| What: /sys/devices/.../power/ |
| Date: January 2009 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../power directory contains attributes |
| allowing the user space to check and modify some power |
| management related properties of given device. |
| |
| What: /sys/devices/.../power/wakeup |
| Date: January 2009 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../power/wakeup attribute allows the user |
| space to check if the device is enabled to wake up the system |
| from sleep states, such as the memory sleep state (suspend to |
| RAM) and hibernation (suspend to disk), and to enable or disable |
| it to do that as desired. |
| |
| Some devices support "wakeup" events, which are hardware signals |
| used to activate the system from a sleep state. Such devices |
| have one of the following two values for the sysfs power/wakeup |
| file: |
| |
| + "enabled\n" to issue the events; |
| + "disabled\n" not to do so; |
| |
| In that cases the user space can change the setting represented |
| by the contents of this file by writing either "enabled", or |
| "disabled" to it. |
| |
| For the devices that are not capable of generating system wakeup |
| events this file is not present. In that case the device cannot |
| be enabled to wake up the system from sleep states. |
| |
| What: /sys/devices/.../power/control |
| Date: January 2009 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../power/control attribute allows the user |
| space to control the run-time power management of the device. |
| |
| All devices have one of the following two values for the |
| power/control file: |
| |
| + "auto\n" to allow the device to be power managed at run time; |
| + "on\n" to prevent the device from being power managed; |
| |
| The default for all devices is "auto", which means that they may |
| be subject to automatic power management, depending on their |
| drivers. Changing this attribute to "on" prevents the driver |
| from power managing the device at run time. Doing that while |
| the device is suspended causes it to be woken up. |
| |
| What: /sys/devices/.../power/async |
| Date: January 2009 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../async attribute allows the user space to |
| enable or diasble the device's suspend and resume callbacks to |
| be executed asynchronously (ie. in separate threads, in parallel |
| with the main suspend/resume thread) during system-wide power |
| transitions (eg. suspend to RAM, hibernation). |
| |
| All devices have one of the following two values for the |
| power/async file: |
| |
| + "enabled\n" to permit the asynchronous suspend/resume; |
| + "disabled\n" to forbid it; |
| |
| The value of this attribute may be changed by writing either |
| "enabled", or "disabled" to it. |
| |
| It generally is unsafe to permit the asynchronous suspend/resume |
| of a device unless it is certain that all of the PM dependencies |
| of the device are known to the PM core. However, for some |
| devices this attribute is set to "enabled" by bus type code or |
| device drivers and in that cases it should be safe to leave the |
| default value. |
| |
| What: /sys/devices/.../power/wakeup_count |
| Date: September 2010 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_count attribute contains the number |
| of signaled wakeup events associated with the device. This |
| attribute is read-only. If the device is not capable to wake up |
| the system from sleep states, this attribute is not present. |
| If the device is not enabled to wake up the system from sleep |
| states, this attribute is empty. |
| |
| What: /sys/devices/.../power/wakeup_active_count |
| Date: September 2010 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_active_count attribute contains the |
| number of times the processing of wakeup events associated with |
| the device was completed (at the kernel level). This attribute |
| is read-only. If the device is not capable to wake up the |
| system from sleep states, this attribute is not present. If |
| the device is not enabled to wake up the system from sleep |
| states, this attribute is empty. |
| |
| What: /sys/devices/.../power/wakeup_abort_count |
| Date: February 2012 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_abort_count attribute contains the |
| number of times the processing of a wakeup event associated with |
| the device might have aborted system transition into a sleep |
| state in progress. This attribute is read-only. If the device |
| is not capable to wake up the system from sleep states, this |
| attribute is not present. If the device is not enabled to wake |
| up the system from sleep states, this attribute is empty. |
| |
| What: /sys/devices/.../power/wakeup_expire_count |
| Date: February 2012 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_expire_count attribute contains the |
| number of times a wakeup event associated with the device has |
| been reported with a timeout that expired. This attribute is |
| read-only. If the device is not capable to wake up the system |
| from sleep states, this attribute is not present. If the |
| device is not enabled to wake up the system from sleep states, |
| this attribute is empty. |
| |
| What: /sys/devices/.../power/wakeup_active |
| Date: September 2010 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_active attribute contains either 1, |
| or 0, depending on whether or not a wakeup event associated with |
| the device is being processed (1). This attribute is read-only. |
| If the device is not capable to wake up the system from sleep |
| states, this attribute is not present. If the device is not |
