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1What: /sys/devices/.../power/2Date: January 20093Contact: Rafael J. Wysocki <rjw@rjwysocki.net>4Description:5 The /sys/devices/.../power directory contains attributes6 allowing the user space to check and modify some power7 management related properties of given device.8 9What: /sys/devices/.../power/wakeup10Date: January 200911Contact: Rafael J. Wysocki <rjw@rjwysocki.net>12Description:13 The /sys/devices/.../power/wakeup attribute allows the user14 space to check if the device is enabled to wake up the system15 from sleep states, such as the memory sleep state (suspend to16 RAM) and hibernation (suspend to disk), and to enable or disable17 it to do that as desired.18 19 Some devices support "wakeup" events, which are hardware signals20 used to activate the system from a sleep state. Such devices21 have one of the following two values for the sysfs power/wakeup22 file:23 24 + "enabled\n" to issue the events;25 + "disabled\n" not to do so;26 27 In that cases the user space can change the setting represented28 by the contents of this file by writing either "enabled", or29 "disabled" to it.30 31 For the devices that are not capable of generating system wakeup32 events this file is not present. In that case the device cannot33 be enabled to wake up the system from sleep states.34 35What: /sys/devices/.../power/control36Date: January 200937Contact: Rafael J. Wysocki <rjw@rjwysocki.net>38Description:39 The /sys/devices/.../power/control attribute allows the user40 space to control the run-time power management of the device.41 42 All devices have one of the following two values for the43 power/control file:44 45 + "auto\n" to allow the device to be power managed at run time;46 + "on\n" to prevent the device from being power managed;47 48 The default for all devices is "auto", which means that they may49 be subject to automatic power management, depending on their50 drivers. Changing this attribute to "on" prevents the driver51 from power managing the device at run time. Doing that while52 the device is suspended causes it to be woken up.53 54What: /sys/devices/.../power/async55Date: January 200956Contact: Rafael J. Wysocki <rjw@rjwysocki.net>57Description:58 The /sys/devices/.../async attribute allows the user space to59 enable or diasble the device's suspend and resume callbacks to60 be executed asynchronously (ie. in separate threads, in parallel61 with the main suspend/resume thread) during system-wide power62 transitions (eg. suspend to RAM, hibernation).63 64 All devices have one of the following two values for the65 power/async file:66 67 + "enabled\n" to permit the asynchronous suspend/resume;68 + "disabled\n" to forbid it;69 70 The value of this attribute may be changed by writing either71 "enabled", or "disabled" to it.72 73 It generally is unsafe to permit the asynchronous suspend/resume74 of a device unless it is certain that all of the PM dependencies75 of the device are known to the PM core. However, for some76 devices this attribute is set to "enabled" by bus type code or77 device drivers and in that cases it should be safe to leave the78 default value.79 80What: /sys/devices/.../power/wakeup_count81Date: September 201082Contact: Rafael J. Wysocki <rjw@rjwysocki.net>83Description:84 The /sys/devices/.../wakeup_count attribute contains the number85 of signaled wakeup events associated with the device. This86 attribute is read-only. If the device is not capable to wake up87 the system from sleep states, this attribute is not present.88 If the device is not enabled to wake up the system from sleep89 states, this attribute is empty.90 91What: /sys/devices/.../power/wakeup_active_count92Date: September 201093Contact: Rafael J. Wysocki <rjw@rjwysocki.net>94Description:95 The /sys/devices/.../wakeup_active_count attribute contains the96 number of times the processing of wakeup events associated with97 the device was completed (at the kernel level). This attribute98 is read-only. If the device is not capable to wake up the99 system from sleep states, this attribute is not present. If100 the device is not enabled to wake up the system from sleep101 states, this attribute is empty.102 103What: /sys/devices/.../power/wakeup_abort_count104Date: February 2012105Contact: Rafael J. Wysocki <rjw@rjwysocki.net>106Description:107 The /sys/devices/.../wakeup_abort_count