diff options
Diffstat (limited to 'Documentation/power')
-rw-r--r-- | Documentation/power/pm_qos_interface.txt | 37 |
1 files changed, 16 insertions, 21 deletions
diff --git a/Documentation/power/pm_qos_interface.txt b/Documentation/power/pm_qos_interface.txt index 483632087788..22cb8f51182a 100644 --- a/Documentation/power/pm_qos_interface.txt +++ b/Documentation/power/pm_qos_interface.txt | |||
@@ -89,16 +89,16 @@ node. | |||
89 | 2. PM QoS per-device latency and flags framework | 89 | 2. PM QoS per-device latency and flags framework |
90 | 90 | ||
91 | For each device, there are two lists of PM QoS requests. One is maintained | 91 | For each device, there are two lists of PM QoS requests. One is maintained |
92 | along with the aggregated target of latency value and the other is for PM QoS | 92 | along with the aggregated target of resume latency value and the other is for |
93 | flags. Values are updated in response to changes of the request list. | 93 | PM QoS flags. Values are updated in response to changes of the request list. |
94 | 94 | ||
95 | Target latency value is simply the minimum of the request values held in the | 95 | Target resume latency value is simply the minimum of the request values held in |
96 | parameter list elements. The PM QoS flags aggregate value is a gather (bitwise | 96 | the parameter list elements. The PM QoS flags aggregate value is a gather |
97 | OR) of all list elements' values. Two device PM QoS flags are defined currently: | 97 | (bitwise OR) of all list elements' values. Two device PM QoS flags are defined |
98 | PM_QOS_FLAG_NO_POWER_OFF and PM_QOS_FLAG_REMOTE_WAKEUP. | 98 | currently: PM_QOS_FLAG_NO_POWER_OFF and PM_QOS_FLAG_REMOTE_WAKEUP. |
99 | 99 | ||
100 | Note: the aggregated target value is implemented as an atomic variable so that | 100 | Note: the aggregated target value is implemented in such a way that reading the |
101 | reading the aggregated value does not require any locking mechanism. | 101 | aggregated value does not require any locking mechanism. |
102 | 102 | ||
103 | 103 | ||
104 | From kernel mode the use of this interface is the following: | 104 | From kernel mode the use of this interface is the following: |
@@ -137,14 +137,14 @@ Add a PM QoS request for the first direct ancestor of the given device whose | |||
137 | power.ignore_children flag is unset. | 137 | power.ignore_children flag is unset. |
138 | 138 | ||
139 | int dev_pm_qos_expose_latency_limit(device, value) | 139 | int dev_pm_qos_expose_latency_limit(device, value) |
140 | Add a request to the device's PM QoS list of latency constraints and create | 140 | Add a request to the device's PM QoS list of resume latency constraints and |
141 | a sysfs attribute pm_qos_resume_latency_us under the device's power directory | 141 | create a sysfs attribute pm_qos_resume_latency_us under the device's power |
142 | allowing user space to manipulate that request. | 142 | directory allowing user space to manipulate that request. |
143 | 143 | ||
144 | void dev_pm_qos_hide_latency_limit(device) | 144 | void dev_pm_qos_hide_latency_limit(device) |
145 | Drop the request added by dev_pm_qos_expose_latency_limit() from the device's | 145 | Drop the request added by dev_pm_qos_expose_latency_limit() from the device's |
146 | PM QoS list of latency constraints and remove sysfs attribute pm_qos_resume_latency_us | 146 | PM QoS list of resume latency constraints and remove sysfs attribute |
147 | from the device's power directory. | 147 | pm_qos_resume_latency_us from the device's power directory. |
148 | 148 | ||
149 | int dev_pm_qos_expose_flags(device, value) | 149 | int dev_pm_qos_expose_flags(device, value) |
150 | Add a request to the device's PM QoS list of flags and create sysfs attributes | 150 | Add a request to the device's PM QoS list of flags and create sysfs attributes |
@@ -163,7 +163,7 @@ a per-device notification tree and a global notification tree. | |||
163 | int dev_pm_qos_add_notifier(device, notifier): | 163 | int dev_pm_qos_add_notifier(device, notifier): |
164 | Adds a notification callback function for the device. | 164 | Adds a notification callback function for the device. |
165 | The callback is called when the aggregated value of the device constraints list | 165 | The callback is called when the aggregated value of the device constraints list |
166 | is changed. | 166 | is changed (for resume latency device PM QoS only). |
167 | 167 | ||
168 | int dev_pm_qos_remove_notifier(device, notifier): | 168 | int dev_pm_qos_remove_notifier(device, notifier): |
169 | Removes the notification callback function for the device. | 169 | Removes the notification callback function for the device. |
@@ -171,14 +171,9 @@ Removes the notification callback function for the device. | |||
171 | int dev_pm_qos_add_global_notifier(notifier): | 171 | int dev_pm_qos_add_global_notifier(notifier): |
172 | Adds a notification callback function in the global notification tree of the | 172 | Adds a notification callback function in the global notification tree of the |
173 | framework. | 173 | framework. |
174 | The callback is called when the aggregated value for any device is changed. | 174 | The callback is called when the aggregated value for any device is changed |
175 | (for resume latency device PM QoS only). | ||
175 | 176 | ||
176 | int dev_pm_qos_remove_global_notifier(notifier): | 177 | int dev_pm_qos_remove_global_notifier(notifier): |
177 | Removes the notification callback function from the global notification tree | 178 | Removes the notification callback function from the global notification tree |
178 | of the framework. | 179 | of the framework. |
179 | |||
180 | |||
181 | From user mode: | ||
182 | No API for user space access to the per-device latency constraints is provided | ||
183 | yet - still under discussion. | ||
184 | |||