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Diffstat (limited to 'Documentation/ABI/testing/sysfs-devices-power')
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diff --git a/Documentation/ABI/testing/sysfs-devices-power b/Documentation/ABI/testing/sysfs-devices-power new file mode 100644 index 000000000..80a00f7b6 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-devices-power @@ -0,0 +1,262 @@ +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. |