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Diffstat (limited to 'Documentation/power/pm_qos_interface.txt')
| -rw-r--r-- | Documentation/power/pm_qos_interface.txt | 50 |
1 files changed, 43 insertions, 7 deletions
diff --git a/Documentation/power/pm_qos_interface.txt b/Documentation/power/pm_qos_interface.txt index 79a2a58425ee..483632087788 100644 --- a/Documentation/power/pm_qos_interface.txt +++ b/Documentation/power/pm_qos_interface.txt @@ -7,7 +7,7 @@ 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. +constraints and PM QoS flags. Each parameters have defined units: * latency: usec @@ -86,13 +86,17 @@ To remove the user mode request for a target value simply close the device node. -2. PM QoS per-device latency framework +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. -For each device 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. @@ -119,6 +123,38 @@ 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: |