| enabled to wake up the system from sleep states, this attribute |
| is empty. |
| |
| What: /sys/devices/.../power/wakeup_total_time_ms |
| Date: September 2010 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_total_time_ms attribute contains |
| the total time of processing wakeup events associated with the |
| device, in milliseconds. This attribute is read-only. If the |
| device is not capable to wake up the system from sleep states, |
| this attribute is not present. If the device is not enabled to |
| wake up the system from sleep states, this attribute is empty. |
| |
| What: /sys/devices/.../power/wakeup_max_time_ms |
| Date: September 2010 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_max_time_ms attribute contains |
| the maximum time of processing a single wakeup event associated |
| with the device, in milliseconds. This attribute is read-only. |
| If the device is not capable to wake up the system from sleep |
| states, this attribute is not present. If the device is not |
| enabled to wake up the system from sleep states, this attribute |
| is empty. |
| |
| What: /sys/devices/.../power/wakeup_last_time_ms |
| Date: September 2010 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_last_time_ms attribute contains |
| the value of the monotonic clock corresponding to the time of |
| signaling the last wakeup event associated with the device, in |
| milliseconds. This attribute is read-only. If the device is |
| not enabled to wake up the system from sleep states, this |
| attribute is not present. If the device is not enabled to wake |
| up the system from sleep states, this attribute is empty. |
| |
| What: /sys/devices/.../power/wakeup_prevent_sleep_time_ms |
| Date: February 2012 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../wakeup_prevent_sleep_time_ms attribute |
| contains the total time the device has been preventing |
| opportunistic transitions to sleep states from occurring. |
| This attribute is read-only. If the device is not capable to |
| wake up the system from sleep states, this attribute is not |
| present. If the device is not enabled to wake up the system |
| from sleep states, this attribute is empty. |
| |
| What: /sys/devices/.../power/autosuspend_delay_ms |
| Date: September 2010 |
| Contact: Alan Stern <stern@rowland.harvard.edu> |
| Description: |
| The /sys/devices/.../power/autosuspend_delay_ms attribute |
| contains the autosuspend delay value (in milliseconds). Some |
| drivers do not want their device to suspend as soon as it |
| becomes idle at run time; they want the device to remain |
| inactive for a certain minimum period of time first. That |
| period is called the autosuspend delay. Negative values will |
| prevent the device from being suspended at run time (similar |
| to writing "on" to the power/control attribute). Values >= |
| 1000 will cause the autosuspend timer expiration to be rounded |
| up to the nearest second. |
| |
| Not all drivers support this attribute. If it isn't supported, |
| attempts to read or write it will yield I/O errors. |
| |
| What: /sys/devices/.../power/pm_qos_resume_latency_us |
| Date: March 2012 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../power/pm_qos_resume_latency_us attribute |
| contains the PM QoS resume latency limit for the given device, |
| which is the maximum allowed time it can take to resume the |
| device, after it has been suspended at run time, from a resume |
| request to the moment the device will be ready to process I/O, |
| in microseconds. If it is equal to 0, however, this means that |
| the PM QoS resume latency may be arbitrary and the special value |
| "n/a" means that user space cannot accept any resume latency at |
| all for the given device. |
| |
| Not all drivers support this attribute. If it isn't supported, |
| it is not present. |
| |
| This attribute has no effect on system-wide suspend/resume and |
| hibernation. |
| |
| What: /sys/devices/.../power/pm_qos_latency_tolerance_us |
| Date: January 2014 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../power/pm_qos_latency_tolerance_us attribute |
| contains the PM QoS active state latency tolerance limit for the |
| given device in microseconds. That is the maximum memory access |
| latency the device can suffer without any visible adverse |
| effects on user space functionality. If that value is the |
| string "any", the latency does not matter to user space at all, |
| but hardware should not be allowed to set the latency tolerance |
| for the device automatically. |
| |
| Reading "auto" from this file means that the maximum memory |
| access latency for the device may be determined automatically |
| by the hardware as needed. Writing "auto" to it allows the |
| hardware to be switched to this mode if there are no other |
| latency tolerance requirements from the kernel side. |
| |
| This attribute is only present if the feature controlled by it |
| is supported by the hardware. |
| |
| This attribute has no effect on runtime suspend and resume of |
| devices and on system-wide suspend/resume and hibernation. |
| |
| What: /sys/devices/.../power/pm_qos_no_power_off |
| Date: September 2012 |
| Contact: Rafael J. Wysocki <rjw@rjwysocki.net> |
| Description: |
| The /sys/devices/.../power/pm_qos_no_power_off attribute |
| is used for manipulating the PM QoS "no power off" flag. If |
| set, this flag indicates to the kernel that power should not |
| be removed entirely from the device. |
| |
| Not all drivers support this attribute. If it isn't supported, |
| it is not present. |
| |
| This attribute has no effect on system-wide suspend/resume and |
| hibernation. |