path: root/Documentation/power
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authorRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-06-28 13:01:40 +0200
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2013-06-28 13:01:40 +0200
commite52cff8bdd4a30c40a7f65c7ea8f1f425f8a15eb (patch)
tree1729332ebab51bb560ca64effe46cdab38ab537f /Documentation/power
parent405a1086bdd091d2d55db0ac905cd6332b35cec1 (diff)
parentf5ce1572109049b90484e2bb44927cb6034c5eb1 (diff)
Merge branch 'pm-assorted'
* pm-assorted: PM / QoS: Add pm_qos and dev_pm_qos to events-power.txt PM / QoS: Add dev_pm_qos_request tracepoints PM / QoS: Add pm_qos_request tracepoints PM / QoS: Add pm_qos_update_target/flags tracepoints PM / QoS: Update Documentation/power/pm_qos_interface.txt PM / Sleep: Print last wakeup source on failed wakeup_count write PM / QoS: correct the valid range of pm_qos_class PM / wakeup: Adjust messaging for wake events during suspend PM / Runtime: Update .runtime_idle() callback documentation PM / Runtime: Rework the "runtime idle" helper routine PM / Hibernate: print physical addresses consistently with other parts of kernel
Diffstat (limited to 'Documentation/power')
2 files changed, 53 insertions, 17 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 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:
-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:
diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 6c9f5d9aa115..71d8fe4e75d3 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -144,8 +144,12 @@ The action performed by the idle callback is totally dependent on the subsystem
(or driver) in question, but the expected and recommended action is to check
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. The value returned by this callback is ignored by the PM
+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.
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
@@ -301,9 +305,10 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
removing the device from device hierarchy
int pm_runtime_idle(struct device *dev);
- - execute the subsystem-level idle callback for the device; returns 0 on
- success or error code on failure, where -EINPROGRESS means that
- ->runtime_idle() is already being executed
+ - 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
int pm_runtime_suspend(struct device *dev);
- execute the subsystem-level suspend callback for the device; returns 0 on
@@ -660,11 +665,6 @@ Subsystems may wish to conserve code space by using the set of generic power
management callbacks provided by the PM core, defined in
- int pm_generic_runtime_idle(struct device *dev);
- - invoke the ->runtime_idle() callback provided by the driver of this
- device, if defined, and call pm_runtime_suspend() for this device if the
- return value is 0 or the callback is not defined
int pm_generic_runtime_suspend(struct device *dev);
- invoke the ->runtime_suspend() callback provided by the driver of this
device and return its result, or return -EINVAL if not defined

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