attribute contains the108 number of times the processing of a wakeup event associated with109 the device might have aborted system transition into a sleep110 state in progress. This attribute is read-only. If the device111 is not capable to wake up the system from sleep states, this112 attribute is not present. If the device is not enabled to wake113 up the system from sleep states, this attribute is empty.114 115What: /sys/devices/.../power/wakeup_expire_count116Date: February 2012117Contact: Rafael J. Wysocki <rjw@rjwysocki.net>118Description:119 The /sys/devices/.../wakeup_expire_count attribute contains the120 number of times a wakeup event associated with the device has121 been reported with a timeout that expired. This attribute is122 read-only. If the device is not capable to wake up the system123 from sleep states, this attribute is not present. If the124 device is not enabled to wake up the system from sleep states,125 this attribute is empty.126 127What: /sys/devices/.../power/wakeup_active128Date: September 2010129Contact: Rafael J. Wysocki <rjw@rjwysocki.net>130Description:131 The /sys/devices/.../wakeup_active attribute contains either 1,132 or 0, depending on whether or not a wakeup event associated with133 the device is being processed (1). This attribute is read-only.134 If the device is not capable to wake up the system from sleep135 states, this attribute is not present. If the device is not136 enabled to wake up the system from sleep states, this attribute137 is empty.138 139What: /sys/devices/.../power/wakeup_total_time_ms140Date: September 2010141Contact: Rafael J. Wysocki <rjw@rjwysocki.net>142Description:143 The /sys/devices/.../wakeup_total_time_ms attribute contains144 the total time of processing wakeup events associated with the145 device, in milliseconds. This attribute is read-only. If the146 device is not capable to wake up the system from sleep states,147 this attribute is not present. If the device is not enabled to148 wake up the system from sleep states, this attribute is empty.149 150What: /sys/devices/.../power/wakeup_max_time_ms151Date: September 2010152Contact: Rafael J. Wysocki <rjw@rjwysocki.net>153Description:154 The /sys/devices/.../wakeup_max_time_ms attribute contains155 the maximum time of processing a single wakeup event associated156 with the device, in milliseconds. This attribute is read-only.157 If the device is not capable to wake up the system from sleep158 states, this attribute is not present. If the device is not159 enabled to wake up the system from sleep states, this attribute160 is empty.161 162What: /sys/devices/.../power/wakeup_last_time_ms163Date: September 2010164Contact: Rafael J. Wysocki <rjw@rjwysocki.net>165Description:166 The /sys/devices/.../wakeup_last_time_ms attribute contains167 the value of the monotonic clock corresponding to the time of168 signaling the last wakeup event associated with the device, in169 milliseconds. This attribute is read-only. If the device is170 not enabled to wake up the system from sleep states, this171 attribute is not present. If the device is not enabled to wake172 up the system from sleep states, this attribute is empty.173 174What: /sys/devices/.../power/wakeup_prevent_sleep_time_ms175Date: February 2012176Contact: Rafael J. Wysocki <rjw@rjwysocki.net>177Description:178 The /sys/devices/.../wakeup_prevent_sleep_time_ms attribute179 contains the total time the device has been preventing180 opportunistic transitions to sleep states from occurring.181 This attribute is read-only. If the device is not capable to182 wake up the system from sleep states, this attribute is not183 present. If the device is not enabled to wake up the system184 from sleep states, this attribute is empty.185 186What: /sys/devices/.../power/autosuspend_delay_ms187Date: September 2010188Contact: Alan Stern <stern@rowland.harvard.edu>189Description:190 The /sys/devices/.../power/autosuspend_delay_ms attribute191 contains the autosuspend delay value (in milliseconds). Some192 drivers do not want their device to suspend as soon as it193 becomes idle at run time; they want the device to remain194 inactive for a certain minimum period of time first. That195 period is called the autosuspend delay. Negative values will196 prevent the device from being suspended at run time (similar197 to writing "on" to the power/control attribute). Values >=198 1000 will cause the autosuspend timer expiration to be rounded199 up to the nearest second.200 201 Not all drivers support this attribute. If it isn't supported,202 attempts to read or write it will yield I/O errors.203 204What: /sys/devices/.../power/pm_qos_resume_latency_us205Date: March 2012206Contact: Rafael J. Wysocki <rjw@rjwysocki.net>207Description:208 The /sys/devices/.../power/pm_qos_resume_latency_us attribute209 contains the PM QoS resume latency limit for the given device,210 which is the maximum allowed time it can take to resume the211 device, after it has been suspended at run time, from a resume212 request to the moment the device will be ready to process I/O,213 in microseconds. If it is equal to 0, however, this means that214 the PM QoS resume latency may be arbitrary and the special value215 "n/a" means that user space cannot accept any resume latency at216 all for the given device.217 218 Not all drivers support this attribute. If it isn't supported,219 it is not present.220 221 This attribute has no effect on system-wide suspend/resume and222 hibernation.223 224What: /sys/devices/.../power/pm_qos_latency_tolerance_us225Date: January 2014226Contact: Rafael J. Wysocki <rjw@rjwysocki.net>227Description:228 The /sys/devices/.../power/pm_qos_latency_tolerance_us attribute229 contains the PM QoS active state latency tolerance limit for the230 given device in microseconds. That is the maximum memory access231 latency the device can suffer without any visible adverse232 effects on user space functionality. If that value is the233 string "any", the latency does not matter to user space at all,234 but hardware should not be allowed to set the latency tolerance235 for the device automatically.236 237 Reading "auto" from this file means that the maximum memory238 access latency for the device may be determined automatically239 by the hardware as needed. Writing "auto" to it allows the240 hardware to be switched to this mode if there are no other241 latency tolerance requirements from the kernel side.242 243 This attribute is only present if the feature controlled by it244 is supported by the hardware.245 246 This attribute has no effect on runtime suspend and resume of247 devices and on system-wide suspend/resume and hibernation.248 249What: /sys/devices/.../power/pm_qos_no_power_off250Date: September 2012251Contact: Rafael J. Wysocki <rjw@rjwysocki.net>252Description:253 The /sys/devices/.../power/pm_qos_no_power_off attribute254 is used for manipulating the PM QoS "no power off" flag. If255 set, this flag indicates to the kernel that power should not256 be removed entirely from the device.257 258 Not all drivers support this attribute. If it isn't supported,259 it is not present.260 261 This attribute has no effect on system-wide suspend/resume and262 hibernation.263 264What: /sys/devices/.../power/runtime_status265Date: April 2010266Contact: Rafael J. Wysocki <rjw@rjwysocki.net>267Description:268 The /sys/devices/.../power/runtime_status attribute contains269 the current runtime PM status of the device, which may be270 "suspended", "suspending", "resuming", "active", "error" (fatal271 error), or "unsupported" (runtime PM is disabled).272 273What: /sys/devices/.../power/runtime_active_time274Date: Jul 2010275Contact: Arjan van de Ven <arjan@linux.intel.com>276Description:277 Reports the total time that the device has been active.278 Used for runtime PM statistics.279 280What: /sys/devices/.../power/runtime_suspended_time281Date: Jul 2010282Contact: Arjan van de Ven <arjan@linux.intel.com>283Description:284 Reports total time that the device has been suspended.285 Used for runtime PM statistics.286 287What: /sys/devices/.../power/runtime_usage288Date: Apr 2010289Contact: Dominik Brodowski <linux@dominikbrodowski.net>290Description:291 Reports the runtime PM usage count of a device.292 293What: /sys/devices/.../power/runtime_enabled294Date: Apr 2010295Contact: Dominik Brodowski <linux@dominikbrodowski.net>296Description:297 Is runtime PM enabled for this device?298 States are "enabled", "disabled", "forbidden" or a299 combination of the latter two.300 301What: /sys/devices/.../power/runtime_active_kids302Date: Apr 2010303Contact: Dominik Brodowski <linux@dominikbrodowski.net>304Description:305 Reports the runtime PM children usage count of a device, or306 0 if the children will be ignored.307 308