|author||lan,Tianyu <firstname.lastname@example.org>||2013-06-21 10:09:15 +0800|
|committer||Rafael J. Wysocki <email@example.com>||2013-06-23 00:56:09 +0200|
PM / QoS: Update Documentation/power/pm_qos_interface.txt
Update PM QoS documentation after recent changes. [rjw: Changelog] Signed-off-by: Lan Tianyu <firstname.lastname@example.org> Signed-off-by: Rafael J. Wysocki <email@example.com>
Diffstat (limited to 'Documentation/power')
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
@@ -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 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
-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.
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.
+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.
+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.
The per-device PM QoS framework has 2 different and distinct notification trees: