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