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271 lines
11 KiB
271 lines
11 KiB
What: /sys/devices/.../power/ |
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Date: January 2009 |
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Contact: Rafael J. Wysocki <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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 <[email protected]> |
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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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What: /sys/devices/.../power/runtime_status |
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Date: April 2010 |
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Contact: Rafael J. Wysocki <[email protected]> |
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Description: |
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The /sys/devices/.../power/runtime_status attribute contains |
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the current runtime PM status of the device, which may be |
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"suspended", "suspending", "resuming", "active", "error" (fatal |
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error), or "unsupported" (runtime PM is disabled).
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