_qos_resume_latency_us -from the device's power directory. - -int dev_pm_qos_expose_flags(device, value) -Add a request to the device's PM QoS list of flags and create sysfs attributes -pm_qos_no_power_off and pm_qos_remote_wakeup under the device's power directory -allowing user space to change these flags' value. - -void dev_pm_qos_hide_flags(device) -Drop the request added by dev_pm_qos_expose_flags() from the device's PM QoS list -of flags and remove sysfs attributes pm_qos_no_power_off and pm_qos_remote_wakeup -under the device's power directory. - -Notification mechanisms: -The per-device PM QoS framework has 2 different and distinct notification trees: -a per-device notification tree and a global notification tree. - -int dev_pm_qos_add_notifier(device, notifier): -Adds a notification callback function for the device. -The callback is called when the aggregated value of the device constraints list -is changed. - -int dev_pm_qos_remove_notifier(device, notifier): -Removes the notification callback function for the device. - -int dev_pm_qos_add_global_notifier(notifier): -Adds a notification callback function in the global notification tree of the -framework. -The callback is called when the aggregated value for any device is changed. - -int dev_pm_qos_remove_global_notifier(notifier): -Removes the notification callback function from the global notification tree -of the framework. - - -From user mode: -No API for user space access to the per-device latency constraints is provided -yet - still under discussion. - |